Validation of a Modified Rotterdam Symptom Checklist for Use with Cancer Patients in the United States

Transcription

1 Vol. 26 No. 5 November 2003 Journal of Pain and Symptom Management 975 Original Article Validation of a Modified Rotterdam Symptom Checklist for Use with Cancer Patients in the United States Kevin D. Stein, PhD, Maxine Denniston, MSPH, Frank Baker, PhD, Mary Dent, MA, Danette M. Hann, PhD, Sally Bushhouse, PhD, and Michele West, PhD American Cancer Society Behavioral Research Center (K.D.S., M.D., F.B., M.D., D.M.H.), Atlanta, Georgia; Minnesota Department of Health (S.B.), Minneapolis, Minnesota; and State Health Registry of Iowa (M.W.), Iowa City, Iowa, USA Abstract The Rotterdam Symptom Checklist (RSCL) is a well-known instrument for the assessment of symptom-related distress among cancer patients. Despite its broad application, the utility of the RSCL with patients of some cancers is hindered by the omission of several important physical symptoms and methodological limitations of previous validation studies. The aims of the present study were to modify the RSCL through the addition of several physical symptoms and to subsequently validate the modified version of the Rotterdam Symptom Checklist (RSCL-M) with a heterogeneous sample of cancer patients from the United States. A total of 1,005 male and female cancer patients from two midwestern states completed the RSCL-M and several other self-report instruments. Results indicated that the RSCL-M is a reliable and valid instrument for use with cancer patients in the United States and is sensitive to differences in physical distress across groups expected to have distinct symptomrelated distress profiles. J Pain Symptom Manage 2003;26: U.S. Cancer Pain Relief Committee. Published by Elsevier Inc. All rights reserved. Key Words Cancer, symptom assessment, quality of life Introduction Cancer patients experience elevated levels of physical and emotional distress due to side effects of noxious treatments, such as chemotherapy and radiation therapy, as well as from symptoms of the disease process itself. 1 Such symptom-related distress has been found to have a negative impact on cancer patients quality of Address reprint requests to: Kevin D. Stein, PhD, American Cancer Society, Behavioral Research Center, 1599 Clifton Rd., Atlanta, GA , USA. Accepted for publication: March 5, U.S. Cancer Pain Relief Committee Published by Elsevier Inc. All rights reserved. life 2 and may reduce compliance with treatment recommendations. 3 Consequently, the assessment of symptom-related distress has become a critical component of both clinical practice and research protocols with cancer patients. Several tools have been developed to assess symptomrelated distress, including the Symptom Distress Scale, 4 the Memorial Symptom Assessment Scale, 2 the M.D. Anderson Symptom Inventory, 5 and the Rotterdam Symptom Checklist. 6 The Rotterdam Symptom Checklist (RSCL) in particular has been used extensively with cancer patients in several countries 7,8 and has been endorsed by the United Kingdom Medical /03/$ see front matter doi: /s (03)00321-x

2 976 Stein et al. Vol. 26 No. 5 November 2003 Council as a useful tool in quality of life assessment. 9 In addition, the reliability and factorial structure of the RSCL have been examined in a variety of medical settings and with different patient populations Despite the fact that this measure has enjoyed widespread clinical use and research application, the authors of the present study believed that the overall utility, psychometric evaluation, and validation of the RSCL could be improved in several ways. Specifically, through the addition of several items, the utility and breadth of the RSCL could be extended, especially as it applies to the assessment of physical distress in patients of varied cancer diagnoses. Secondly, removal of the 8-item psychological dimension of the RSCL could minimize redundancy with other measures of emotional functioning often included in psychosocial research protocols. Finally, limitations in the methodology and samples of previous RSCL validation studies could be addressed through the inclusion of a more heterogeneous sample of cancer patients from the United States and the use of more appropriate comparison measures. A review of currently available measures as well as discussions with cancer treatment providers and consideration of the authors own clinical experience with cancer patients suggested that the RSCL, in its original form, did not assess the full spectrum of physically distressing symptoms experienced by cancer patients. Therefore, we attempted to improve the breadth and utility of the RSCL through the addition of several key physical symptoms. These efforts identified a number of symptoms experienced by cancer patients that do not appear on the original RSCL. In particular, symptoms such as weight loss, weight gain, and problems with bowel function are often reported by patients with colorectal cancer. 13,14 In addition, impotence and incontinence among prostate cancer patients have also been well documented Finally, patients with skin melanoma may experience skin irritations, whereas patients with lung cancer may suffer from chronic cough and difficulty breathing. 18,19 In contrast with the RSCL, several of the symptoms listed above are included on other commonly used symptom distress scales. For example, the symptom cough is included on both the Symptom Distress Scale 4 and the Memorial Symptom Assessment Scale, 2 whereas bowel difficulties and feeling bloated appear on the Symptom Distress Scale 4 and the M. D. Anderson Symptom Inventory. 5 The symptoms problems with urination, weight loss, and weight gain are also measured by the Memorial Symptom Assessment Scale. 2 It may be that these symptoms were not included on the RSCL due to the fact that the original validation sample upon which the scale was developed included primarily female breast and ovarian cancer patients. 6 Nevertheless, the omission of these symptoms from the RSCL suggests that important information regarding the range and severity of symptom-related distress may not be available when this scale is used with certain cancer populations. The six symptoms identified through these efforts (weight loss, weight gain, problems controlling your urine, problems controlling your bowels, skin irritation, and cough) were, therefore, added to the RSCL, resulting in a revised instrument that is hereafter referred to as the Modified Rotterdam Symptom Checklist (RSCL-M) (Appendix 1). In addition to adding six physical distress items to the RSCL, the eight items from the RSCL that measure psychological distress were not included in the RSCL-M used in the present study. The RSCL psychological distress items were omitted from the RSCL-M for two reasons. First, we wanted to avoid placing additional burden on cancer patients by significantly lengthening the measure. As we felt the addition of the six items was important to improving the breadth of the physical dimension, discarding the eight items from the RSCL psychological dimension represented a method by which the scale could maintain a reasonable length. Second, the battery of instruments used in the present study already included a mental health scale, the Profile of Mood States-Short Form, that we believed provided a more comprehensive assessment of emotional distress. The questionnaire also included several other instruments that contain items that assess emotional functioning. Inclusion of both a mental health scale and the psychological dimension of the RSCL would have resulted in unnecessary overlap and redundancy with respect to the assessment of emotional distress in our questionnaire. Consequently, additional burden would have been placed on study participants, and this might have resulted in respondent fatigue and perhaps failure to complete

3 Vol. 26 No. 5 November 2003 Validation of a Modified Rotterdam Symptom Checklist 977 the survey instrument. Because mental health measures are often included in psychosocial research protocols, it was also considered that other researchers could benefit from having an available tool to assess physical distress that did not include items that assess emotional distress. Scales often used in psychosocial research, such as the Profile of Mood States, the Center for Epidemiologic Studies-Depression, 23 and the Hospital Anxiety and Depression Scale, 24,25 provide more comprehensive data regarding psychological functioning and are also more sensitive to sub-clinical levels of emotional distress. Thus, when used in a clinical setting or included in psychosocial research protocols, such mental health scales negate the need for the assessment of emotional distress by the symptom distress scale. It should be noted, however, that the psychological distress scale of the RSCL may be useful under circumstances where other measures of emotional distress are not included or when patient burden is not an issue. In addition to the omission of important physical symptoms, the utility of the original version of the RSCL has been further limited by several sampling and methodological weaknesses of previous validation studies. To begin with, the psychometric properties of the RSCL have not been thoroughly investigated with cancer patients from the United States, leaving the efficacy of this scale with patients in this country yet to be determined. In fact, a review of the literature revealed that the majority of the RSCL studies have been conducted with European samples. For example, publications describing the original development 6 and subsequent validation 12 of the RSCL were based upon data collected from cancer patients in The Netherlands and the United Kingdom. Spanish and Italian versions of the RSCL have also been developed with cancer patients from their respective countries. 26,27 Although the cross-cultural feasibility and reliability of the RSCL have been investigated via a multinational clinical trial, 10 patients from the United States were not included in the study, nor could we identify any study that evaluated the psychometric properties of the RSCL with American cancer patients. Evaluation of the modified version of the RSCL (RSCL-M) with cancer patients in the United States was, therefore, an important objective in this study. Aside from utilizing predominantly European samples, other limitations of previous RSCL validation studies have been identified. 12 Specifically, primarily female (breast and ovarian cancer) patients treated with chemotherapy were included in the original RSCL validation study. 6 Subsequently, Watson and colleagues 12 addressed this issue by conducting a second RSCL validation study that included both male and female cancer patients with a variety of cancer diagnoses. Unfortunately, the study included sample sizes for some cancer diagnoses that were too small to allow for comparisons across cancer type. Furthermore, like the original validation study, 6 Watson and colleagues also only included patients treated with chemotherapy, so comparison of the RSCL across patients receiving different treatment modalities was not possible. As Watson and colleagues suggest, examination of the RSCL with samples that include patients with varied cancer diagnoses and treatment profiles is needed. 12 To address this issue, efforts were made to include sufficient numbers of patients with a wide range of both cancer diagnoses and treatment modalities in the present study. A final shortcoming of previous RSCL validation studies is that they generally have not included standard measures of physical functioning for the purpose of cross-validating the instrument. Instead, de Haes and colleagues 6 cited the results of a series of principal component analyses as support for the validity of the instrument. In later work, Watson et al. 12 compared the RSCL to the Hospital Anxiety and Depression Scale (HADS) 25 and the Psychosocial Adjustment to Illness Scale (PAIS) 28 in an effort to establish the validity of the RSCL. The use of such psychological measures for validation of the RSCL is rather puzzling when one considers that only 8 of the 30 items from the original RSCL measure psychological distress, whereas the other 22 items are said to represent physical distress. Due to its weighting toward the inclusion of items that assess physical rather than psychological distress, more confidence in the validity of the RSCL would have been afforded by examining the degree to which it correlated with established measures of physical functioning. As a result, we chose to use measures of physical functioning to assess the validity of the RSCL-M.

4 978 Stein et al. Vol. 26 No. 5 November 2003 In the present study, we sought to address the above-noted limitations of the original RSCL by 1) modifying the RSCL through the addition of several physical symptoms experienced by cancer patients that were not included on the original RSCL while also excluding the psychological symptoms that can be more thoroughly assessed with other instruments; 2) evaluating the psychometric performance of the modified Rotterdam Symptom Checklist (RSCL-M) in a sample of cancer patients from the United States; 3) including in the sample both male and female cancer patients with a broad range of cancer diagnoses and who were treated with variety of major cancer treatment regimens (i.e., surgery, chemotherapy, or radiation therapy) or some combination thereof; and 4) establishing the validity of the RSCL-M via comparisons to measures of physical functioning. Methods Modification of Rotterdam Symptom Checklist The original version of the Rotterdam Symptom Checklist developed by de Haes et al. 6 includes 30 items intended to measure distress associated with symptoms reported by cancer patients. On the basis of a series of principal component analyses, the RSCL was judged to represent two dimensions: psychological distress and physical distress. The psychological distress dimension consists of 8 items (irritability, worrying, depressed mood, nervousness, desperate feelings about the future, tension, anxiety, and problems concentrating); the remaining 22 items are included on the physical distress dimension. Patients are instructed to rate the extent to which each symptom has bothered them either during the past 3 days or the past week. Response categories include not at all, a little, quite a bit, and very much. While retaining the same response categories and referent time frame (past week) as the RCSL, the current study modified the original 30-item instrument by adding 6 items that assess physically distressing symptoms often experienced by cancer patients both during and after treatment. As noted previously, these items were identified via review of relevant literature and currently available symptom-distress scales, discussions with healthcare providers, and the authors own clinical experience with cancer patients. The items added were weight loss, weight gain, problems controlling your urine, problems controlling your bowels, skin irritation, and cough. Finally, in an effort to avoid lengthening the scale and to reduce the level of redundancy with other measures in our questionnaire battery, the 8-item psychological distress dimension of the original RSCL was not included in the modified Rotterdam Symptom Checklist (RSCL-M) used in the current study. Thus, the RSCL-M includes a total of 28 items. Procedures The data presented in this article were collected during the implementation pilot study for a large-scale population-based investigation of quality of life in cancer patients conducted by the intramural Behavioral Research Center of the American Cancer Society. To be included in the study, participants had to 1) be diagnosed with one of the 10 most commonly occurring cancers (bladder, female breast, colorectal, kidney, lung, skin melanoma, non- Hodgkin s lymphoma, ovarian, prostate, or uterine); 2) have Stage I-IV cancer at the time of diagnosis, with the exception of bladder cancer, for which in situ cases were also eligible; 3) have been at least 18 years of age at the time of diagnosis; 4) have no known physical, psychological, or neuropsychological disorders that would preclude them from participating (identified by their physician); and 5) be able to give written informed consent before study entry. Population-based samples of patients meeting the above eligibility criteria were selected by the state cancer registries of Iowa and Minnesota. Institutional Review Board (IRB) approval was obtained from the state health departments in both states. Prior to contacting selected cases, consent to approach the patient was solicited by mail from each selected patient s physician of record. A passive physician consent process was used such that if the physician did not indicate within 3 weeks of notification that a particular patient should not be contacted, consent to contact the patient was assumed. Once it was determined that physician consent to contact a given patient had not been denied, cancer registry staff mailed the patient a study description and two copies of an informed consent form. The patient was asked to sign and return one copy of the consent form, indicating whether or not they would participate in the

5 Vol. 26 No. 5 November 2003 Validation of a Modified Rotterdam Symptom Checklist 979 study. Non-response follow-up included a second mailing of study materials and telephone contact. Patients who provided written consent to be in the study were then mailed a study questionnaire. Of the 3,228 patients selected, 416 (13%) were found to be deceased, and an additional 76 (2%) were excluded because it was discovered that they did not meet study eligibility criteria. Of the remaining 2,736 patients, 129 (5%) were not contacted because their physician indicated some reason why they should not be approached. Of those patients for whom the physician did not deny consent to contact, an additional 1,198 (46%) declined to participate, resulting in 1,249 patients who provided written informed consent, 80% of whom returned a completed questionnaire. Thus, complete study data are available for 1,005 patients. Measures In addition to the RSCL-M, several other measures were included in the battery of instruments administered. These instruments were included in order to obtain necessary medical, demographic, and psychosocial information about the study participants as well as to establish convergent and discriminant validity of the RSCL-M. Data presented in this study were based on the following instruments: Medical/Demographic Questions. A standard set of questions regarding cancer diagnosis and treatment, presence of other comorbid medical conditions, and general demographic information such as age, sex, race/ethnicity, marital status, education, and income. MOS-SF-36 Physical Functioning (PF) and General Health (GH) Scales. Two scales from the Medical Outcomes Study (MOS) 36-item Short Form, 29 a self-administered questionnaire of health status for use in large-scale patient surveys. The Physical Functioning (PF) Scale includes 10 items that ask about the extent to which the respondents health has limited their physical activities during the last 4 weeks. PF response categories range from 1 (limited a lot) to 3 (not limited at all). The General Health (GH) Scale includes 5 items that ask about respondents perception of their general health. Four of the GH items employ a 1 (definitely true) to 5 (definitely false) response format; the remaining GH item uses a 1 (excellent) to 5 (poor) response format. Alpha coefficients for the PF and GH scales in the present study were 0.93 and 0.83, respectively. The two MOS scales were included in order to establish convergent validity of the RSCL-M. The Multidimensional Scale of Perceived Social Support (MSPSS). A 12-item self-report measure of subjectively assessed social support that includes 3 subscales (Family, Friends, and Significant Other), each of which address a different source of social support. 30 The MSPSS response format ranges from 1 (very strongly agree) to 7 (very strongly disagree) and is not keyed to a particular time frame. Alpha coefficients for the Family, Friends, and Significant Other subscales in the present study were 0.95, 0.94, and 0.96, respectively. When combined, the reliability remained excellent, with an overall alpha coefficient of The MSPSS was included in order to establish discriminant validity of the RSCL-M. The Functional Assessment of Chronic Illness Therapy-Spiritual Well-Being Scale (FACIT-Sp). A 12-item self-administered measure of spiritual well-being among patients with a chronic illness, including cancer. 31,32 Responses to the FACIT-Sp range from 0 (not at all) to 4 (very much) with respect to the extent to which the respondent endorses each statement during the past 7 days. The alpha coefficient for the FACIT-Sp in the current study was The FACIT-Sp was included in order to establish discriminant validity of the RSCL-M. Data Analysis The data were analyzed using SPSS version Descriptive statistics (frequencies, percentages, means, and ranges) were generated to characterize the study sample in terms of sociodemographic and medical parameters. Factor analytic techniques (principal component analysis) and hierarchical linear regression analyses were used to evaluate the contribution and utility of the 6 items added to the original 22-item RSCL physical dimension. The reliability of the RSCL-M was measured by calculating the internal consistency (coefficient alpha) for the sample as a whole as well as for individual cancer sites and treatment profiles. As previous studies have identified the need to examine the psychometric properties of the

6 980 Stein et al. Vol. 26 No. 5 November 2003 RSCL with both male and female cancer patients, 12 we calculated separate alpha coefficients for both sexes as well. Additional reliability analyses included the inspection of the alpha-if-item-deleted value for each RSCL- M item as well as a comparison of the internal consistency of the 28-item RSCL-M to that of the 22-item physical dimension of the original RSCL. The validity of the RSCL-M was evaluated through comparisons with other measures of conceptually similar constructs (convergent validity) and with measures of conceptually dissimilar constructs (discriminant validity). Pearson correlation coefficients were computed to evaluate the degree of association between the RSCL-M and the other instruments. Consistent with Campbell and Fiske, 33 it was predicted that the RSCL-M would show moderate-to-high correlations with measures of similar constructs but would show a weak correlation with measures of dissimilar constructs. As with the reliability analyses, the validity analyses were repeated separately for male and female patients in our sample. Finally, the sensitivity of the RSCL-M to differences in physical distress was evaluated by comparing mean RSCL-M scores across people of different cancer diagnoses, treatment categories, sex, and active versus completed treatment status. We hypothesized that patients with more debilitating cancers, such as lung cancer, would report greater symptom-related distress than those with less symptomatic diseases, such as skin melanoma and prostate cancer. Likewise, those patients treated with more symptom-inducing medical regimens, such as chemotherapy and radiation therapy, were expected to report more symptom-related distress than patients treated with surgery alone. It was also hypothesized that male and female cancer patients would report a different pattern of symptom-related distress. Indeed, Watson et al. 12 found in their study that, compared with the male cancer patients, female cancer patients showed a tendency to report greater symptomrelated distress. Patients still undergoing active treatment were expected to show more overall symptom distress as well as different patterns of symptom distress as compared to patients who reported they had completed treatment. Analysis of covariance (ANCOVA) was used to estimate the sensitivity of the RSCL-M to differences in physical distress among individuals of a different diagnosis and different treatment profile, above and beyond the impact of relevant medical and demographic variables. Independent sample t-tests were used to evaluate the sensitivity of the RSCL-M to differences in symptom distress among male and female cancer patients in the sample as well as to compare patients in active treatment to the those who had completed treatment (treatment status). A final analysis compared ratings of distress associated with individual RSCL-M items across cancer type, treatment modality, sex, and treatment status. This analysis was conducted to evaluate the potential for the creation of diseaseand treatment-specific modules of the RSCL-M. Results Sample Characteristics The 1,005 patients for whom complete data are available ranged in age from 19 to 92 (mean 58; SD 14). As shown in Table 1, slightly more than half of the participants were women (57%) and had graduated from high school (55%) while the vast majority were white (97%) and currently married (78%). Median household income was in the US$ 40,000 to US$ 74,000 range. As described above, patients of the 10 most common cancers were included in the sample with stratification by cancer diagnosis and age being conducted prior to case selection. Although differences in the number of patients of each cancer diagnosis were found due to varied rates of sampling and questionnaire completion, adequate numbers of patients from each cancer site were present in the sample for comparisons across cancer type. As shown in Table 2, prostate cancer patients represented the highest percentage (13%), followed by breast (12%), non-hodgkin s lymphoma (10%), ovarian (10%), colorectal (9%), uterine (9%), skin melanoma (8%), lung (8%), kidney (7%), and, finally, bladder (5%) cancer. Nine percent of the patients indicated that they had multiple cancer diagnoses. In addition to the type of cancer, data were also collected regarding the type of treatment received. The majority of patients (94%) received surgery, chemotherapy, radiation therapy, or some combination of the three. Table 2 shows the distribution of patients in each

7 Vol. 26 No. 5 November 2003 Validation of a Modified Rotterdam Symptom Checklist 981 Table 1 Demographic Characteristics Men n 428 (43%) Women n 574 (57%) Total n 1005 a Age Mean (SD) 60 (13) 56 (14) 57.7 (14) Range Marital status Marriage/marriage-like 374 (88%) 408 (72%) 782 (78%) Education 8 th grade 20 (5%) 16 (3%) 37 (4%) Some high school 34 (8%) 35 (6%) 69 (7%) High school or GED 133 (32%) 205 (36%) 338 (34%) Some college/vocational 111 (26%) 170 (30%) 281 (28%) College graduate 70 (17%) 87 (15%) 157 (16%) Professional 52 (12%) 53 (10%) 105 (11%) Household yearly income $5,000 3 (1%) 6 (1%) 9 (1%) $5,000 $9, (3%) 24 (5%) 35 (4%) $10,000 $19, (12%) 72 (14%) 116 (13%) $20,000 $39, (31%) 143 (29%) 262 (30%) $40,000 $74, (31%) 179 (36%) 296 (34%) $75, (22%) 73 (15%) 158 (18%) Race/Ethnicity b White 417 (97%) 558 (96%) 975 (97%) African American 3 (0.7%) 2 (0.2%) 5 (0.5%) Asian 1 (0.2%) 2 (0.3%) 3 (0.3%) Multi/other 2 (0.9%) 7 (1.9%) 9 (0.9%) Hispanic origin 0 6 (0.6%) 6 (0.6%) a Three subjects did not indicate sex. b Subjects were able to choose more than one category. of the treatment categories. Patients in these treatment categories may have also received immunotherapy, hormone therapy, or bone marrow transplantation. A small percentage (less than 2%) of patients did not receive surgery, chemotherapy, or radiation, but were treated with immunotherapy, hormone therapy, or bone marrow transplantation only. As Table 2 Cancer and Health-Related Variables Men n 428 (43%) Women n 574 (57%) Total n 1005 a Site of Cancer Bladder 43 (10%) 11 (2%) 54 (5%) Breast 1 (0.2%) 120 (21%) 121 (12%) Colorectal 46 (11%) 45 (8%) 91 (9%) Kidney 39 (9%) 32 (5%) 71 (7%) Lung 40 (9%) 38 (7%) 78 (8%) Prostate 129 (30%) 129 (13%) Skin melanoma 43 (10%) 42 (7%) 85 (8%) NHL 39 (9%) 57 (10%) 96 (10%) Ovarian 95 (17%) 95 (10%) Uterine 86 (15%) 86 (9%) Multiple/other sites 44 (11%) 42 (8%) 86 (9%) Cancer Treatment None indicated 28 (7%) 25 (4%) 53 (5%) Surgery 249 (58%) 250 (44%) 499 (50%) Radiation 21 (5%) 10 (2%) 31 (3%) Chemotherapy 28 (6%) 37 (6%) 65 (7%) Surgery and radiation 13 (3%) 64 (11%) 77 (7%) Surgery and chemotherapy 35 (8%) 113 (20%) 148 (15%) Chemotherapy and radiation 15 (4%) 24 (4%) 39 (4%) Surgery, radiation, and chemotherapy 26 (6%) 50 (9%) 76 (8%) Other (hormonal, BMT, etc.) 13 (3%) 1 (0.2%) 14 (1%) Cancer Treatment Completed 307 (72%) 383 (67%) 690 (69%) Sum of Comorbid Conditions 1.54 (0.08) 1.42 (0.08) 1.48 (0.054) a Three subjects did not provide information on sex.

8 982 Stein et al. Vol. 26 No. 5 November 2003 this group represented such a small percentage of the total sample and could not be grouped together meaningfully, they were not included in any analyses utilizing the treatment variable. Data regarding type of treatment was not available for 5% of the patients. Of the 1,005 participants in the study, 690 (69%) reported that they had completed cancer treatment at the time of data collection, 180 (18%) reported they were still undergoing treatment at the time of data collection, and 133 (13%) did not indicate whether or not they had completed treatment at the time of data collection. Evaluation of the Modification to the RSCL As discussed above, the RSCL-M used in the present study included the addition of 6 items measuring distress associated with common physical symptoms of cancer and its treatment that were not included in the original RSCL. Therefore, our first goal was to determine if the addition of these items was justified. We evaluated the addition of the six items in two ways. Our first task was to determine the extent to which the six new items were measuring the same construct as the 22 items from the original RSCL. To answer this question, we conducted a factor analysis of the 28 items from the RSCL-M. The results of a principal components analysis demonstrated that all 28 items loaded significantly on one general factor. Overall, the factor loadings ranged from (vomiting) to (lack of energy). The factor loadings for the six items added in the present study ranged from (weight gain) to (cough), suggesting these new items were not measuring a conceptually distinct dimension, as compared to the other 22 items in the scale. Our second task was to determine the contribution of the new items relative to the physical domain scale of the original RSCL. Specifically, we were interested in seeing whether the addition of six items to the 22-item physical domain of the RSCL improved the scale s ability to capture important information about physical distress among cancer patients. To evaluate this question, we conducted a hierarchical linear regression analysis with a measure of physical health, the Physical Health (PF) scale of the MOS-SF-36, as the dependent variable. In the first step, we entered the 22-item physical domain scale of the RSCL. Then, in the second step, we entered the six items that were added in the present study. As displayed in Table 3, the 22-item RSCL physical domain scale entered in Step 1 of the hierarchical linear regression analysis accounted for 33% of the variance in the MOS SF-36 PF scale. The entry of the six additional RSCL-M items in Step 2 resulted in a significant change in the R 2, with an additional 2% of the variance in the MOS SF-36 PF scale accounted for by the six new items above and beyond the variance attributable to the items in the first step. Reliability of the RSCL-M As demonstrated by the coefficient alpha shown in Table 4, the RSCL-M demonstrated excellent reliability for the sample as a whole (α = 0.88) as well as for the 10 cancer types (range in α ) and seven treatment modality groups (range in α ) included in these analyses. Additional analyses also showed the RSCL-M to be equally reliable with male (α 0.87) and female (α 0.89) cancer patients. In addition, each of the six additional physical distress items added to the instrument was found to be significantly related (via item-total correlation) to the total scale, demonstrating internal consistency with the 22 items from the physical dimension of the original RSCL. Furthermore, an inspection of the alpha-if-item-deleted values demonstrated that no individual items either significantly add or detract from the overall reliability estimate. Specifically, whereas the overall alpha for the RSCL-M was , the alpha-if-item-deleted values ranged from to , including the 6 new RSCL-M items. Finally, we calculated the coefficient alpha for the original 22-item RSCL physical domain scale alone and found no Table 3 Hierarchical Regression of RSCL Scales on MOS Physical Functioning Score Steps/ Predictors R 2 R 2 change F df β 1 β 2 1. Physical a 1, a 0.47 a domain of RSCL 2. Six new a 1, a items from RSCL-M β 1 standardized regression coefficient for equation #1; β 2 standardized regression coefficients for equation #2; df degrees of freedom. a P

9 Vol. 26 No. 5 November 2003 Validation of a Modified Rotterdam Symptom Checklist 983 Table 4 Reliability of Modified Rotterdam Symptom Checklist Cronbach s alpha Entire sample 0.88 Sex Men 0.87 Women 0.89 Site of cancer Bladder 0.83 Breast 0.89 Colorectal 0.87 Kidney 0.90 Lung 0.87 Prostate 0.86 Skin melanoma 0.89 NHL 0.88 Ovarian 0.88 Uterine 0.89 Multiple/other 0.86 Treatment regimen Surgery 0.88 Radiation 0.93 Chemotherapy 0.90 Surgery and radiation 0.92 Surgery and chemotherapy 0.86 Chemotherapy and radiation 0.86 Surgery, radiation, and 0.88 chemotherapy Other 0.86 marked differences from the alphas computed with the RSCL-Mfor thesample as awhole, as well as across cancer type, treatment modality, or sex. Validity of the RSCL-M As noted previously, both convergent and discriminant validity were examined in order to establish the overall validity of the RSCL-M. Convergent validity was assessed by examining the association between the RSCL-M and two other measures of physical health: the Medical Outcomes Study 36-item Short Form (MOS SF- 36) Physical Functioning (PF) and General Health (GH) scales. Discriminant validity was assessed by examining the relationship of the RSCL-M to two instruments that were considered to measure conceptually different constructs from physical distress. These instruments were the Multidimensional Scale of Perceived Social Support (MSPSS), a measure of social support; and the Functional Assessment of Chronic Illness Therapy-Spiritual Well-Being Scale (FACIT-Sp), a measure of spirituality. As shown in Table 5, the results of these correlational analyses demonstrated that the RSCL- M was moderately correlated with both the MOS-SF-36 PF scale (r 0.59) and the MOS- SF-36 GH scale (r 0.61). In contrast, the RSCL-M was found to have weak correlations with the MSPSS (r 0.21) and the FACIT-Sp (r 0.31). The negative correlations between the RSCL-M and the other measures reflect the fact that high scores on the RSCL-M indicate more physical distress, whereas high scores on the other scales indicate better functioning in each of the respective domains they measure. In addition, as with the examination of reliability, validity analyses conducted separately with male and female patients showed the same pattern of results as with the sample as a whole (see Table 5). Sensitivity of the RSCL-M To evaluate the sensitivity of the RSCL-M to differences in physical distress, mean RSCL-M scores were compared across patients with different cancer diagnoses, treatment profiles, sex, and treatment status (active vs. completed). First, we examined the sensitivity of the RSCL- M to differences in physical distress among patients with different cancer diagnoses by conducting an analysis of covariance (ANCOVA) with mean RSCL-M scores as the dependent variable and age and prevalence of other comorbid conditions treated as covariates. Age and prevalence of comorbid conditions (as measured by the sum of comorbid conditions reported) were selected for inclusion in the model because they were the only medical/ demographic variables significantly (P 0.05) correlated with the RSCL-M total score. This analysis allowed for the evaluation of the influence of cancer type on symptom distress above and beyond the impact of relevant medical and demographic variables. Patients who reported that they were diagnosed with more than one Table 5 Convergent and Discriminant Validity Men Women Total n 428 n 574 n 1005 a Convergent Validity (Pearson s r) MOS SF-36 Physical Functioning Subscale MOS SF-36 General Health Subscale Discriminant Validity (Pearson s r) MSPSS FACIT-Sp a Three subjects did not provide information on sex.

10 984 Stein et al. Vol. 26 No. 5 November 2003 type of cancer (n 90) were not included in these analyses. The results of the ANCOVA indicated a significant difference in physical distress (F 7.060, df 9, P 0.001) across the 10 cancer diagnoses, even after controlling for the influence of age and comorbidities. Posthoc analyses revealed that the diseases sites associated with the most physical distress were lung cancer and non-hodgkin s lymphoma, whereas bladder and skin melanoma cancer patients were shown to have to have the least amount of physical distress (see Table 6 for means and post hoc multiple comparison tests). To examine the sensitivity of the RSCL-M to differences in physical distress by treatment modality, we conducted a second ANCOVA, again including age and prevalence of comorbid conditions as covariates due to their significant (P 0.05) relationship to the RSCL-M total score. Patients who reported receiving immunotherapy, hormone therapy, or bone marrow transplantation only (n 14) and those for whom treatment data were not available (n 53) were excluded from this analysis. The results of the ANCOVA indicated a significant difference in physical distress among patients with different treatment profiles (F , df 6, P 0.001), even after controlling for the influence of age and comorbidities. Post-hoc analyses revealed that patients Table 6 Comparisons of RSCL-M Scores by Cancer Type and Treatment Type a Mean (SEM) Cancer Type Skin Melanoma (0.93) a Bladder (1.14) a Prostate (0.75) a Breast (0.77) a Uterine (0.92) a Colorectal (0.88) b Kidney (0.99) b Ovarian (0.88) b NHL (0.86) c Lung (0.97) d Treatment Surgery (0.38) a Surgery and radiation (0.98) b Surgery, radiation, (0.99) b and chemotherapy Chemotherapy (1.05) b Radiation (1.64) b Surgery and chemotherapy (0.70) b Chemotherapy and radiation (1.35) c a a,b,c,d denote significantly different (P 0.05) means via Bonferroni adjustment of alpha. treated with surgery only reported the lowest amount of physical distress, whereas patients treated only with a combination of radiation and chemotherapy reported the greatest amount of symptom-related distress (see Table 6 for means and post hoc multiple comparison tests). The sensitivity of the RSCL-M to differences in symptom-related distress was also compared between male and female cancer patients as well as between those still undergoing active treatment and those who had completed treatment at the time of data collection. As expected, a comparison of mean RSCL-M scores demonstrated a significant gender difference in total symptom distress (t 3.957, P ), with women recording a higher mean RSCL-M score compared to men (39.98 vs ). A significant difference (t 3.677, P ) in mean RSCL-M scores was also found between patients in active treatment (mean 41.13) as compared to those who had completed treatment (mean 38.24). Once all comparisons of total RSCL-M scores across cancer type, treatment modality, sex, and treatment status had been completed, a final analysis examined which items were rated as most and least distressing. This analysis was conducted for the sample as a whole, as well as across cancer type, treatment modality, sex, and treatment status. For each of these categories, individual RSCL-M items were listed in order of highest to lowest mean scores. The results revealed that one cluster of symptoms consistently grouped together at the top (most distressing), while another cluster of symptoms consistently grouped together at the bottom (least distressing). Despite some minor fluctuations in the order of the items, a similar pattern was noted across each of the categories in which this analysis was conducted. Symptoms consistently rated as most distressing were tiredness, lack of energy, difficulty sleeping, and decreased sexual interest; symptoms consistently rated as least distressing were nausea, vomiting, sore mouth/swallowing, and weight loss. Average ratings for each RSCL-M item, collapsed across categories (i.e., for the sample as a whole) are exhibited in Table 7. Discussion The assessment of physical symptoms associated with cancer and its treatment can guide

11 Vol. 26 No. 5 November 2003 Validation of a Modified Rotterdam Symptom Checklist 985 Table 7 Ranking of RSCL-M Items by Mean from Most to Least Distressing (n 1005) Mean (SD) Tiredness Lack of energy Decreased sexual interest Difficulty sleeping Low back pain Sore muscles Weight gain a Heartburn/belching Problems controlling urine a Tingling hands/feet Shortness of breath Headaches Cough a Dry mouth Abdominal aches Constipation Loss of hair Problems controlling bowels a Skin irritation a Diarrhea Burning/sore eyes Dizziness Lack of appetite Shivering Weight loss a Nausea Sore mouth/swallowing Vomiting a Items added in current study. psychosocial intervention and is an important component in quality of life and clinical trials research. One of the most widely used instruments for symptom assessment is the Rotterdam Symptom Checklist (RSCL). The present study contributes to the body of research investigating the RSCL in several ways. First, through modification of the RSCL item content, the RSCL-M described presently assesses a broader and more comprehensive list of physical symptoms experienced by cancer patients while leaving the assessment of emotional distress to scales designed specifically for that purpose. In particular, the addition of physical symptoms associated with cancers of the lung, colon/ rectum, skin, and prostate extends the range of cancer patients with which the scale may be used. These new items were found to be reliable, to account for unique variance in physical health, and to be measuring the same general construct (physical distress) as the 22 items from the original RSCL. It should be noted, however, that although the increase in variance accounted for by the addition of the six physical distress items was statistically significant, a 2% increase may not be clinically significant. Despite this fact, both clinicians and researchers may find the new items allow for the use of the RSCL-M with a wider range of patients compared to the original RSCL. In addition, the removal of the 8-item psychological dimension of the RSCL produced a scale that avoids the pitfalls of item overlap, redundancy, and subject burden that may result when a symptom-distress scale is used in conjunction with other measures of emotional functioning, as is often the case in both psychosocial research and clinical practice. Although the omission of these items has obvious advantages, it may be appropriate to include the psychological items from the RSCL if no other measure of emotional functioning is included or when subject burden is not an issue. Future research should examine how well the psychological items from the original scale perform with cancer patients from the United States. The RSCL-M also has several advantages over other available symptom distress scales. In general, it includes a wider range of physical symptoms, is more specific, and is easier to complete. Although other scales are more general in that they attempt to assess both physical and emotional distress, the RSCL-M focuses specifically on the assessment of physical distress. In doing so, the RSCL-M may provide a more complete picture of physical symptom-related distress and may be used with a wider range of cancer patients. The response format of the RSCL-M is also easier to complete than some of the other frequently used symptom distress scales. For example, the Memorial Symptom Assessment Scale 2 requires the respondent not only to report the presence of a symptom, but also to rate the severity and distress associated with each symptom. Although this information can be valuable, it results in a scale this is significantly longer and more complicated and time consuming to complete. The results of the present study also indicate that RSCL-M is a valid and reliable tool in the assessment of symptom-related distress with cancer patients in the United States. The inclusion of cancer patients from the United States in the current validation sample represents a significant contribution to this literature, as the psychometric properties of the original version of the scale had not been investigated with this

12 986 Stein et al. Vol. 26 No. 5 November 2003 population previously. Furthermore, the methods used to establish validity used presently are based upon much firmer methodological ground than validations of the original RSCL. Specifically, the comparison of the RSCL-M to other measures of physical functioning affords greater confidence in the validity of the scale than previous validation studies that only investigated the association of the RSCL to measures of psychological functioning. Finally, the RSCL-M was shown to be useful with patients of varied medical and demographic characteristics, including both men and women diagnosed with a wide range of cancers and who have received the major cancer treatment regimens. Establishing the ability of the RSCL-M to be sensitive to differences in groups expected to have different symptom distress profiles underscores its utility in both research and clinical settings. In addition to these primary objectives, it was also of interest to determine if the RSCL-M could be tailored for use with different patient populations. Indeed, previous RSCL studies 6,12,34 have advocated the development of disease and treatment-specific modules to supplement a core set of RSCL items. As suggested by de Haes and colleagues, 6 an examination of the responses among patients of different genders, illnesses, and treatment modalities may reveal that the pattern and profile of symptom distress vary across patients with different medical and demographic characteristics. If identified, such differences may in turn suggest to both the clinician and the researcher which RSCL-M items are appropriate for use with particular patient populations to meet specific assessment needs. Ideally, such diseasespecific and treatment-specific versions of the RSCL-M would contain only those items relevant to patients with certain medical and demographic characteristics. In the current study, however, analyses of response patterns to individual items by patients of different diagnosis, treatment modality, sex, and treatment status did not reveal great differentiation among the items rated as most or least distressing. In fact, we found that regardless of these medical and demographic characteristics, participants consistently rated one cluster of symptoms as most distressing and another cluster as least distressing. This finding is perhaps not surprising given that over two-thirds of the participants in the current study had completed treatment at the time of data collection, when all but the most persistent symptoms are likely to have abated. In other words, it is possible that any differentiation among patient groups with respect to disease and/or treatment specific symptom profiles that might have been evident during treatment was no longer present when these data were collected. This hypothesis is supported by the finding that the symptoms consistently reported as being most distressing in the current sample, sexual dysfunction and fatigue-related problems, are known to be among the most persistent symptoms reported by cancer survivors. 35,36 Despite not finding evidence in the current study to support the tailoring of the RSCL-M among respondents, differences in the overall level of distress (as indicated by mean RSCL-M scores) were noted among patients with different diagnoses, treatments, sexes, and treatment status. These differences suggest that the RSCL- M is sensitive enough to be able to detect differences in physical distress among groups that would be expected to have different levels of symptom-related distress. A close inspection of the mean RSCL-M scores (see Table 6) suggests the differences in the magnitude of physical distress reported among individuals within these groups is not only statistically significant but is also clinically significant. Specifically, individuals with lung cancer were found to have a mean RSCL-M score more than 8 points higher than skin melanoma patients. Likewise, patients who received a combination of chemotherapy and radiation only reported a RSCL-M total score more than 9 points higher than patients treated with surgery only, on average. Each of these differences suggests patients with the highest RSCL-M scores were experiencing distress at almost a full standard deviation above those with the lowest RSCL-M scores. With respect to sex, data from the present study support the conclusion of Watson et al. that women may be more likely to report symptom-related distress than male cancer patients. 12 In contrast to the findings of Watson and colleagues, however, sex differences in self-reported distress were evident in the current study even after the completion of treatment, suggesting that the gender-based differences in reporting may