The Pennsylvania State University. The Graduate School. Department of Public Health Sciences

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1 The Pennsylvania State University The Graduate School Department of Public Health Sciences THE LENGTH OF STAY AND READMISSIONS IN MASTECTOMY PATIENTS A Thesis in Public Health Sciences by Susie Sun 2015 Susie Sun Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science May 2015

2 The thesis of Susie Sun was reviewed and approved* by the following: Christopher Hollenbeak Professor of Surgery and Public Health Sciences Thesis Advisor Anna Leung Assistant Professor of Surgery Division of Surgical Oncology Kristen Kjerulff Professor of Public Health Sciences Director of Master of Science in Public Health Sciences Program *Signatures are on file in the Graduate School

3 iii ABSTRACT Background. Interest is growing in preventing readmissions as payers start to link reimbursement to readmission rates. The purpose of this study was to assess factors that contribute to 30-day readmission rates for women undergoing mastectomy for breast cancer. Methods. Data from the Pennsylvania Health Care Cost Containment Council was queried for women undergoing mastectomy for breast cancer during 2011 (n=2,919). The outcomes measured were length of stay (LOS) and 30-day readmission. Univariate comparisons between characteristics of readmitted (n=172) and non-readmitted patients were performed using t tests and chi-square tests. Readmission was modeled using logistic regression; LOS was modeled using linear regression and controlled for potential confounders. Results. In multivariate analyses, patients with peripheral vascular disease were more likely to be readmitted (OR 4.36, p=0.002). Increased LOS was also associated with increased odds of readmission (OR 1.26, p=<0.0001). Since LOS was an important predictor of readmission we also estimated determinants of LOS using linear regression. The occurrence of reconstructive surgery (p=<0.0001) and renal disease (p<0.0001) were highly predictive of longer LOS. Conclusions. This study showed peripheral vascular disease and longer lengths of stay were associated with higher odds of readmission in women undergoing mastectomy. Clinicians should be cognizant that optimizing a patient s vascular status before mastectomy may lead to lower rates of readmission. Additional research is needed to determine whether the relationship between readmissions and length of hospital stay is a causative versus associative phenomenon since length of stay is a modifiable factor that may lead to lower readmissions.

4 iv TABLE OF CONTENTS LIST OF FIGURES... v LIST OF TABLES... vi ACKNOWLEDGEMENTS... vii Chapter 1 Introduction... 1 Surgical Treatment of Breast Cancer... 1 Outcomes of Breast Cancer Surgery... 1 Length of Stay and Readmissions Following Mastectomy... 2 Chapter 2 Methods... 3 Data Patient Selection... 3 Outcomes... 3 Covariates... 4 Statistically Analysis... 4 Chapter 3 Results... 8 Descriptive Statistics... 8 Readmission... 9 Length of Stay Chapter 4 Discussion s... 19

5 v LIST OF FIGURES Figure 3-1: Probability of readmission based on length of index hospital stay.... 6

6 vi LIST OF TABLES Table 3-1: Patient characteristics based on readmission status... 6 Table 3-2: Pre-operative patient comorbidities... 8 Table 3-3: Multivariate odds ratio of risk factors for 30-day readmission... 9 Table 3-4: Multivariate model of factors affecting length of stay.... 8

7 vii ACKNOWLEDGEMENTS Penn State Hershey Department of Surgery Dr. Peter Dillon Dr. David Han Dr. David Soybel

8 1 Chapter 1 Introduction Breast cancer is the second most commonly diagnosed cancer among American women, with 1 in 8 women developing invasive breast cancer during their lifetime. It is also the second leading cause of cancer deaths in women, after lung cancer. The American Cancer Society estimates that there will be 232,340 new cases of invasive breast cancer diagnosed in 2013 in women, with 64,640 new cases of carcinoma in situ and 39,620 deaths from breast cancer [1]. The incidence of breast cancer in Pennsylvania is one of the highest in the U.S. Between 2004 and 2008 the incidence was cases per 100,000 non-hispanic white women, cases per 100,000 African American women, and 96.9 cases per 100,000 Hispanic women. Surgical Treatment of Breast Cancer For patients without metastatic disease, surgery is the mainstay of treatment. This includes lumpectomy (partial mastectomy), lumpectomy with sentinel node biopsy, lumpectomy with axillary node dissection, simple mastectomy, modified radical mastectomy, radical mastectomy, unilateral and bilateral mastectomy. Recent studies show that the rate of mastectomy has increased within the past few years [2]. Outcomes of Breast Cancer Surgery The mortality and morbidity associated with mastectomy have been studied extensively. Most studies have compared differences between mastectomy and breast conserving therapy in

9 2 terms of mortality and morbidity. It has been shown that the mortality associated with both procedures is low. Hospital length of stay is higher in mastectomy patient than for breast conserving therapy [3]. The most commonly studied morbidity associated with breast surgery is wound complications. Readmission and Length of Stay Following Mastectomy There are only a few studies that estimate readmission rates for mastectomy or identify factors associated with readmission in women post mastectomy. But, readmission is becoming an important outcome as payers, particularly the Center for Medicare and Medicaid Services, are beginning to deny reimbursement for readmissions for some diseases [4]. The purpose of this study was to estimate 30-day readmission rate for women undergoing surgical treatment for breast cancer in Pennsylvania and determine factors associated with readmission.

10 3 Chapter 2 Methods Data The data set utilized was discharge data from the Pennsylvania Health Care Cost Containment Council (PHC4). The PHC4 database contains inpatient hospital discharge data for admissions to all hospitals and surgical facilities in Pennsylvania and includes patient demographics, diagnosis codes, procedures codes, and hospital information. Patient Selection Women over age 18 who had undergone mastectomy in 2011 were included in this study. Mastectomy was identified using the International Classification of Disease, 9 th Revision, Clinical Modification (ICD-9) procedure codes: (Unilateral simple mastectomy), (Bilateral simple mastectomy), (Unilateral extended simple mastectomy), (Bilateral extended simple mastectomy), (Unilateral radical mastectomy), (Bilateral radical mastectomy), and (Unilateral extended radical mastectomy). Outcomes The primary outcome assessed was readmission within 30 days of discharge from the initial hospital stay. Since previous studies have found that a longer hospital stay is associated with higher risk of readmission, we also studied the length of stay of the index admission [5-7].

11 4 Covariates Covariates included in the study were age (<45, 45-64, 65-74, >75), race (white, black, other), admission type (elective, urgent, and emergent), payer type (self-pay, HMO, commercial, Medicare), transfer status, type of mastectomy (unilateral, bilateral, simple, radical, extended), hospital volume, surgeon volume, reconstruction, and comorbidities. Hospital volume was stratified into high (>75) and low ( 75) volume centers, based on the median of our data. Surgeons who performed more than 25 mastectomies per year (the median) were considered high volume, and those who performed less than or equal to 25 were considered low volume. Comorbidities were assessed using the Charlson comorbidity index, which consisted of 17 comorbid conditions [8]. These included acute myocardial infarction, congestive heart failure, peripheral vascular disease, cerebral vascular disease, dementia, COPD, rheumatoid arthritis, peptic ulcer disease, mild liver disease, diabetes mellitus, diabetes with complications, hemiplegia, paraplegia, renal disease, cancer, moderate to severe liver disease, metastatic cancer, and AIDS. Statistically Analysis The statistical analysis was designed to determine variables that had a significant association with readmission within 30 days. We also studied specifically the relationship between length of stay (LOS) of the index hospitalization and risk of readmission. Patient demographics were compared between those readmitted and not readmitted using Student s t tests for continuous variables and chi-square tests for binary and categorical variables. Logistic regression was used to model 30-day readmission as a function of other covariates.

12 5 Goodness of fit of the logistic regression model was measured as the area under the Receiver Operating Characteristic (ROC) Curve. We also modeled length of hospitalization using linear regression, and controlled for potential confounders. All statistical analyses were performed using STATA software (version 10.1, StataCorp, College Station, TX, USA). Statistical significance was defined by p value <0.05.

13 6 Chapter 3 Results Descriptive Statistics A total of 2,919 female mastectomy patients were included in this study. Patient characteristics stratified by readmission status are reported in Table 3-1. There were no statistically significant differences between the readmitted and non-readmitted groups with respect to most patient demographics and clinical characteristics. However those who were readmitted were more likely to have been admitted urgently or emergently for their initial mastectomy (p=0.02). Patients who were not readmitted were more frequently treated by surgeons with a higher average volume of mastectomy cases (27.1 versus 21.6, p=0.006). The mean post-operative length of stay for the readmitted group was 3.2 days versus 2.1 days for the non-readmitted group (p<0.0001). Figure 3-1: Patient characteristics based on readmission status. Not readmitted Readmitted Variable (N=2747) (N=172) P-value Age < % 10.5% % 51.2% % 20.3% % 18.0% Race White 83.7% 81.4% Black 11.3% 14.5%

14 7 Other 5.0% 4.1% Admission type Elective 95.8% 91.3% Urgent 3.1% 6.4% Emergent 1.1% 2.3% Payer type Medicare 38.3% 41.9% Commercial 51.8% 47.1% Selfpay 0.2% 0.0% HMO 31.2% 29.1% Transfer Yes 1.0% 1.2% No 99.0% 98.8% Laterality Bilateral 26.4% 23.8% Unilateral 73.6% 76.2% Mastectomy type Simple 98.3% 98.3% Radical 1.7% 1.7% Extended 44.2% 44.2% Hospital Volume Low (<=75) High (>75) Surgeon Volume Low (<=25) High (>25) Reconstruction Yes 43.07% 41.86% No 56.93% 58.14% LOS <0.0001

15 Hospital and surgeon volumes presented as average number of mastectomies performed per year. Patient comorbidities stratified by readmission are reported in Table 3-2. When compared to the non-readmitted cohort, readmitted patients were more likely to have had higher total number of pre-operative comorbidities (1.4 vs. 1.2, p<0.0001). The readmitted cohort was also more likely to have had a number of specific comorbidities, including congestive heart failure (4.1% vs. 1.9%, p=0.049), peripheral vascular disease (4.1% vs. 0.9%, p<0.0001), COPD (15.7% vs. 10.3%, p=0.025), and renal disease (4.7% vs. 1.7%, p=0.005). 8 Table 3-2: Pre-operative patient comorbidities. Not readmitted Readmitted Variable (N=2747) (N=172) P-value Comorbidities AMI 2.2% 4.1% CHF 1.9% 4.1% PVD 0.9% 4.1% < CEVD 0.9% 1.2% COPD 10.3% 15.7% RA 1.7% 1.7% PUD 0.3% 0.6% DM 13.5% 16.9% Renal disease 1.7% 4.7% Total comorbidities < AMI: Acute myocardial infarction; CHF: Congestive heart failure; PVD: Peripheral vascular disease; CEVD: Cerebrovascular disease; COPD: Chronic obstructive pulmonary disease; RA: Rheumatoid arthritis; PUD: Peptic ulcer disease; DM: Diabetes mellitus

16 9 Readmission Of the 2,919 women who underwent mastectomy in 2011, 172 (5.9%) were readmitted within 30 days. Results from the logistic regression model of 30-day readmission are presented in Table 3-3. This model suggests that patients who had peripheral vascular disease were 4 times more likely to be readmitted than patients without peripheral vascular disease (p=0.002). Increased length of post-operative hospital stay was also associated with increased odds of readmission (OR 1.26, p=<0.0001). Patient demographics such as age, sex, race, type of mastectomy, whether or not reconstructive surgery was performed, hospital volume, and surgeon volume did not have statistically significant effects on risk of readmission. Table 3-3: Multivariate odds ratio of risk factors for 30-day readmission. 95% Confidence Variable OR Lower Upper P-value Age < Race White Black Other Admission type Emergent Urgent Elective Payer type Selfpay

17 10 HMO Commercial Medicare Transfer Yes No Bilateral vs Unilateral Bilateral Unilateral Mastectomy type Simple Radical Extended Comorbidities AMI CHF PVD CEVD COPD RA PUD DM Renal disease Hospital Volume Low (<=75) High (>75) Surgeon Volume Low (<=25) High (>25) Reconstruction Yes No LOS <0.0001

18 11 Area under the ROC curve = Figure 3-1 presents the fitted relationship between length of hospital stay and risk of readmission. After controlling for other factors, risk of readmission increased with the length of the index hospitalization. After controlling for other factors, a patient with a 5-day stay had a predicted probability of readmission within 30 days of 10.5%. A patient with a 15-day stay had a probability of 30-day readmission of 50.7% Probability of Readmission Length of Stay (Days) Figure 3-1: Probability of readmission based on length of index hospital stay. Length of Stay Since length of stay was an important determinant of risk of readmission, we also studied factors associated with hospital stay. Table 3-4 presents the results of the multivariate linear

19 12 regression model of total length of hospital stay. Black race (p<0.0001), radical mastectomy (p=0.013), emergent procedure (p<0.0001) and urgent procedure (p<0.0001) admission types were associated with longer LOS. Patient who underwent immediate reconstruction had a length of stay that was on average 1 day longer than those who did not have reconstruction (p<0.0001). Comorbidities such as congestive heart failure (p=0.04), rheumatoid arthritis (p=0.007), and renal disease (p=<0.0001) were predictive of longer lengths of stay. Patients with commercial insurance had shorter average hospital stays (p=0.03). Table 3-4: Multivariate model of factors affecting length of stay. 95% Confidence Variable Coefficient Lower Upper P-value Age < Race White Black < Other Admission type Emergent < Urgent < Elective Payer type Medicare Commercial Selfpay HMO

20 13 Transfer Yes No Bilateral vs Unilateral Bilateral Unilateral Mastectomy type Simple Radical Extended Comorbidities AMI CHF PVD CEVD COPD RA PUD DM Renal disease < Hospital Volume Low (<=75) High (>75) Surgeon Volume Low (<=25) High (>25) Reconstruction Yes < No Constant < R-squared =

21 14 Chapter 4 Discussion Surgical resection continues to be the cornerstone of treatment for breast cancer. This includes breast conservation therapy and mastectomy. Many studies have shown that breast conservation therapy has lower morbidity and mortality, including length of hospital stay and readmission rates, compared to mastectomy [3]. However despite increasing rate of mastectomy and changes in payer focus on readmissions, there are only a few studies that report on readmission rates for mastectomy patients [2]. The current study evaluated factors predictive of readmissions. Of the 2,919 patients included in this study, 172 (5.9%) were readmitted. Our predictive model showed that patients with peripheral vascular disease had 4 times higher odds of readmission. In addition to vascular disease, each additional day in length of index hospital stay led to a 26% increased odds of readmission. Analysis of other disease states such as heart disease, renal disease, and diabetes did not show statistically significant increases in odds of readmission. This is likely due to the relatively small sample size used in our analysis. Since our model showed that longer hospital stays led to increased odds of readmission, we then studied factors that increased length of index hospital stays. After adjusting for potential confounders, our analysis showed that black race, urgent or emergent surgeries, radical mastectomy, reconstruction, and certain comorbid conditions led to longer hospital stays. Immediate reconstruction following mastectomy led to a 1-day extension in stay. Renal disease had the largest impact by lengthening hospital stay by 1.68 days.

22 15 The association between increased length of stay and immediate reconstruction is consistent with previous studies [9]. Longer stays are expected since reconstruction often requires closer monitoring, especially for those who underwent reconstruction using tissue flaps. Reconstruction is also associated with increased risk for wound complications. Mortenson et al. showed an increased in the incidence of readmissions for cellulitis, wound infections, hematomas, and poor wound healing in those who underwent immediate reconstruction compared with those who did not [10]. Numerous studies have shown that black race is associated with more advanced breast cancers as well as decreased survival which may effect the type of mastectomy performed and contribute to longer hospital stays [11-13]. The current study showed that African Americans stayed on average 0.66 days longer than Caucasian patients. This is likely due to the multiple socioeconomic disadvantages that are encountered by the African American community which serve as barriers to breast cancer screening and treatment, which then leads to delayed presentation and more advanced cancers necessitating more complex surgical procedures and longer recovery time. Our study found that comorbid conditions, including congestive heart failure, rheumatoid arthritis and renal disease extended a patient s hospital stay. This is not unexpected, as comorbidities may lead to more postoperative complications and for the patient to be discharged to places other than home, thus causing prolonged hospitalizations in women undergoing breast surgery for cancer [14]. Collins et al. studied risk factors for prolonged length of stay in 11 major elective surgeries. They found that along with intra-operative and post-operative variables, preoperative factors such as age, functional status, and comorbid conditions were predictive of

23 16 longer lengths of stay [15]. Possibly due to our smaller sample size, we did not find age to be associated with prolonged hospitalization. Our data did show that certain comorbid condition were directly associated with longer hospital stays and risk for 30 day readmissions. There are many studies that assess risk factors of readmission for various general, colorectal and vascular surgery procedures but there are none that focus specifically on mastectomies. These studies also largely identified risk factors for readmission while the current study includes predictive models for readmission as well as factors that lengthen hospital stay. Our findings are consistent with previous studies that have shown the association between comorbid conditions with increased risk for readmission [5, 16-19]. We hypothesize that vascular disease may lead to readmission due to poor wound healing and higher infection risk. Several studies have also shown that longer length of stay is associated with increased risk for readmission [5, 17, 20]. This was consistent with our findings. However the current study concurrently evaluated readmissions and length of stay in the same cohort of patients. Figure 1 demonstrates the probability of readmission stratified by length of stay. For example, after controlling for other factors, a patient who was hospitalized for 5 days had a 10% probability of being readmitted within 30 days. This study made use of an administrative database and is thus subject to several limitations. The PHC4 database did not contain any information regarding each patient s cancer such as stage and type, which may affect both length of stay and readmission. Cancer stage can affect which type of mastectomy is performed, which can affect length of stay as demonstrated in our analysis. Patients with more advanced stage cancers may experience more complications and cancer related comorbidities leading to higher risk for readmissions and longer lengths of stay. Additionally, there could be potential confounding between urgent or emergent admission types

24 17 and stage of disease. Since non-elective breast surgery is relatively rare, one could postulate that patients admitted urgently or emergently were those who presented with necrotizing tumors, skin breakdown, and other predisposing factors to infection due to advanced stage breast cancer. The database also did not contain any information regarding post-operative complications. Studies have shown that complications increase length of stay and readmissions for both general and breast surgery patients [5, 14, 15]. Even though 30-day morbidity rates of mastectomy patients are relatively low, 5.72% as suggested by El-Tamer et al., it may still affect both length of stay and readmission risk [3]. There were no data available on neoadjuvant or postoperative chemotherapy, however studies have shown that they have little to no affect on breast surgery and post-operative complications [21, 22]. Finally, our patient selection only contained women who underwent mastectomy for cancer so caution should be used in applying these findings to men and patients who had mastectomy for prophylactic purposes. Our study was consistent with others in that comorbidities such as peripheral vascular disease, and length of hospital stay led to increased risk for 30-day readmission. Since longer length of stay led to more readmissions, we then studied variables that led to longer lengths of stay. Our findings that the occurrence of reconstructive surgery, black race, and certain comorbid conditions were associated with longer lengths of stay were consistent with other studies. Even though many of these factors are non-modifiable, this analysis highlighted the risk factors that increased risk for readmission and length of stay. Our study demonstrated that longer lengths of stay and peripheral vascular disease led to higher risk of readmission. However, we were limited by the inability to assess complications, which undoubtedly are associated with LOS and readmissions. Additional research should be conducted to study the effects of complications on readmissions and LOS for patients undergoing

25 mastectomy. The specific complications that lead to higher readmissions and longer LOS can also be identified. 18 Since readmissions are now associated with quality of care and payers are starting to deny reimbursements for readmissions, it is important to assess variables that may lead to increased rates of readmissions. Our study identified two main risk factors for 30-day readmissions in mastectomy patients. Efforts should be made to optimize patients prior to surgery in attempt to minimize the ill effects from their comorbid conditions. Additional research is needed to determine whether the relationship between readmissions and length of hospital stay is a causative versus associative phenomenon since length of stay is a modifiable factor that may lead to lower readmissions.

26 19 s 1. American Cancer Society. Breast Cancer Facts and Figures McGuire, K.P., et al., Are mastectomies on the rise? A 13-year trend analysis of the selection of mastectomy versus breast conservation therapy in 5865 patients. Ann Surg Oncol, (10): p El-Tamer, M.B., et al., Morbidity and mortality following breast cancer surgery in women: national benchmarks for standards of care. Ann Surg, (5): p United States., et al., Compilation of Patient Protection and Affordable Care Act : as amended through November 1, 2010 including Patient Protection and Affordable Care Act health-related portions of the Health Care and Education Reconciliation Act of , Washington: U.S. Government Printing Office. xxiii, 955 p. 5. Lucas, D.J., et al., Assessing readmission after general, vascular, and thoracic surgery using ACS-NSQIP. Ann Surg, (3): p Schneider, E.B., et al., Patient readmission and mortality after colorectal surgery for colon cancer: impact of length of stay relative to other clinical factors. J Am Coll Surg, (4): p ; discussion Schneider, E.B., et al., Patient readmission and mortality after surgery for hepatopancreato-biliary malignancies. J Am Coll Surg, (5): p Ferrante, J., et al., The use and outcomes of outpatient mastectomy in Florida. Am J Surg, (4): p ; discussion Palit, T.K., D.M. Miltenburg, and F.C. Brunicardi, Cost analysis of breast conservation surgery compared with modified radical mastectomy with and without reconstruction. Am J Surg, (6): p

27 Mortenson, M.M., et al., Immediate breast reconstruction after mastectomy increases wound complications: however, initiation of adjuvant chemotherapy is not delayed. Arch Surg, (9): p Newman, L.A., et al., Meta-analysis of survival in African American and white American patients with breast cancer: ethnicity compared with socioeconomic status. J Clin Oncol, (9): p Crowe, J.P., Jr., et al., Race is a fundamental prognostic indicator for 2325 northeastern Ohio women with infiltrating breast cancer. Breast J, (2): p Jatoi, I., H. Becher, and C.R. Leake, Widening disparity in survival between white and African-American patients with breast carcinoma treated in the U. S. Department of Defense Healthcare system. Cancer, (5): p Dehal, A., A. Abbas, and S. Johna, Comorbidity and outcomes after surgery among women with breast cancer: analysis of nationwide in-patient sample database. Breast Cancer Res Treat, (2): p Collins, T.C., et al., Risk factors for prolonged length of stay after major elective surgery. Ann Surg, (2): p Kassin, M.T., et al., Risk factors for 30-day hospital readmission among general surgery patients. J Am Coll Surg, (3): p Goodney, P.P., et al., Hospital volume, length of stay, and readmission rates in high-risk surgery. Ann Surg, (2): p Kiran, R.P., et al., Outcomes and prediction of hospital readmission after intestinal surgery. J Am Coll Surg, (6): p Kansagara, D., et al., Risk prediction models for hospital readmission: a systematic review. JAMA, (15): p

28 Williams, S., A. Bottle, and P. Aylin, Length of hospital stay and subsequent emergency readmission. BMJ, (7513): p Warren Peled, A., et al., Impact of chemotherapy on postoperative complications after mastectomy and immediate breast reconstruction. Arch Surg, (9): p Decker, M.R., et al., Impact of neoadjuvant chemotherapy on wound complications after breast surgery. Surgery, (3): p