Postoperative survival of non small cell lung cancer

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1 Biological Features and Preoperative Evaluation of Mediastinal Nodal Status in Non Small Cell Lung Cancer Fumihiro Tanaka, MD, Kazuhiro Yanagihara, MD, Yosuke Otake, MD, Mio Li, MD, Ryo Miyahara, MD, Hiromi Wada, MD, and Harumi Ito, MD Department of Thoracic Surgery, Kyoto University, Kyoto, and Department of Radiology, Fukui Medical University, Fukui, Japan Background. To examine whether biological features of primary tumor can help preoperative evaluation of mediastinal nodal status in non-small cell lung cancer. Methods. A total of 450 patients who underwent tumor resection and mediastinal dissection were reviewed. p53 status and proliferative fraction (PI) were evaluated immunohistochemically. Results. The accuracy of preoperative evaluation of mediastinal nodal status with computed tomography (CT) was 72.2%; mediastinal nodal metastases had not been revealed until operation in 59 patients (13.1%) (false-negative), and no metastasis was revealed in 66 patients (14.7%) although mediastinal nodal enlargement had been demonstrated by CT (false-positive). The number of false-negative patients was significantly larger when p53 aberrant expression was positive or when PI was higher. Combined with p53 status and PI, there were 27 false-negatives (24.1%) among patients with aberrant p53 expression and higher PI, whereas only two falsenegatives (1.5%) among those with negative p53 expression and lower PI. Conclusions. Mediastinoscopy may be recommended for tumor showing aberrant p53 expression and higher PI, even when CT demonstrates no mediastinal nodal enlargement. (Ann Thorac Surg 2000;70:1832 8) 2000 by The Society of Thoracic Surgeons Postoperative survival of non small cell lung cancer (NSCLC) remains to be poor [1, 2]. The most important factor to determine the postoperative survival is lymph node metastases (pn factor) as well as distant metastases (pm factor). When metastases to mediastinal lymph nodes are proved pathologically (pn2), 5-year survival rates after surgery have been reported to be around 20% [1 3]. Although postoperative adjuvant therapy has been introduced to improve the survival, the efficacy has not been established [1, 4]. Therefore, induction (or neo-adjuvant) therapy prior to operation has been conducted to improve the survival of pn2 patients, and the efficacy has been demonstrated in prospective randomized studies [5 7]. As a result, when mediastinal lymph nodal metastases are demonstrated preoperatively, induction chemotherapy or chemo-radiotherapy prior to operation is recommended [1]. That is, preoperative evaluation of mediastinal nodal status is important in decision-making of therapy for patients with NSCLC. Computed tomography (CT) is a useful diagnostic modality in evaluation of intrathoracic diseases, and become a routine examination for patients with lung cancer. Recent improvement of postoperative survival of lung cancer patients is apparently caused by accurate Presented at the Poster Session of the Thirty-sixth Annual Meeting of The Society of Thoracic Surgeons, Fort Lauderdale, FL, Jan 31 Feb 2, Address reprint requests to Dr Wada, Department of Thoracic Surgery, Faculty of Medicine, Kyoto University, Shogoin-kawahara-cho 54, Sakyoku, Kyoto, , Japan; wadah@kuhp.kyoto-u.ac.jp. preoperative evaluation and by increased cases of early detection of lung cancer, both of which can be realized by use of CT [1, 3, 8]. That is, CT is useful not only for detection and evaluation of primary tumor (T factor), but also for detection of enlarged lymph nodes. Usually, mediastinal lymph nodes are considered to be abnormal when the short-axis diameter is more than 1.0 cm; subcarinal lymph nodes are sometimes considered abnormal when the short-axis diameter is more than 1.5 cm [9]. However, abnormal, that is enlarged, lymph nodes demonstrated by CT do not always mean metastases to mediastinal lymph nodes, because CT can not distinguish nodal enlargement caused by cancer metastases from non-metastasis nodal enlargement [9]. In addition, cancer metastases are sometimes proved pathologically even in non-enlarged lymph nodes, and nodal metastases can not be revealed until operation in such cases. Therefore, the sensitivity and specificity of CT for detection of mediastinal nodal metastases have been reported to be unsatisfactory [9 11]. Thus, accurate preoperative evaluation of mediastinal nodal status is sometimes difficult, whereas it is critical in decision-making of therapy for lung cancer patients. Recent progress in molecular biology has revealed a variety of biological and genetic disorders involved in development and progress of malignant tumors. Among them, mutations of p53 gene, a tumor suppressor gene, are the most common genetic disorder shown in a variety of malignant tumors including NSCLC [12, 13]. p53 status 2000 by The Society of Thoracic Surgeons /00/$20.00 Published by Elsevier Science Inc PII S (00)

2 Ann Thorac Surg TANAKA ET AL 2000;70: BIOLOGIC FEATURES AND cn STATUS IN NSCLC 1833 has been reported to be clinically important in that abnormal p53 status may serve not only as a significant factor to predict poor prognosis [14] but also as a factor to determine sensitivity to radiation therapy and/or chemotherapy [15]. However, clinical significance of biological features of tumor tissues including p53 status has not been established in NSCLC, and decision-making in therapy for NSCLC patients based on these biological factors is not recommended [16]. The purpose of the article is to examine whether or not biological features including p53 status and proliferative properties of tumor cells can contribute to improvement of accuracy of preoperative mediastinal nodalevaluation. Patients and Methods Patients A total of 450 consecutive patients with pathologic stage (p-stage) IA IV NSCLC who underwent thoracotomy with a complete mediastinal lymph node dissection without any preoperative therapy at the Department of Thoracic Surgery, Kyoto University, from January 1985 through December 1992, were retrospectively reviewed (Table 1). Preoperative clinical staging (c-stage) and postoperative p-stage were reevaluated and determined by the current TNM classification as revised in 1997 [2]. Histologic type and cell differentiation were determined using the classification by the World Health Organization. With regard to tumor differentiation, welldifferentiated squamous cell carcinoma (Sq) and adenocarcinoma (Ad) were both classified as welldifferentiated tumor. Moderately differentiated Sq and Ad were classified as moderately differentiated tumor. Large cell carcinoma (La) as well as poorly differentiated Sq and Ad were classified as poorly differentiated tumor. The other histologic types were excluded in analysis according to cell differentiation. p53 status was determined by immunohistochemical staining (IHS) [16]. Cell proliferation was also evaluated by immunohistochemical detection of proliferating cell nuclear antigen (PCNA) that was expressed in the cell nucleus during late G1 and S stages of cell cycle [17]. All the biologic features were evaluated in histologic sections taken from the primary tumor. For all these patients, the inpatient medical records, chest roentgenogram films, whole-body CT films, bone and gallium scanning data, and operation records were reviewed. CT scans were performed using a CT/T8800 model scanner (General Electrical, Milwaukee, WI) with a 10-mm slice thickness. Mediastinal lymph nodal status was evaluated by a thoracic radiologist (H.I.). Mediastinal lymph nodes were considered to be enlarged when the short-axis diameter was more than 1.0 cm, and subcarinal lymph nodes were considered to be enlarged when the short-axis diameter was more than 1.5 cm. Accuracy, sensitivity, and specificity of CT of mediastinal nodal status were calculated on a per-patient basis. Tissue Preparation and Immunohistochemistry All tumor specimens cut from the primary tumor were immediately fixed in 10% (v/v) formalin, and then embedded in paraffin. Serial 4- m sections were prepared from each sample, and served for routine hematoxylin and eosin staining and IHS to detect aberrant p53 expression and PCNA expression. The procedure for IHS using streptovidin-biotinylated horseradish peroxidase complex method (LSAB kit; Dako Japan, Kyoto, Japan) is described elsewhere [15, 18]. In brief, dewaxed sections were heated in microwave oven for 5 minutes three times each to retrieve their antigeneities. Mouse anti-human p53 monoclonal antibody DO-7 (mouse IgG2b, kappa, 250 g/ml, Dako Japan) diluted at 1:50 and mouse anti-human PCNA, monoclonal antibody PC-10 (mouse IgG2a, kappa, 400 g/ml, Dako Japan) diluted at 1:50 were used as the primary antibody. After incubation with biotinylated sheep anti-mouse IgG antibody, slides were treated with horseradish peroxidase-labeled streptovidin for 10 minutes. As a chromogen, diamino benzidine (Sigma, St. Louis, MO) was used. A total of 1,000 tumor cells were counted for positive staining, and the percentages of positive cells were determined. Fraction of proliferative cells was defined as the percentage of PCNApositive cancer cells (proliferative index, PI). p53 expression was judged to be aberrant when the percentage of cancer cells with nuclear positive staining exceeded 5%. Statistical Methods The numbers of true-positive, false-negative, falsepositive, and true-negative cases for preoperative mediastinal nodal evaluation with CT were defined as TP, FN, FP, and TN, respectively. The sensitivity and specificity were estimated by TP/(TP FN) and TN/(FP TN), respectively. In addition, the positive and negative predictive values were estimated by TP/(TP FN) and TN/(FP TN), respectively. Counts were compared by the 2 test, and trends in counts were analyzed by the 2 test for trends. Continuous data were compared using Student s t test if the distribution of samples was normal, or using the Wilcoxon test if the sample distribution was asymmetric. In addition to univariate analysis, multiple logistic regression models were used to evaluate the covariate-adjusted significance of several factors in determining mediastinal nodal status. A multiple logistic regression analysis was used to determine whether each variable was an independent predictor. Differences were considered significant when the p value was less than All statistical manipulations were performed using the SPSS for Windows software system (SPSS Inc., Chicago, IL). Results p53 Status and PI According to Patients Characteristics Aberrant p53 expression was observed in 201 (44.7%) of the 450 patients. The mean and median PIs for all

3 1834 TANAKA ET AL Ann Thorac Surg BIOLOGIC FEATURES AND cn STATUS IN NSCLC 2000;70: Table 1. Characteristics of Patients and p53 Status, Proliferative Index Characteristic No. of Patients (%) Aberrant p53 Expression: No. of Patients (%) Proliferative Index (PI) Positive Negative p Value Mean SE p Value Total no. of patients 450 (100%) 201 (44.7%) 249 (55.3%) (median: 49.0) Age (mean SD, y) Lower age ( 63 y) 229 (50.9%) 98 (42.8%) 131 (57.2%) Higher age ( 63 y) 221 (49.1%) 103 (46.6%) 118 (53.4%) Gender Male 342 (76.0%) 165 (48.2%) 117 (51.8%) Female 108 (24.0%) 36 (33.3%) 72 (66.7%) Performance status (PS) (83.3%) 171 (45.6%) 204 (54.4%) (15.1%) 26 (38.2%) 42 (61.8%) a a (1.5%) 4 (57.1%) 3 (42.9%) Histology Squamous cell (Sq) 149 (33.1%) 84 (56.4%) 65 (43.6%) Well differentiated 42 (9.3%) Moderately differentiated 75 (16.7%) (Sq versus Ad) (Sq versus Ad) Poorly differentiated 32 (7.1%) Adenocarcinoma (Ad) 250 (55.6%) 94 (37.6%) 156 (62.4%) Well differentiated 98 (21.8%) Moderately differentiated 80 (17.8%) Poorly differentiated 72 (16.0%) Large cell (La) 28 (6.2%) 14 (50.0%) 14 (50.0%) Others 23 (5.1%) Tumor differentiation Well differentiated 146 (32.4%) 50 (34.2%) 96 (65.8%) Moderately differentiated 157 (34.9%) 82 (52.2%) 75 (47.8%) b b Poorly differentiated 147 (32.7%) 69 (46.9%) 78 (53.1%) Clinical stage (c-stage) IA 119 (26.4%) 48 (40.3%) 71 (59.7%) IB 83 (18.4%) 42 (50.6%) 41 (49.4%) IIA 14 (3.1%) 6 (42.9%) 8 (57.1%) IIB 59 (13.1%) 38 (64.4%) 21 (35.6%) T2N1M0 37 (8.2%) T3N0M0 22 (4.9%) IIIA 124 (27.6%) 38 (30.6%) 86 (69.4%) c T3N1M0 14 (3.1%) c T1-3N2M (24.4%) IIIB 31 (6.9%) 17 (54.8%) 14 (45.2%) T4N0-1M0 13 (2.9%) T4N2M0 10 (2.2%) T1-4N3M0 8 (1.8%) IV 20 (4.4%) 12 (60.0%) 8 (40.0%) Pathologic stage (p-stage) IA 111 (24.7%) 41 (36.9%) 70 (63.1%) IB 105 (23.3%) 48 (45.7%) 57 (54.3%) IIA 14 (3.1%) 4 (28.6%) 10 (71.4%) IIB 59 (13.1%) 25 (42.4%) 34 (57.6%) T2N1M0 35 (7.8%) T3N0M0 24 (5.3%) IIIA 84 (18.7%) 42 (50.0%) 42 (50.0%) d d T3N1M0 5 (1.1%) T1-3N2M0 79 (17.5%) IIIB 52 (11.6%) 26 (50.0%) 26 (50.0%) T4N0-1M0 20 (4.5%) T4N2M0 24 (5.3%) T1-4N3M0 8 (1.8%) IV 25 (5.6%) 15 (60.0%) 10 (40.0%) a p value for entire PS. b p value for entire grades of tumor-cell differentiation. c p value for entire c-stages. d p value for entire p-stages.

4 Ann Thorac Surg TANAKA ET AL 2000;70: BIOLOGIC FEATURES AND cn STATUS IN NSCLC 1835 Table 2. Characteristics of Patients and Accuracy of Computed Tomography (CT) for Preoperative Mediastinal Nodal Evaluation Pathological nodal status Preoperative prediction Positive Mediastinal Nodal Metastasis (pn2-3) (cn2-3) (True-Positive) Incorrect (cn0-1) (False-Negative) p Value for Prediction Negative Mediastinal Nodal Metastasis (pn0-1) (cn0-1) (True-Negative) Incorrect (cn2-3) (False-Positive) p Value for Prediction All patients 67 (52.3%) 61 (47.7%) 256 (79.5%) 66 (20.5%) Age Lower age ( 63 y) 42 (60.0%) 28 (40.0%) 129 (81.1%) 30 (18.9%) Higher age ( 63 y) 25 (43.1%) 33 (56.9%) 127 (77.9%) 36 (22.1%) Gender Male 49 (55.1%) 40 (44.9%) 196 (77.5%) 57 (22.5%) Female 18 (46.2%) 21 (53.8%) 60 (87.0%) 9 (13.0%) Performance status (PS) 0 49 (50.5%) 48 (49.5%) 221 (79.5%) 57 (20.5%) 1 16 (61.5%) 10 (38.5%) (78.6%) 9 (21.4%) (40.0%) 3 (60.0%) 2 (100%) 0 (0.0%) Histology Squamous cell (Sq) 17 (44.7%) 21 (55.3%) 81 (73.0%) 30 (27.0%) Adenocarcinoma (Ad) 45 (55.6%) 36 (44.4%) 141 (83.4%) 28 (16.6%) Tumor differentiation Well differentiated 12 (33.3%) 24 (66.7%) 88 (60.3%) 22 (15.1%) Moderately differentiated 29 (55.8%) 23 (44.2%) (52.2%) 23 (14.6%) Poorly differentiated 26 (65.0%) 14 (35.0%) 86 (58.5%) 21 (14.3%) p53 aberrant expression Negative (normal) 46 (73.0%) 17 (27.0%) 142 (76.3%) 44 (23.7%) Positive (aberrant) 21 (32.3%) 44 (67.7%) 114 (83.8%) 22 (16.2%) Proliferative index (PI) Lower ( 49.0%) 35 (64.8%) 19 (35.2%) 123 (72.4%) 47 (27.6%) Higher ( 49.0%) 32 (43.2%) 42 (56.8%) 133 (87.5%) 19 (12.5%) Proliferative index (PI, mean SE) Values are number of patients and percentage of correct and incorrect prediction, based on preoperative nodal status (cn) and pathologic nodal status (pn). patients were 48.1% and 49.0%, respectively. p53 status and PI for each patient group stratified according to patients characteristics are shown in Table 1. Percentage of patients with aberrant p53 expression was significantly lower in well-differentiated tumor (50 of 146 patients, 34.2%) than in moderately (82 of 157 patients, 52.2%) or poorly differentiated tumor (69 of 147 patients, 46.9%). Aberrant p53 expression was seen more frequently in Sq patients (84 of 149 patients, 56.4%) than in Ad patients (94 of 250 patients, 37.6%), which may be related to the fact that ratio of well-differentiated tumor was significantly lower in Sq than in Ad. Aberrant p53 expression was seen more frequently in male patients (165 of 342 patients, 48.2%) than in female patients (36 of 108 patients, 33.3%), which may be related to the fact that ratio of Sq patients was significantly higher in male than in female patients. Increased aberrant p53 expression was seen in higher p-stage patients. PIs were significantly correlated with histologic type, cell differentiation, and tumor progression (p-stage). That is, PIs were significantly higher in Sq than in Ad, lower in well-differentiated tumor than in moderately to poorly differentiated tumor, and higher in higher p-stages. Accuracy of Preoperative Evaluation of Mediastinal Nodal Status In 128 (28.4%) of all 450 patients, mediastinal nodal metastases were proved in histologic sections postoperatively (pn2 to pn3). Mediastinal nodal enlargement had been demonstrated by preoperative CT in 67 patients (true positive, TP), and not in 61 patients (false negative, FN). Among 322 patients with negative mediastinal nodal metastasis (pn0 to pn1), 256 patients had been diagnosed correctly with preoperative CT (true negative, TN), and 66 patients incorrectly (false positive, FP). Therefore, the positive and the negative predictive values in mediastinal nodal metastasis were 52.3% (67/128) and 79.5% (256/322), respectively. The accuracy, sensitivity, and specificity for preoperative evaluation of mediastinal nodal status were 71.8%, 53.2%, and 79.6%, respectively. The accuracy of CT for each patient group stratified according to various patient characteristics and biologic features of the primary tumor is shown in Table 2. In evaluating the role of PI, patients were grouped into lower-pi patients (PI less than 49.0%) and higher-pi patients (PI 49.0% or higher), based on the median PI value. Among all the factors studied, p53 status and PI of

5 1836 TANAKA ET AL Ann Thorac Surg BIOLOGIC FEATURES AND cn STATUS IN NSCLC 2000;70: Fig 1. Biologic features (p53 status, proliferative index) of primary tumor and the accuracy of computed tomography (CT) for preoperative nodal evaluation (per-patient basis). the primary tumor were the most significant factors to affect the accuracy. When aberrant p53 was demonstrated in the primary tumor, 44 (67.7%) of 67 patients with pn2 to pn3 disease were diagnosed incorrectly with preoperative CT and the correct predictive value for positive mediastinal nodal metastasis was only 32.3%; 46 (73.0%) of 63 patients without aberrant p53 expression were diagnosed correctly as having mediastinal enlargement with preoperative CT ( p 0.001). Similarly, there were 42 (56.8%) false-negative results among pn2 to pn3 patients with higher PI, whereas only 19 (35.2%) falsenegative results among pn2 to pn3 patients with lower PI, showing a significantly higher percentage of the incorrect prediction in higher-pi patients ( p 0.020). Moreover, the percentage of patients with false-positive results was significantly lower for higher-pi patients (19 of 152 pn0 to pn1 patients, 12.5%) than for lower-pi patients (47 of 170 pn0 to pn1 patients, 27.6%) ( p 0.001). Although grade of tumor differentiation or histologic type might influence the accuracy of CT evaluation, the influence was weak as compared with p53 status or PI of the tumor. Combined with p53 status and PI, the influence on preoperative nodal evaluation proved to be stronger. As shown in Figure 1, there were only 2 false-negative patients (1.5%) of 135 patients with negative p53 expression and lower PI. In contrast, there were 27 falsenegative patients (24.1%) of 112 patients with aberrant p53 expression and higher PI. In addition, there were only 9 false-negative patients (8.0%) of 112 patients with aberrant p53 expression and higher PI, whereas there were 34 false-negative patients (25.2%) of 134 patients with negative p53 expression and lower PI. Multiple Logistic Regression Analysis To determine whether each patient s characteristic, p53 status, or PI status was an independent predictor of mediastinal nodal involvement (pn2 to pn3), a multiple logistic regression analysis for all patients was performed. Adenocarcinoma, aberrant p53 expression, and higher PI were the strongest independent factors to predict mediastinal nodal involvement; female gender was a marginally significant predictor of mediastinal nodal involvement (Table 3, the left column). Next, a multiple logistic regression analysis for pn2 to pn3 patients was performed to determine an independent factor to correctly predict mediastinal nodal involvement (pn2 to pn3). Aberrant p53 expression and higher PI were most strongly associated with false-negative prediction; poorly differentiated tumor and higher age were also associated with false-negative prediction (Table 3, the middle column). Finally, a multiple logistic regression analysis for pn0 to pn1 patients was performed to determine an independent factor to predict correctly noninvolvement of mediastinal lymph nodes (pn0 to pn1). Aberrant lower PI proved to be most strongly associated with false-positive prediction; non-ad was also associated with false-positive prediction (Table 3, the right column). These results confirmed that aberrant p53 expression and higher PI were significantly associated with the incorrect prediction of mediastinal nodal involvement as well as the presence of mediastinal nodal involvement nodal. Moreover, lower PI proved to be associated with the incorrect prediction of negative mediastinal nodal involvement as well as the absence of mediastinal nodal involvement. Comment Although accurate preoperative evaluation of mediastinal nodal status is important in therapeutic decision making for operable NSCLC, the accuracy obtained has remained unsatisfactory. McLoud and coworkers [19] reported that the sensitivity and specificity of CT for mediastinal nodal status were 64% and 62%, respectively. According to a meta-analysis study on the accuracy of CT, the sensitivity and specificity were 79% and 78%, respectively [10]. The sensitivity (53.2%) demonstrated in the present study seems to be lower than that demonstrated in previous reports, although the specificity

6 Ann Thorac Surg TANAKA ET AL 2000;70: BIOLOGIC FEATURES AND cn STATUS IN NSCLC 1837 Table 3. Multiple Logistic Regression Analysis: Significance of Various Factors in Mediastinal Nodal Metastasis and the Preoperative Evaluation With CT Variable (Measured) Pathological Mediastinal Nodal Metastasis Preoperative Prediction of Positive Mediastinal Metastasis Preoperative Prediction of Negative Mediastinal Metastasis p Value RR (95% CI) p Value RR (95% CI) p Value RR (95% CI) Age (lower/higher) ( ) ( ) ( ) Gender (male/female) ( ) ( ) ( ) Performance status (PS) ( ) ( ) ( ) (0/1/2 3) Histology ( ) ( ) ( ) (nonadenocarcinoma/ adenocarcinoma) Tumor differentiation ( ) ( ) ( ) (poorly/moderately/well) p53 aberrant expression ( ) ( ) ( ) (negative/positive) Proliferative index (PI) (lower/higher) ( ) ( ) ( ) CI confidence interval; RR relative risk. (79.6%) in the present study is comparable. The lower sensitivity may be caused by use of an older CT machine in the present study, and the sensitivity obtained with the current CT machine in our institute is around 75% (unpublished data). In the present study, patients operated on from 1985 through 1992 were analyzed, because preoperative induction therapy conducted after the period may change p53 status and PI values of the primary tumor. In future studies, the sensitivity, specificity, and accuracy will be examined using the present CT machine system, and the conclusions obtained in the present study might be changed. Several biologic features including p53 status and PI have been reported to be a prognostic factor after operation for NSCLC [14, 15, 18]. In addition, p53 status has been reported to predict the efficacy of postoperative adjuvant chemotherapy for NSCLC and to be an important factor in decisions regarding therapy [14]. In the present study, p53 and PI proved to be important factors to predict mediastinal nodal metastases. For patients with tumor showing normal p53 status and lower PI, there was little chance of false-negative CT evaluation for mediastinal nodal metastases (cn0 to cn1/pn2 to pn3). For patients with tumor showing aberrant p53 expression and higher PI, however, there was an increased chance of false-negative evaluation. When biologic features of the primary tumor, that is p53 status and PI, are taken into consideration in combination with CT diagnosis, the accuracy of preoperative mediastinal evaluation may be increased. Thus, a strategy of preoperative mediastinal nodal evaluation and therapy for operable NSCLC may be suggested based on p53 status and PI value. As reported previously, when CT (cn2 to cn3) demonstrates mediastinal nodal enlargement, mediastinoscopy should be performed to examine nodal status pathologically. If mediastinal nodal metastases are pathologically proved by mediastinoscopy, induction therapy before operation should be performed; if not, operation without induction therapy is justified. When mediastinal nodal enlargement is not demonstrated by CT (cn0 to cn1), mediastinoscopy for all patients is questionable. According to a prospective randomized study, mediastinoscopy for all patients has no advantage over CT because of lower cost effectiveness [20]. Therefore, mediastinoscopy is not commonly performed when preoperative CT does not demonstrate mediastinal nodal enlargement. In some cn0 to cn1 cases, however, mediastinal nodal metastases may be revealed postoperatively (cn0 to cn1/pn2 to pn3, false-negative cases). When p53 status and PI of the primary tumor are taken into consideration in selection of candidates for mediastinoscopy, the chance for falsenegative evaluation can be diminished. That is, if mediastinal nodal enlargement is not demonstrated with CT in patients with tumor showing normal p53 status and lower PI, thoracotomy without pathologic examination of mediastinal nodal status by mediastinoscopy can be justified, because there is little chance of finding mediastinal nodal metastases in such cases. However, mediastinoscopy should be performed in patients with tumor showing aberrant p53 and higher PI, even when CT does not demonstrate mediastinal nodal enlargement, because mediastinal nodal metastases that cannot be revealed by CT are sometimes proved pathologically. In the present study, p53 status and PI were examined in a large tumor sample obtained during thoracotomy. However, when biologic features of a tumor are actually taken into consideration in preoperative evaluation, usually only a small specimen can be obtained preoperatively. Because the proliferative nature of each tumor cell is usually heterogeneous, the exact evaluation of PI of the entire tumor can be judged only when a large specimen is examined carefully. In addition, it is known that the cut-off value for the lower and higher PI can be changed depending on the distribution. For these reasons, PI may not be used as a useful marker in preoperative evaluation of nodal status. With respect to p53 status, aberrant p53 can be detected even in a small specimen, when it is warranted that tumor cells are contained in the speci-

7 1838 TANAKA ET AL Ann Thorac Surg BIOLOGIC FEATURES AND cn STATUS IN NSCLC 2000;70: men. However, polymerase chain reaction-based analysis of mutations in p53 gene is a more accurate and sensitive method to determine p53 status. Because the amount of specimen obtained preoperatively for biopsy is usually small and because the tumor cells in the specimen are sometimes morphologically crushed, p53 status determined by polymerase chain reaction-based analysis should be used for preoperative evaluation. Recently, 2-[fluorine 18 fluoro-2-deoxy-d-glucose positron emission tomography (PET) has been proved to be useful in preoperative mediastinal nodal evaluation. In a meta-analysis study on preoperative nodal evaluation, PET proved to be significantly more accurate than CT; the sensitivities and specificities were 79% and 91% for PET and 60% and 77% for CT, respectively [11]. As a preoperative diagnostic modality, PET was not used in the present study and has not been used routinely until now, because PET has not been covered by the healthcare system in Japan. However, because of the superiority of PET over CT, whether or not biologic features including p53 status and PI can improve the accuracy of PET for preoperative mediastinal nodal evaluation should be examined in future. Additional points to study would be whether postoperative recurrence, survival, or cost effectiveness can be improved when these biologic features are introduced and used as clinical markers. We thank Miss Tomoko Yamada for excellent preparation of tumor tissues. We also thank Drs Yozo Kawano, Tatsuo Nakagawa, Tetsuya Takata, Hiroki Oyanagi, and Hiromichi Katakura for technical assistance with this work. References 1. Pearson FG. Non-small cell lung cancer. Role of surgery for stages I III. Chest 1999;116:500s 3s. 2. Mountain CF. Revisions in the international system for staging lung cancer. Chest 1997;111: Tanaka F, Yanagihara K, Ohtake Y, et al. Time trends and survival after surgery for p-stage IIIa, pn2 non-small cell lung cancer (NSCLC). Eur J Cardiothorac Surg 1997;12: Ihde D, Ball D, Arriagada R, et al. Postoperative adjuvant therapy for non-small cell lung cancer: a consensus report. Lung Cancer 1994;11s: Pass HI, Pogrebniak HW, Steinberg SM, et al. Randomized trial of neoadjuvant therapy for lung cancer: intern analysis. Ann Thorac Surg 1992;53: Roth JA, Fossella F, Komaki R, et al. A randomized trial comparing perioperative chemotherapy and surgery with surgery alone in resectable stage IIIA non-small cell lung cancer. J Natl Cancer Inst 1994;86: Rosell R, Gomez-Condina J, Camps C, et al. A randomised trial comparing preoperative chemotherapy plus surgery with surgery alone in patients with non-small cell lung cancer. N Engl J Med 1994;330: Wada H, Tanaka F, Yanagihara K, et al. Time trends and survival after surgery for primary lung cancer during J Thorac Cardiovasc Surg 1996;112: Shields TW. Presentation, diagnosis, and staging of bronchial carcinoma and of the asymptomatic solitary pulmonary nodule. In: Shields TW, ed. General thoracic surgery, 4th ed. Philadelphia: Williams & Wilkins, 1994: Dales RE, Stark RM, Raman S. Computed tomography to stage lung cancer. Approaching a controversy using metaanalysis. Am Rev Respir Dis 1990;14: Ben A, Dwamena MB, Seema S, et al. Metastases from non-small cell lung cancer: mediastinal staging in the 1990s meta-analytic comparison of PFT and CT. Radiology 1999;213: Vogelstein B, Kinzler KW. p53 function, and dysfunction. Cell 1992;70: Greenblatt MS, Bernnett WP, Hollstein M, et al. Mutations in the p53 tumor suppressor gene: clues to cancer etiology and molecular pathogenesis. Cancer Res 1994;54: Mitsudomi T, Oyama T, Kusano T, et al. Mutations of the p53 gene as a predictor of poor prognosis in patients with non-small cell lung cancer. J Natl Cancer Inst 1993;85: Tanaka F, Yanagihara K, Ohtake Y, et al. p53 status predicts the efficacy of postoperative oral administration of tegafur for completely resected non-small cell lung cancer. Jpn J Cancer Res 1999;90: American Society of Clinical Oncology. ASCO special article: clinical practical guidelines for the treatment of unresectable non-small cell lung cancer. J Clin Oncol 1997;15: Bravo R, Frank R, Blundell PA, et al. Cyclin/PCNA is the auxiliary protein of DNA polymerase. Nature 1987;326: Tanaka F, Kawano Y, Li M, et al. Prognostic significance of apoptotic index in completely resected non-small cell lung cancer. J Clin Oncol 1999;17: McLoud TC, Bourgouin PM, Greenberg RW, et al. Bronchogenic carcinoma: analysis of staging in the mediastinum with CT by correlative lymph node mapping and sampling. Radiology 1992;182: Canadian Lung Oncology Group. Investigation for mediastinal disease in patients with apparently operable lung cancer. Ann Thorac Surg 1995;60: