Ann Thorac Surg 2006;82:1180-1184
© 2006 The Society of Thoracic Surgeons
Original Articles: General Thoracic
Surgical Results in T2N0M0 Nonsmall Cell Lung Cancer Patients With Large Tumors 5 cm or Greater in Diameter: What Regulates Outcome?
Yasuhiko Ohta, MD*,
Ryuichi Waseda, MD,
Hiroshi Minato, MD,
Naoki Endo, MD,
Yosuke Shimizu, MD,
Isao Matsumoto, MD,
Go Watanabe, MD
Department of General and Cardiothoracic Surgery and Pathology, Kanazawa University School of Medicine, Kanazawa, Japan
Accepted for publication April 7, 2006.
* Address correspondence to Dr Ohta, Department of General and Cardiothoracic Surgery, Kanazawa University School of Medicine, Takara-machi 13-1, Kanazawa 920-8641, Japan (Email: yohta{at}med.kanazawa-u.ac.jp).
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Abstract
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BACKGROUND: We assessed the surgical results along with the clinical and biological features of nonsmall-cell lung cancer (NSCLC) patients with localized large tumors.
METHODS: The study population consisted of 86 NSCLC patients who underwent complete resection of tumors 5 cm or larger in diameter in stage IB (T2N0M0). We immunohistochemically assessed the expression of angiostatin and endostatin.
RESULTS: The median tumor size was 6.0 cm (range, 5 to 14 cm). The operative procedures used were lobectomy in 71 cases, bilobectomy in 8 cases, and pneumonectomy in 11 cases. Fifty patients (58.1%) relapsed during the mean follow-up period of 33.6 ± 4.5 months. The median disease-free interval was 9 months. Of 44 recurrent patients whose disease-free interval could be identified, 25 patients (56.8%) relapsed within 12 months after the operation. The overall 5- and 10-year survival rates were 42.0% and 24.2%, respectively. Multivariate analysis showed that the degree of pleural involvement and angiostatin expression within the tumor were independent prognostic indicators. The endostatin expression within tumors also had a weaker relationship with outcome.
CONCLUSIONS: Long-term surgical results were poor and early relapse was common in this cohort. In addition to pleural involvement, the tumor-induced expression of angiostatin and endostatin merit further investigation to gain possible insights into selection of patients who will benefit from surgery as the first line treatment.
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Introduction
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Surgery remains the mainstay treatment for localized nonsmall-cell lung cancer (NSCLC) patients irrespective of the tumor size. As tumor size is crucial for the oncological outcome in NSCLC patients, the effects of surgical treatment are still uncertain in patients with large tumors. Although lung cancer is considered a surgically treatable disease in the relatively early stages, recent retrospective clinical assessment showed that a diameter of more than 5 cm is the threshold predicting poor prognosis in lung carcinoma, suggesting that the current staging system should be revised [1–4]. On the other hand, some investigators suggested that localized large tumors also include those with less metastatic potential [5]. However, the biological features specific to large tumors have not been clarified.
There have been a number of studies using the experimental metastasis paradigm in the areas of both basic and clinical research. Based on such studies, it has begun to become clear that the removal of the primary tumor occasionally results in stimulation of cancer cell proliferation in metastatic foci [6–9]. Interestingly, the inhibition of proliferation of these metastatic foci can be explained partly by the production of antiangiogenic factors, such as angiostatin and endostatin [10, 11]. These factors are both endogenous angiogenesis inhibitors, which are related to the inhibition of metastatic growth by the primary neoplasms. From this specific oncologic viewpoint, the appropriateness of removal of the primary tumor as the first line of treatment remains an open question, especially in patients with large primary tumors. On a hypothesis that large tumors have a high risk of systemic micrometastasis and produce inhibitory antiangiogenic factors, we performed the present retrospective review to assess surgical results by highlighting angiostatin and endostatin expression in NSCLC patients with large tumors in the relatively early stage of disease.
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Patients and Methods
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Patients
From January 1981 to December 2004, a total of 1,436 NSCLC patients underwent pulmonary resection at Kanazawa University Hospital. Of these patients, 283 (19.7%) had bulky primary tumors 5 cm or larger in diameter, and complete resection of the primary tumor could be achieved in 259 patients. Among these 259 patients, 86 patients (72 men and 14 women) with pathologic stage IB tumors (T2N0M0) according to the TNM classification [12] who had undergone complete resection with systematic lymphadenectomy were included in this retrospective review. Lymph node biopsy through mediastinoscopy or thoracoscopy was performed selectively in 19 patients with clinical N2 diagnosis based on the results of computed tomography and 201Tl or 18F-fluorodeoxyglucose (FDG) positron emission tomography scan. None of the patients underwent any preoperative induction treatment. The degree of pleural involvement was classified pathologically as follows: p0, no invasion; p1, tumor invasion reached the visceral pleura but not beyond; p2, tumor invasion penetrated the visceral pleura but not the parietal pleura. In this study, N1 nodal station number was designated according to the map by Naruke and colleagues [13]. Written informed consent was obtained from all patients.
Immunohistochemical Assessment of Angiostatin, Endostatin, and Vascular Endothelial Growth Factor-A
Resected tumor specimens could be collected from 83 patients. After reviewing the hematoxylin and eosin–stained slides of the tumor specimens, we selected blocks of the invasive edge in the tumor area. Paraffin-embedded tumor tissues were cut into consecutive sections 4 µm thick, deparaffinized, and subjected to immunohistochemical staining using the labeled streptavidin-biotin method, as described previously [14]. The primary antibodies used in the present study were a rabbit polyclonal antibody to angiostatin (Oncogene Research Products, Cambridge, Massachusetts) diluted 150-fold [15], a rabbit polyclonal antibody to endostatin (Lab Vision, Fremont, California), and a rabbit polyclonal antibody to vascular endothelial growth factor (VEGF [Santa Cruz Biotechnology, Santa Cruz, California]) diluted 100-fold. Negative controls were stained using all reagents except the primary antibodies. As positive controls for angiostatin and endostatin, we used formalin-fixed, paraffin-embedded human melanoma and tonsil tissues, respectively, according to the manufacturers' recommendations.
The immunoreactivities were graded as (–), (+), and (++) according to the intensity of the tumor cells: (–) represents positive staining of 0% to 10% of the total area, (+) represents 10% to 50% positive staining, and (++) represents the strongest staining of more than 50% at x200 magnification. For assessment of angiostatin and endostatin expression, tumors with (–) staining were classified as negative. For assessment of VEGF-A expression, tumors with the strongest staining were defined as overexpressing VEGF-A [14]. The positivity of these markers was evaluated by two independent viewers without knowledge of the clinical factors.
Statistical Analysis
Survival time was measured from the date of surgery. The disease-free interval was calculated for patients who showed relapse and was defined as the interval between time of lung surgery and clinical or radiographic demonstration of the first recurrence. Survival curves were plotted by the Kaplan-Meier method, and univariate comparisons were performed by the log-rank test. Zero time was the date of surgical treatment. The effects of age, sex, pathology type (squamous versus other), location of primary tumor (right versus left and upper lobe versus lower lobe), nodal status (N0 versus N1), pleural involvement (p0/1 versus p2), adjuvant systemic chemotherapy, VEGF-A, angiostatin, and endostatin on overall survival and disease-free interval were assessed. Age and tumor size were classified as being in the high or low group relative to the median value. For multivariate analysis, Cox's proportional hazards regression was used and factors with p less than 0.10 were included in the final model. Associations between variables were analyzed with the 
2 test. The Mann-Whitney U test for differences in mean values was used for comparison of nominal data. Mean values are shown ± SE.
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Results
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The basic clinical and pathologic features of the patients are shown in Table 1. The patients ranged in age from 45 to 84 years (median age, 69.0). The median tumor size was 6.0 cm (range, 5 to 14 cm). The pathological types were as follows: 50 squamous cell carcinomas, 31 adenocarcinomas, 3 adenosquamous cell carcinomas, and 2 large cell carcinomas. The operative procedures used were lobectomy in 71 cases, pneumonectomy in 7 cases, and bilobectomy in 8 cases. Postoperative adjuvant chemotherapy was performed in 24 patients. In-hospital mortality for all 86 patients was 0.01% (1 of 86). Information about overall survival and disease-free interval could be obtained for all patients and for 44 patients, respectively. In the mean follow-up period of 33.6 ± 4.5 months (range, 1 to 146), 50 patients (58.1%) relapsed. Of the 44 recurrent patients whose disease-free interval could be identified, 25 (56.8%) relapsed within 12 months after surgical removal of the primary tumors. The median disease-free interval was 9 months (range, 2 to 105). Among the 22 patients whose recurrent pattern could be identified clearly, distant and local recurrence developed in 19 and 3 cases, respectively. In the total cohort, the overall 5- and 10-year survival rates were 42.0% and 24.2%, respectively. The disease-free survival rate at 5 years was only 10.3%. With respect to the pleural involvement, the patients with p2 showed significantly poorer survival and shorter period of disease-free interval as compared with patients with p0–1 (Fig 1).
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Fig 1. Kaplan-Meier overall survival plots for 120 T2N0-1M0 nonsmall cell lung cancer patients with large tumors 5 cm or greater in diameter stratified by pleural involvement. The degree of pleural involvement was classified pathologically as follows: p0, no invasion; p1, tumor invasion reached the visceral pleura but not beyond; p2, tumor invasion penetrate the visceral pleura but not the parietal pleura. The patients with p2 (bottom straight line) showed significantly poorer survival compared with patients with p0–1 (top straight line; p = 0.008). The survival curves are combined with dashed lines representing the 90% confidence interval.
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Vascular endothelial growth factor-A, angiostatin, and endostatin antigens were identified mainly in the cytoplasm of tumor cells (Fig 2). These antigens were also identified in vascular endothelial cells, and angiostatin antigen was also found in some smooth muscle cells and lymphatic cells.
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Fig 2. Examples of immunohistochemical staining for (A) angiostatin and (B) endostatin. Cytoplasmic staining was positive in tumor cells. (Original magnification, x400.)
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The percentage of patients with VEGF-A overexpression was 75.9% (63 of 83 patients). Four cases were classified as (–) and 16 cases were classified as (+). On the other hand, the percentages of patients positive for angiostatin and endostatin expression were 13.3% (11 of 83 patients) and 54.2% (45 of 83 patients), respectively.
In univariate analysis, pleural involvement (p2), negativity for angiostatin, and negativity for endostatin had significant negative impact on overall survival (Table 2). While the overall 5- and 10-year survival rates of angiostatin-positive or endostatin-positive patients were 47.0% and 29.1%, respectively, those of angiostatin-negative and endostatin-negative patients were 21.6% and 0%, respectively (p = 0.0049; Fig 3). Although the number of patients was limited (n = 7), the 10-year survival rate of angiostatin-positive and endostatin-positive patients was 83.3%. Multivariate analysis showed that pleural involvement and angiostatin were independent prognostic indicators on overall survival (Table 3).
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Fig 3. Kaplan-Meier overall survival plots of T2N0M0 nonsmall-cell lung cancer patients with large tumors 5 cm or greater in diameter stratified by the expression of angiostatin and endostatin. The difference was statistically significant (p = 0.0049). The survival curves are combined with dashed lines representing the 90% confidence interval. Angiostatin (+) or endostatin (+) (n = 50; top straight line); angiostatin (–) or endostatin (–) (n = 33; bottom straight line).
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Comment
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Currently, surgical resection represents the standard first line of treatment for localized NSCLC in the early stages irrespective of tumor size. However, earlier studies indicated that the surgical outcome of NSCLC with large tumors more than 5 cm in diameter is poor. Carbone and associates [2] reported that 5-year survival rate of 111 NSCLC patients with T2 tumors more than 5 cm in diameter was 35.1%. In their series, the significant survival difference based on this threshold remained in N0 and N2-3 status. In the assessment of 60 pN0-NSCLC patients with a tumor size greater than 5 cm, Takeda and coworkers [4] reported that 5-year survival rate after surgery was 46.6%. Cangir and associates [3] also found that the 5-year survival rate of patients with tumors larger than 5 cm in diameter was significantly poorer than that of patients with tumors measuring 3.1 to 5 cm in diameter when patients at various stages were included. In our series highlighting localized pT2N0M0 patients with a tumor size of 5 cm or larger in diameter, we similarly found poor outcomes, with a 5-year survival rate of 42.0%. Consistent with previous data, the surgical results of patients with large tumors 5 cm or greater in diameter were poor after the initial operation even for those at the earliest stage.
Although it is still not clear which population among these patients with localized NSCLC with large tumors would benefit from surgery, the findings of the present study have some implications for the selection of patients that may benefit from surgical resection. Considering the possibility that the lack of tumor-induced growth inhibitory factors may accelerate residual micrometastatic foci after removal of the primary site, we performed immunohistochemical assessment of the expression of two noble markers, angiostatin and endostatin. These two biological markers appeared to be associated with surgical outcomes in the present study. Angiostatin is a proteolytic fragment of plasminogen, which was found originally in a primary Lewis lung carcinoma [10].
There has been only one previous report of immunohistochemical determination of angiostatin expression in lung cancer, in which the results obtained in 143 NSCLC patients in stage I to IIIA indicated that angiostatin expression within the tumor is a favorable prognostic factor [15]. Our observations regarding the relationship between angiostatin expression and patients outcome were consistent with the findings of this previous study. Further, while the percentages of patients with tumors positive for angiostatin were 24% (34 of 143) among the total patient population in various stages and 24% (11 of 45) among patients in stage I and II in this previous study, the percentage of patients positive for angiostatin expression was only 13.3% (11 of 83) in our series using the same antibody under the same experimental conditions. Therefore, the expression of angiostatin within the tumor may be suppressed in large lung cancer lesions.
Conversely, endostatin was isolated originally from murine hemangioendothelioma [11] and identified as the C-terminal fragment of its precursor, collagen XVIII [16]. With regard to endostatin expression in lung cancer, the presence of its precursor, collagen XVIII, in lung cancer cells was confirmed previously [17]. Notably, some investigators from the same institute reported previously that its expression in lung cancer tissue was associated with tumor progression and poor outcomes in assessment of patients at various stages [17, 18]. The endostatin expression in tumor tissue was also reported to be associated with tumor grade and poor outcome in other neoplasms [19]. Interestingly, in hepatocellular carcinoma, collagen XVIII expression decreases with both increasing tumor size and tumor progression [20].
Considering these conflicting phenomena, the relationship between endostatin expression within the tumor and patient outcome may be altered according to the tumor type and their phase or stage of progression. The presence or absence of micrometastases will also inevitably affect this relationship. In the present study, we found that both of these antiangiogenic factors were actually expressed in some tumors. In our series of large tumors 5 cm or more in diameter, although the percentage of tumors positive for endostatin expression was relatively high as compared with that of tumors positive for angiostatin expression, both endostatin and angiostatin expression at the primary site were associated with preferable outcome on overall survival. Therefore, it is unlikely that loss of tumor-induced angiostatin/endostatin expression at the primary site after removal of the tumor affects early relapse. Our findings support the idea that the presence of these antiangiogenic factors within the tumor is associated with preferable outcome after removal of the primary tumor as the first line of treatment.
We also found that the degree of pleural invasion was associated with surgical results, consistent with previous findings reported by Carbone and colleagues [2]. The appropriateness of initial operation in patients with pleural invasion must be determined carefully in patients with the disease.
In conclusion, long-term surgical results were not satisfactory, and the frequency of early relapse was high in this cohort. Pleural involvement was determined as a significant independent prognostic indicator of overall survival. Further, angiostatin/endostatin expression within tumors should be investigated to gain possible insights into the selection of patients who will benefit from surgery as the first line of treatment.
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Abstract
Introduction
