Apoptosis and BCL-2 expression as predictors of survival in radiation-treated non–small-cell lung cancer

Abstract

Objectives: We assessed the role of apoptosis and the expression of bcl-2, p53, and c-myc oncoproteins in pretreatment histologic specimens as a predictor of response to radiation therapy and survival in non–small-cell lung cancer (NSCLC) patients. Methods: Pretreatment biopsy specimens of 68 patients with NSCLC (62 squamous cell carcinoma, 6 adenocarcinoma) were stained with hematoxylin and eosin. From 5 high-powered fields, the apoptotic index (AI) was calculated as the ratio of apoptotic tumor cells to the total number of tumor cells. Bcl-2, p53, and c-myc oncoprotein expression was detected by immunohistochemical staining. Results: Twenty-nine cases showed partial or complete remission, whereas 39 showed no response. AI ranged from 0.2 to 12.0% (mean ± SD; 4.3 ± 2.6%, median 4.0%). There was no difference in AI between responders (4.0 ± 2.3) and nonresponders (4.5 ± 2.8, p > 0.05). However, in the responders, AI was correlated with the degree of change in tumor volume ( r = 0.41, p < 0.05). In an analysis of 53 subjects who survived more than 1 month after the completion of radiation therapy, the patients with a higher AI ( n = 27, MST = 22.8 m) survived longer than those with a lower AI ( n = 26, MST = 9.2, log–rank, p = 0.03). Patients expressing bcl-2 had poorer survival ( n = 22, MST = 6.0 m) than patients without bcl-2 ( n = 31, 22.8 m, p < 0.003). According to multivariate analysis, three variables, bcl-2 expression, AI, and response to radiation, were independent prognostic factors for survival. Conclusion: A low level of spontaneous apoptosis and expression of apoptosis blocking bcl-2 protein in pretreatment histology predict a poor prognosis for radiation-treated NSCLC patients.