Background: To estimate the effectiveness of expression of the tumor proliferative marker Ki-67 antigen (Ki-67) as a postoperative prognostic marker, the authors analyzed Ki-67 expression and its correlation with postoperative survival and other clinicopathologic factors, including preoperative smoking habits, in patients with resected nonsmall cell lung carcinoma (NSCLC).
Methods: A total of 156 patients with resected NSCLC at the study institution were investigated. Postoperative survival rates were estimated based on demographic and clinicopathologic factors, including Ki-67 expression and preoperative tobacco smoking habits.
Results: The overall postoperative 5-year survival rate in patients with high Ki-67 labeling indices (>/= 20%) was 39.6% compared with 67.7% in patients with low Ki-67 labeling indices. This finding was significant for all resected cases and for each pathologic disease stage (P < 0.05). The postoperative 5-year survival rate in patients with a history of heavy smoking (>/= 30 pack-years) was 47.6% compared with 62.5% for other patients (P = 0.027). This result was especially significant in patients with International Union Against Cancer Stage I disease and in patients with nonsquamous cell carcinoma (P < 0.03). The authors also observed a positive correlation between the Ki-67 labeling index and preoperative smoking habits (P = 0.0002). Multivariate analysis demonstrated that lymph node involvement, tumor differentiation, and Ki-67 labeling index were significant prognostic factors in NSCLC (P < 0.01).
Conclusions: Tumor Ki-67 expression is a strong prognostic factor in NSCLC, especially adenocarcinoma. It may be hypothesized that tobacco mutagenicity may play a role in the growth and extension of NSCLC, which is one of the major impediments to postoperative survival in patients with a history of heavy smoking.