Background: Distinguishing a metachronous lung cancer from a metastatic or recurrent lesion in patients with a prior history of non-small cell lung cancer is a challenging task. Previous studies have suggested histologic type and disease-free interval as criteria for diagnosing metachronous lung cancer. These factors may not be as relevant now that current imaging allows for earlier detection of tumors and with the rising incidence of adenocarcinoma. The purpose of this study was to reexamine the factors that determine outcomes in patients with a second primary lung cancer.
Methods: A retrospective review of a prospective lung cancer database was performed to identify patients with metachronous lung cancer. Metachronous lung cancer was defined as any non-small cell lung cancer occurring after a prior resection regardless of disease-free interval or histologic type. The Kaplan-Meier method was used for survival analysis. The Mantel-Cox method was used to compare overall survival. Cox regression was used for multivariate analysis.
Results: Fifty-eight patients had metachronous lung cancer. Overall survival at 5 years was 66% (stage IA, 74%; IB, 59%; all other stages, 0%; p = 0.01). Seventy-two percent (42 of 58 patients) had similar histologic type. There was no difference in overall survival based on similar versus different histologic type (65% versus 73%; p = 0.77). Median disease-free interval was 42 months (range, 8 to 312 months). Disease-free interval was not a significant predictor of overall survival (p = 0.24). The extent of resection included wedge (36%, 21 of 58 patients), segmentectomy (24%, 14 of 58 patients), and lobectomy (40%, 23 of 58 patients), with no difference in overall survival (58% versus 60% versus 75%, respectively; p = 0.32).
Conclusions: These data suggest that early tumor stage is the only significant determinant of survival after surgical treatment of metachronous lung cancer. Neither histologic type nor disease-free interval was of prognostic value. Limited resections may be adequate treatment.