PURPOSE: To develop a prediction model for patients undergoing surgery for stage IA, IB Nonsmall cell lung cancer (NSCLC). The hypothesis was that mortality can be more effectively predicted by integrating size and histology rather than relying solely on conventional staging.
METHODS: We used the SEER database. Inclusion criteria were: 1) primary NSCLC, 2) potentially curative surgery (wedge resection, segmentectomy, lobectomy, bilobectomy, pneumonectomy) 3) surgical stage IA or IB, and 4) lymph node dissections done. Exclusion criteria were: 1) second primaries 2) lung cancer other than NSCLC. Primary outcome was time to death. Cox proportional hazards and Kaplan-Meier methods were used, model comparisons were done using the -2log-likelihood.
RESULTS: From 1998-2000, 8,563 patients were included. Multivariate Cox analysis demonstrated that size (HR 1.315 (95% CI 1.266-1.366), p<0.0001) and adenocarcinoma (HR 1.088 (95% CI 1.013-1.170), p=0.0212) were associated with all-cause mortality. The proportional hazard from larger tumors attenuated with time (Interaction size x time (months) HR 0.997 (95% CI 0.996-0.998), p<0.0001). Multivariate Cox analysis demonstrated that size (HR 1.465 (95% CI 1.381-1.554), p<0.0001; interaction size x time HR 0.995 (95% CI 0.994-0.997), p<0.0001) was also associated with death due to cancer. The proportional hazard of death due to cancer for those with adenocarcinoma, however, increased with time from surgery (interaction adenocarcinoma histology x time HR 1.008 (95% CI 1.005-1.012), p<0.0001), indicating that late recurrences of adenocarcinoma were more common than with other forms of NSCLC. Specifying the size of the tumor in centimeters (p<0.0001) and adding tumor histology (p=0.021) improved model performance compared to the TNM system. The greatest discordance between the complete model and the TNM prediction were in those patients with adenocarcinomas 2-3 cm in size (TNM overestimates survival) and those with squamous cell carcinoma 3-4 cm in size (TNM underestimates survival).
CONCLUSION: Staging based on more precise size and histology assessment is superior to the TNM classification.
CLINICAL IMPLICATIONS: Late recurrences of adenocarcinoma are more common, and this may impact on decisions regarding adjuvant chemotherapy following surgery.
DISCLOSURE: David Ost, None.