The complex relationship between lung tumor volume and survival in patients with non-small cell lung cancer treated by definitive radiotherapy: a prospective, observational prognostic factor study of the Trans-Tasman Radiation Oncology Group (TROG 99.05).

BACKGROUND AND PURPOSE To investigate the hypothesis that primary tumor volume is prognostic independent of T and N stages in patients with non-small cell lung cancer (NSCLC) treated by definitive radiotherapy. MATERIALS AND METHODS Multicenter prospective observational study. Patient eligibility: pathologically proven stage I-III non-small cell lung cancer planned for definitive radiotherapy (minimum 50 Gy in 20 fractions) using CT-based contouring. Volumes of the primary tumor and enlarged nodes were measured according to a standardized protocol. Survival was adjusted for the effect of T and N stage. RESULTS There were 509 eligible patients. Five-year survival rates for tumor volume grouped by quartiles were, for increasing tumor volume, 22%, 14%, 15% and 21%. Larger primary tumor volume was associated with shorter survival (HR=1.060 (per doubling); 95% CI 1.01-1.12; P=0.029). However, after adjusting for the effects of T and N stage, there was no evidence for an association (HR=1.029, 95% CI, 0.96-1.10, P=0.39). There was evidence, however, that larger primary tumor volume was associated with an increased risk of dying, independently of T and N stage, in the first 18 months but not beyond. CONCLUSIONS In patients treated by non-surgical means we were unable to show that lung tumor volume, overall, provides additional prognostic information beyond the T and N stage (TNM, 6th edition). There is evidence, however, that larger primary tumor volume adversely affects outcome only within the first 18 months. Larger tumor size alone should not by itself exclude patients from curative (chemo)radiotherapy.