Progression-free survival at 2 years is a reliable surrogate marker for the 5-year survival rate in patients with locally advanced non-small cell lung cancer treated with chemoradiotherapy

Background: In locally advanced Non-Small-Cell Lung Cancer (LA-NSCLC) patients treated with chemoradiotherapy (CRT), optimal surrogate endpoint for cure has not been fully investigated. Methods: The clinical records of LA-NSCLC patients treated with concurrent CRT at Shizuoka Cancer Center between Sep. 2002 and Dec. 2009 were reviewed. The primary outcome of this study was to evaluate the surrogacy of overall response rate (ORR) and progression-free survival (PFS) rate at 3-month intervals (from 9 to 30 months after the initiation of treatment) for the 5-year survival rate. Landmark analyses were performed to assess the association of these outcomes with the 5-year survival rate. Results: One hundred and fifty-nine patients were eligible for this study. The median follow-up time for censored patients was 57 months. The ORR was 72%, median PFS was 12 months, and median survival time was 39 months. Kaplan-Meier curve of progression-free survival and hazard ratio of landmark analysis at each time point suggest that most progression occurred within 2 years. With regard to 5-year survival rate, patients with complete response, or partial response had a rate of 45%. Five-year survival rates of patients who were progression free at each time point (3-months intervals from 9 to 30 months) were 53%, 69%, 75%, 82%, 84%, 89%, 90%, and 90%, respectively. The rate gradually increased in accordance with progression-free interval extended, and finally reached a plateau at 24 months. Conclusions: Progression-free survival at 2 years could be a reliable surrogate marker for the 5-year survival rate in LA-NSCLC patients treated with concurrent CRT.