Predictors of Long-Term Survival Among Locally Advanced Non–small Cell Lung Cancer Patients Undergoing Definitive Radiation Therapy

Abstract

Purpose/Objective(s): Lung cancer is the leading cause of cancer death, with a 5 year relative survival of 17.7%. We sought to identify predictors of long-term survival among locally advanced non-small cell lung cancer (LA-NSCLC) patients treated on our institutional prospective trials with dose escalated radiation therapy. Purpose/Objective(s): Patients with LA-NSCLC who underwent definitive radiotherapy between 2004 and 2013 were identified from a prospective multi-institutional database. Penalized Cox proportional hazards modelling with ten-fold cross validation was performed to identify factors predicting for overall survival. Mean lung dose (a/b=3), mean tumor dose (a/b=10), age and age-squared at start of treatment, concurrent chemotherapy, smoking status, sex, KPS, and treated institution were included in our model. The fitted Cox model was used to predict two median survival times per patient, one for each institution, and each patient's institution-specific median survival times were averaged. Characteristics of patients predicted to survive less than and more than 2 years were determined. Results: Of the 114 patients, 92 (81%) had died at the time of data collection. The median survival was 1.8 years (95% CI: 1.3, 2.4). Treating death as a censoring event, the reverse Kaplan-Meier estimated median potential follow-up time was 6.0 years. Younger age, higher KPS, and female gender were strongly associated with improved survival. Among the remaining covariates, higher tumor dose, the use of concurrent chemotherapy, and non-smoking status were associated with decreased risk of death. Dose to the lung had little association with survival. The baseline characteristics for patients stratified by predicted median survival are summarized in Table 1. Although a greater percentage of the long-term survivors were current smokers (50.4%), this resulted from the association between current smoking status and younger age among patients in this cohort. Conclusion: Long-term survivors of LA-NSCLC in our prospective cohort were generally younger, higher-performing, and more likely to be women. Concurrent chemotherapy and higher radiation doses also predicted for improved outcomes.