The role of thymidylate synthase in non-small cell lung cancer treated with pemetrexed continuation maintenance therapy

Pemetrexed continuation maintenance therapy has been proven to be beneficial for patients with advanced non-squamous non-small cell lung cancer (NSCLC). However, the eligibility criteria for maintenance treatment are too simple. This study sought to evaluate thymidylate synthase (TS) as a predicting biomarker for pemetrexed continuation maintenance treatment in NSCLC. Specimens were collected from 87 patients treated with pemetrexed continuation maintenance therapy before and after four-cycle induction chemotherapy. Real-time quantitative PCR was used to detect TS expression in tissues. The TS expression level was correlated with characteristic clinical data, radiographic response, progression-free time (PFS) and overall survival (OS). Low total TS expression(<8.47) was associated with improved PFS (median: 4.7 months vs. 3.5 months, p = 0.034) and improved OS (time from random assignment: 16.4 months vs. 11.7 months, p = 0.026; time from induction: 19.7 months vs. 14.8 months, p = 0.022). Our results indicate that in NSCLC patients treated with pemetrexed continuation maintenance therapy, low TS expression is associated with improved PFS and OS.