The Impact Of Thoracic Radiation Therapy After Chemotherapy On Survival In Extensive-P Stage Small Cell Lung Cancer: A Propensity Score-Pmatched Analysis

BackgroundThe role of thoracic radiation therapy (TRT) after chemotherapy (CHT) in extensive-stage small cell lung cancer (ES-SCLC) has not been well defined. We investigated whether intensity-modulated radiotherapy (IMRT) improves outcomes in ES-SCLC after CHT compared to CHT alone. MethodsA total of 292 patients who reached a complete response (CR), partial response (PR), or stable disease (SD) after CHT were assigned into groups: CHT + TRT and CHT alone. Propensity score matching was used to balance patient groups (n=72 each). ResultsThe five-year overall survival (OS: 12.3% vs. 3.6%; P<0.001) and progression-free survival (PFS: 3.2% vs. 1.7%; P=0.006) rates were significantly higher in the CHT +TRT group. This data was confirmed in the matched samples (5-year OS: 10.5% vs. 1.6%, P <0.001; PFS: 4.3% vs. 0.0%, P=0.023). The overall (P=0.002) and locoregional (P<0.001) recurrence rates in the CHT +TRT group were significantly lower than in the CHT group. Univariate analysis showed that response evaluation after CHT and TRT were significant prognostic factors of OS. Multivariate analyses revealed that N Stage 0-1 (P=0.02), > 6 cycles of CHT (P=0.042), CR+PR after CHT (P<0.001), and TRT (P <0.001) were independently associated with longer OS compared to CHT alone. ConclusionTRT using IMRT is strongly correlated with improved OS and PFS in ES-SCLC patients reaching CR, PR or SD after CHT. A multicenter, randomized phase III clinical trial is needed to confirm these findings.