Concurrent chemoradiotherapy in locally advanced non-small cell lung cancer: a retrospective analysis of the correlation between radiotherapy-related factors and tumor response

Background: To determine which radiotherapy parameters are associated with the tumor response of locally advanced non-small cell lung cancer (NSCLC) paents undergoing concurrent chemoradiotherapy. Materials and Methods: Thirty one paents with IIIA/IIIB NSCLC underwent chemoradiotherapy with a median dose of 63 Gy. On our actual treatments, we made radiotherapy planning to cover the planning target volume (PTV) with 95% of the prescribed dose, and checked the second CT simulaon when a cumulave dose was about 36 Gy. For this study, each PTV of primary tumor was re-defined with even margins from the gross target volume (GTV), and the actual plan overlaid the re-defined PTV. The correlaons between the tumor response rate during chemoradiotherapy and a2er chemoradiotherapy, and the dose distribuon parameters (D95, V95, mean tumor dose and homogeneity index), total dose and GTV, were evaluated. Results: Median overall survival was 15.5 months and the two-year survival 42.3%. At first recurrence, radiaon-field recurrence, distant metastases and simultaneous recurrence were developed in 35.5%, 41.9% and 9.7% of the cases, respecvely. The dose distribuon parameters were generally favorable and were not related with tumor response rate. The tumor response rate a2er chemoradiotherapy was correlated with the residual GTV at second simulaon (γ=-0.627, p<0.001) and the tumor response rate during chemoradiotherapy (γ=0.541, p=0.003). Conclusion: Minimal correlaon was found between the dose distribuon parameters that were over the minimal dose requirement and tumor response in NSCLC with concurrent chemoradiotherapy. The small residual volume during chemoradiotherapy could indicate good tumor response a2er chemoradiotherapy.