Is tumor volume reduction during radiotherapy prognostic relevant in patients with stage III non-small cell lung cancer?

Purpose/objective(s) Lung cancer tumor volume reduction is common during radiation treatment (RT). The purpose of this study was to investigate tumor volume reduction ratio (VRR) and its correlation with outcomes in a cohort of patients with stage III non-small cell lung cancer (NSCLC) who underwent image-guided radiochemotherapy (RCTx). Materials/methods Fifty patients with NSCLC treated with fractionated RT at our institution between 2013 and 2017 were included. The relationship between gross tumor volume (GTV) changes during RT (week 1 vs. week 5) and outcomes were evaluated. Results The median radiation dose delivered was 59.4 Gy (median fraction dose, 1.8 Gy). The median GTV before treatment was 119 cm(3), with a median GTV change of - 40%. Patients with more volume reduction had poorer tumor control. A VRR > 40% was associated with a poorer OS and PFS in patients with non-adenocarcinoma (non-ADC) histology. In multivariate analysis, VRR during RT, and chemotherapy (CTx) administration remained related to PFS and OS, while initial GTV remained a significant determinant for OS. In subgroup analyses, and CTx (p = 0.038) affected PFS among non-ADC patients, with initial GTV (p = 0.058) and VRR (p = 0.08) showing non-significant trends. Initial GTV (p = 0.023), VRR (p = 0.038), and CTx (p = 0.01) remained significant predictors for OS in the non-ADC group. Conclusion Worse tumor control and OS in non-ADC patients are observed with more marked RT-induced tumor shrinkage, supporting the development of response-adaptive treatment strategies, particularly in non-ADC NSCLC patients.