Reduction of tumor volume during radiotherapy in patients with small-cell lung cancer and its prognostic significance

Background Several studies have reported the potential prognostic significance of tumor volume reduction ratio (VRR) induced by radiotherapy (RT) in patients with non-small-cell lung cancer. However, there are no data yet on the prognostic significance of volumetric shrinkage in patients with small-cell lung cancer (SCLC). This study aimed to demonstrate the correlation between tumor volume reduction ratio and treatment outcomes. Materials and methods The study included 61 patients with SCLC treated with fractionated RT of the primary tumor at our institution between 2013 and 2020. The relationship between volumetric changes in gross tumor volume (GTV) during radiotherapy and outcomes were analyzed and reported. Results The median radiation dose was 59.4 Gy (median fraction dose was 1.8 Gy). The median GTV before radiotherapy was 74 cm 3 , with a median GTV reduction of 48%. There was a higher VRR in patients receiving concurrent radiochemotherapy ( p = 0.05). No volumetric parameters were identified as relevant predictors of outcome in the entire cohort. In multivariate analysis, only age had an impact on survival, while prophylactic whole-brain radiation influenced the progression-free survival significantly. Conclusion Concurrent chemotherapy was associated with a higher VRR than sequential chemotherapy. No significant impact of VRR on patients’ outcome or survival was detected.