Assessing the impact of proton versus photon therapy on health-related quality of life in lung cancer

Background and purpose: A more conformal dose deposition of intensity-modulated proton therapy (IMPT) may enhance health-related quality of life (HRQoL) through reduced radiation-induced toxicities, versus photonbased intensity-modulated radiotherapy (IMRT). However, most patients are selected for IMPT based on relative reduction in mean heart dose and correlated 2-year mortality. A HRQoL difference would thus not necessarily be expected. This study evaluates HRQoL outcomes in patients with lung cancer treated with IMPT versus IMRT. Materials and methods: Patients considered for IMPT via the model-based approach and treated with IMPT or IMRT were included. HRQoL was measured using EQ-5D-5 L, EQ-VAS, and EORTC QLQ-C30 Global Health Status (GHS) at baseline, 3, 6, 12 months, and annually up to 5 years. Generalised linear mixed effects (GLM) models were developed in R to assess the impact of radiation modality on HRQoL. Missing data were handled using multiple imputation with propensity score weighting to balance treatment groups. Radiation modality, WHO performance status, baseline HRQoL, and baseline dyspnoea were included as fixed effects in final models. Minimal important difference cut-offs were 0.03 (EQ-5D-5 L), and 0.05 (EQ-VAS; GHS). Results: 171 IMPT and 71 IMRT patients were included (mean follow-up: 8 months). Disease was predominantly stage III non-small cell lung cancer and most patients received chemotherapy. Baseline mean HRQoL scores were similar between groups. Coefficient estimates for IMPT versus IMRT were -0.022 (EQ-5D-5 L), -0.008 (EQ-VAS) and -0.014 (GHS). Differences were not deemed statistically significant nor clinically relevant. Conclusion: Certain clinical advantages for IMPT have previously been demonstrated, but no significant difference in HRQoL between IMPT and IMRT was observed.