Comparison of radiation-induced temporal lobe injury after helical tomotherapy versus conventional intensity-modulated radiotherapy for nasopharyngeal carcinoma: a propensity score-matched cohort study

PURPOSE: To compare the incidence of radiation-induced temporal lobe injury (TLI) between helical tomotherapy (HT) and conventional intensity-modulated radiotherapy (IMRT) in patients with nasopharyngeal carcinoma (NPC). METHODS: We retrospectively reviewed the medical records of NPC patients who underwent curative-intent HT or IMRT from March 2015 to December 2020 at our institution. Propensity score matching (1:1) was performed to minimize the impact of potential confounders. TLI was diagnosed based on the magnetic resonance imaging (MRI) findings. The actuarial rates of TLI were analysed by the Kaplan-Meier method and log-rank test. Univariate and multivariate analyses were used to determine prognostic factors for TLI. RESULTS: 837 patients were included, of which 422 were treated with IMRT and 415 with HT. After matching, 286 patients in each group were successfully matched. The median follow-up time was 47.57 months (IQR, 37.06–58.81 months) and 46.28 months (IQR, 37.14–57.02 months) for the IMRT and HT groups, respectively. The crude incidence of TLI was 19.2% and 11.2% (P = 0.010), and the 5-year actuarial rate of TLI was 31.7% and 18.1% for the IMRT and HT groups (P = 0.011), respectively. Multivariate analysis showed that radiotherapy technique, age, sex, T stage, GTV, Dmax, D2cc, D1cc, D0.5 cc, V60 and V65 of bilateral temporal lobes (TL) were independent predictors for TLI (all P < 0.05). CONCLUSION: Reduced irradiated TL volumes and doses of HT consequently reduced incidence and severity of TLI compared to IMRT. In addition, Dmax, D2cc, D1cc, D0.5 cc, V60, and V65 of TL contributed to the TLI. CLINICAL TRIAL NUMBER: Not applicable.