Worse Outcomes for Head and Neck Rhabdomyosarcoma Secondary to Reduced-dose Cyclophosphamide
Menée sur 76 patients pédiatriques atteints d'un rhabdomyosarcome de la tête et du cou traité par chimioradiothérapie entre 2000 et 2018, cette étude monocentrique compare, du point de vue du contrôle local de la maladie et de la survie, l'efficacité d'une radiothérapie photonique et d'une protonthérapie, puis analyse l'association entre la dose de cyclophosphamide administrée et les résultats thérapeutiques
Purpose : Recent trends including the use of proton therapy and administration of reduced-doses of cyclophosphamide have been adapted in head and neck rhabdomyosarcoma (HN-RMS) to reduce late morbidity. Our primary goal was to analyze local control and survival outcomes after photon versus proton irradiation in pediatric patients with HN-RMS, with the secondary goal of analyzing the effect of cyclophosphamide dose on disease outcomes. Methods and Materials : This single-institution cohort study was comprised of 76 pediatric HN-RMS patients treated with definitive chemoradiation from 2000 to 2018. Fifty-one patients (67%) received intensity-modulated photon radiation therapy (IMRT) and 25 (33%) proton therapy. Results : Local failure (LF) at 2 years was 12.5% for parameningeal RMS and 0% for orbital RMS and other head and neck sites (p=0.24). Patients treated with protons were more likely to have received reduced-dose cyclophosphamide (p<0.0001). The 2-year LF was 7.9% in the IMRT cohort versus 14.6% in the proton cohort (p=0.07), with no difference in survival outcomes. Cumulative cyclophosphamide dose was significantly associated with 2-year LF: 0% for cumulative dose of >20g/m2 versus 15.3% for ≤20g/m2 (p=0.04). Among parameningeal RMS patients (n=59), both cumulative cyclophosphamide dose and dose-intensity were associated with local failure (p=0.01). There was a trend toward worse event-free survival for parameningeal RMS patients who received reduced-dose-intensity cyclophosphamide (59.2% versus 70.6%, p=0.11). Conclusions : Both dose-intensity and cumulative cyclophosphamide dose seem to play an important role in achieving local control for HN-RMS patients treated with either protons or photons. Longer follow-up is needed to further assess disease outcomes with proton therapy.