Pediatric Cancer

PV QA 3 - Poster Viewing Q&A 3

TU_25_3111 - Proton versus photon radiation therapy for pediatric head and neck rhabdomyosarcoma: disease control, overall survival, and toxicity

Tuesday, October 23
1:00 PM - 2:30 PM
Location: Innovation Hub, Exhibit Hall 3

Proton versus photon radiation therapy for pediatric head and neck rhabdomyosarcoma: disease control, overall survival, and toxicity
D. L. Casey, L. Wexler, and S. L. Wolden; Memorial Sloan Kettering Cancer Center, New York, NY

Purpose/Objective(s): Head and neck rhabdomyosarcoma (HNRMS) is a uniquely challenging site given the critical anatomy of this region and the concern for late effects in these young patients. Proton therapy provides promise in sparing late effects without a compromise in clinical outcomes. We compared disease control, overall survival, and acute toxicity after photon versus proton irradiation in pediatric patients with HNRMS.

Materials/Methods: This was a single-institution cohort study comprised of 66 pediatric patients (age 1-25) treated with definitive chemoradiation for HNRMS from 2000 to 2017. Fifty-one patients (77%) were treated with intensity modulated radiation therapy (IMRT) and 15 patients (23%) were treated with proton therapy. Locoregional control, event-free survival (EFS), overall survival (OS), and acute toxicity were compared among the 2 groups.

Results: Median follow up of surviving patients was 9.8 years in the IMRT cohort versus 1.6 years in the proton cohort. Median age at the time of radiation was 8.1 years in the IMRT cohort versus 7.9 years in the proton cohort. The two cohorts were similar with respect to gender, race, tumor site (parameningeal, orbital, or other head and neck), tumor size, stage and group. However, patients treated with IMRT were more likely to be PAX/FOXO1 fusion-positive (19% versus 0%, p=0.06) and were more likely to have nodal involvement at diagnosis (51% versus 20%, p=0.03). Locoregional control at 5 years was 91% in the IMRT cohort versus 85% in the proton cohort (p=0.28). All local failures were in-field; there were no marginal failures in either cohort. EFS and OS at 5 years were 71% and 75% in the IMRT cohort versus 74% and 71% in the proton cohort (p=.97 and p=.54, respectively). There were no grade 4 acute toxicities in either cohort. Grade 3 mucositis rates were slightly higher in the IMRT cohort (20% versus 13%, p=0.58), while grade 3 dermatitis rates were higher in the proton cohort (33% versus 2%, p<0.0001).

Conclusion: Photon and proton therapy appear to result in similar locoregional disease control and survival in children with HNRMS. However, longer follow up is needed in the proton cohort prior to fully establishing their equivalence in terms of disease outcomes. Given the potential of proton therapy to spare late morbidity while maintaining excellent clinical outcomes, we recommend treatment of pediatric HNRMS with proton therapy whenever feasible.

Author Disclosure: D.L. Casey: None. L. Wexler: None. S.L. Wolden: None.

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