Regional Nodal Control for Head and Neck Alveolar Rhabdomyosarcoma

To assess clinical outcomes and patterns of failure, particularly regional nodal control, for pediatric patients treated with proton beam therapy (PBT) for head and neck alveolar rhabdomyosarcoma (HN-ARMS).

Between 2006 and 2015, 14 patients with HN-ARMS were enrolled in a prospective registry protocol and treated with PBT at a single institution. Of the patients, 8 (57%) presented with localized disease and 6 (43%) with regional nodal metastases. All patients were treated with systemic therapy per accepted cooperative group regimens. All patients received PBT to the primary site and involved nodal disease with a median dose of 50.4 Gy (relative biological effectiveness). Elective nodal irradiation was not delivered.

The median follow-up period for surviving patients was 4.3 years. The 5-year overall survival and disease-free survival rates for the cohort (N = 14) were 45% and 25%, respectively. There were 10 relapses in the cohort: 7 regional nodal, 1 combination local and regional nodal, and 2 leptomeningeal. In 6 of 8 patients (75%) with no nodal disease at diagnosis, isolated regional nodal relapse developed. All nodal relapses occurred in first-echelon draining lymph node basins relative to the primary tumor site. Of 6 patients who presented with nodal metastases, 2 had regional nodal relapse; both of these nodal relapses occurred in the same nodal basin that was initially involved by disease but was not completely targeted as part of the primary treatment plan.

High rates of regional nodal relapse are observed for HN-ARMS patients, including patients with no nodal disease at diagnosis. These data suggest that HN-ARMS patients may benefit from elective nodal irradiation to treat at-risk draining lymph node stations relative to the primary tumor site. We further recommend coverage of the entire nodal level for any sites of initial nodal disease at diagnosis, given the high risk of failure at these sites.