Adult Head and Neck Rhabdomyosarcoma: Management, Outcomes, and the Effect of Intensity Modulated Radiation Therapy on Locoregional Control

PURPOSE: Only 9% of adult rhabdomyosarcomas (RMS) present with primary disease in the head and neck (HNRMS). Management is often extrapolated from the pediatric experience in which prognosis is better but treatment imperatives differ. We report management and outcomes of adult HNRMS treated over 3 decades. METHODS AND MATERIALS: Adult HNRMS treated from 1984 to 2017 were reviewed. HNRMS were categorized as embryonal/alveolar (E/A) or pleomorphic (P). Standard management was as follows: E/A-HNRMS were treated with neoadjuvant chemotherapy, definitive chemoradiotherapy (CRT), and then maintenance chemotherapy. P-HNRMS were generally treated with surgery +/– radiation. Intensity modulated radiation therapy (IMRT) was adopted from 2005 onward. RESULTS: Fifty-eight patients were eligible; the median age was 32 years. Seventy-six percent of tumors (n = 45) were parameningeal and 45% (n = 26) were >5 cm. Of 45 patients with M0 HNRMS treated with curative intent, 33 (73%) were E/A-HNRMS and 12 (27%) P-HNRMS. Patients with E/A-HNRMS received definitive RT with 66 to 70 Gy in 2 Gy per fraction. Elective nodal RT was routinely delivered. In the pre-IMRT era (before 2005), 12 of 23 (52%) patients with M0 E/A-HNRMS experienced locoregional recurrences. In the IMRT era (2005 and onward), 1 of 10 patients (10%) with M0 disease recurred locally; this patient achieved a complete clinical response despite a 3-week interruption after 48 Gy because of local toxicity but experienced an in-field local recurrence 45 months later that resulted in death. Locoregional control was superior in the IMRT era vs pre-IMRT era (P = .049). Distant metastasis among patients with E/A-HNRMS was the predominant mode of treatment failure (n = 17 of 33, 52%). CONCLUSIONS: Our study shows a high rate of locoregional control for adult E/A-HNRMS following definitive CRT using IMRT, and CRT should be considered for the majority of patients in this population. In contrast, P-HNRMS is distinct and requires surgery +/– RT.