Adult Rhabdomyosarcoma: Clinical Features and Radiotherapy Outcomes-The Turkish Oncology Group (TOG) Bone and Soft Tissue Sarcoma Study Group

OBJECTIVE Although rhabdomyosarcoma (RMS) is the most frequent soft tissue sarcoma diagnosed in childhood, it represents only 2%-5% of adult soft tissue sarcomas. The aim of the present study was to better understand the clinical characteristics, treatment approaches, and outcomes of patients with adult RMS who received radiotherapy (RT) as a component of their multidisciplinary management since there are scarce data on adult RMS due to its rarity. METHODS The medical records of patients with adult RMS who were >= 18 years old and treated with RT between January 1995 and August 2016 in four different radiation centers were evaluated in terms of clinical characteristics, treatment, and follow-up data retrospectively. RESULTS There were 28 patients. The median age at diagnosis was 28 (19-53) years. The most common site of involvement was the head and neck (25%), and parameningeal region involvement was prominent (92%) among them. In general, unfavorable site of involvement was markedly higher than favorable ones (82% vs. 18%). Alveolar and pleomorphic subtypes compromised 75% of the cases. Fifteen patients had surgery, 26 chemotherapy, 10 radical intent of RT, 9 adjuvant, 3 preoperative, and 6 palliative. The follow-up time was from 3 to 235 (median 18) months, disease-free survival was between 2 and 48 (median 12) months, and 5-year overall survival (OS) was 25% (median OS 20 (4-235) months). There were significant differences in terms of survival according to histopathological subtypes (p: 0.017), risk groups (p<0.001), Intergroup Rhabdomyosarcoma Study Group (IRSG) grouping and IRSG staging (p<0.001). CONCLUSION Adult RMS has unfavorable clinical presentation and worse outcome compared with pediatric RMS. Histopathological subtype and risk grouping to define the prognosis used in pediatric cases also might be valid in adult RMS.