The challenging role of radiation therapy for very young children with rhabdomyosarcoma.

Abstract

To evaluate local control and toxicity for very young children treated with multimodality therapy for rhabdomyosarcoma (RMS). From 1990 to 2004, 20 patients<or=36 months at diagnosis were treated at our institution. Nineteen underwent chemotherapy (CMT), surgery and/or intraoperative high-dose-rate brachytherapy (IOHDR), and external-beam radiation (EBRT). Median age was 17 months. Sites included extremity (7), trunk (5), parameningeal (4), orbit (1), head/neck (1), bladder/prostate (1). Histologies consisted of 10 embryonal (53%) and 9 alveolar/undifferentiated (47%). Ten had delayed gross total resection (GTR) at median time of 17 weeks after the start of CMT, and 8 of these underwent IOHDR. Median interval between start of CMT and EBRT was 18 weeks. Median EBRT dose was 36 Gy. EBRT technique was either intensity-modulated (11), three-dimensional (3), or two-dimensional (5). Functional outcome was assessed for patients alive>or=1 year after diagnosis (15) in terms of mild, moderate, or severe deficits. Median follow-up was 33 months for survivors and 23 months for all patients. Two-year actuarial local control, event-free survival, disease-specific survival, and overall survival were 84%, 52%, 74%, and 62%, respectively. All patients who began EBRT<or=18 weeks after the start of CMT had their disease controlled locally. Five have mild deficits and 10 have no deficits. A reduced dose of 36-Gy EBRT after delayed GTR may maximize local control while minimizing long-term sequelae for very young children with RMS, but unresectable tumors (e.g., parameningeal) require higher doses. Normal-tissue-sparing techniques such as intensity-modulated radiation therapy and IOHDR are encouraged. Local control may be maximized when EBRT begins <or=18 weeks after initiation of CMT, but further study is warranted. Longer follow-up is required to determine the full extent of late effects.