Parameningeal rhabdomyosarcoma: outcomes and opportunities

Abstract

Purpose: To examine patterns of failure in patients with parameningeal rhabdomyosarcoma (PM-RMS) treated with intensity modulated radiation therapy (IMRT).

Methods and materials: Forty-seven patients with PM-RMS received chemotherapy and IMRT for definitive treatment. The median age was 9 years (range, 0.5-35 years). The high-risk features were as follows: 40% alveolar histology, 72% group III and 26% group IV disease, 57% either intracranial extension (ICE) (n=25) or cranial neuropathy (n=21). The median time to RT from the start of chemotherapy was 15 weeks (range, 2-54 weeks). Patients received 50.4 Gy in 1.8-Gy fractions to the primary tumor by use of IMRT. Thirteen patients aged≥14 years with alveolar histology received 36 Gy prophylactic nodal irradiation (PNI) to bilateral cervical nodes. Events were defined as local, regional (nodal), central nervous system (CNS), or distant failures.

Results: With a median follow-up time of 3.3 years (range, 0.5-12.8 years), 18 patients experienced failure: 5 local, 2 regional, 6 distant, and 7 CNS. The 5-year local failure-free survival was 86%. Age, histology, and time to RT did not influence the risk of local failure. The 5-year regional failure-free survival was 92%: 100% for embryonal and 74% for alveolar (P=.03). However, there were no lymph node failures in patients with alveolar histology who were given PNI. The 5-year CNS failure-free survival was 83%: 100% without and 70% with ICE (P=.01); 95% without and 69% with cranial neuropathy (P=.02). The estimated 5-year event-free survival and overall survival were 61% for group III and 58% for group IV patients.

Conclusions: Distant failure was the most common type of failure among group IV patients. Patients with alveolar histology seem to benefit from PNI. The presence of ICE or cranial neuropathy portends a high risk of CNS failure, the most common pattern of failure among non-group IV patients. These patients may benefit from the addition of novel CNS-directed therapy.