Parameningeal rhabdomyosarcoma: results of an international workshop

A retrospective analysis was performed on children with nonmetastatic rhabdomyosarcomas (RMS) involving a parameningeal site treated by one of the four major cooperative groups: Intergroup Rhabdomyosarcoma Study (IRS), International Society of Pediatric Oncology (SIOP), German Cooperative Group (CWS), and Italian Cooperative Group (ICS) to analyse survival and prognostic factors.

Between 1979 and 1989, 230 children (median age 6 years) were treated in the IRS III, SIOP 84, CWS 81, and ICS 79 studies. All patients received chemotherapy, and 203 were irradiated. Radiotherapy doses were similar in the four studies, although treatment volumes were not similar. The SIOP patients had smaller volumes treated. In addition, the SIOP patients with a low risk of meningeal involvement and children under 5 years of age were not irradiated if they had a complete response (CR) to chemotherapy. Time to initiation of irradiation was earlier in the IRS and Italian studies.

Median follow-up was 62 months (range 22-140). The 5-year survival and 5-year event-free survival were better for the IRS study (74% and 71%) than for the other study groups (55% and 36% for SIOP, 47% and 47% for CWS, and 39% and 39% for ICS). The low-risk (LR) patients in the IRS study had improved survival. However, patients with high risk of meningeal involvement had similar survival in all four studies. The most significant prognostic factor was the size of tumor (> 5 cm).

The improved results from the IRS group, especially among the LR patients, could be related to the IRS treatment employed, particularly the systematic use of radiation, to the inclusion of patients with smaller tumors, and to the routine use of quality control of radiation.