Group II rhabdomyosarcoma and rhabdomyosarcomalike tumors: is radiotherapy necessary?

Purpose: In the prospective Cooperative Soft Tissue Sarcoma Study Group (CWS) 81, 86, 91, and 96 trials, radiotherapy was omitted in some patients with rhabdomyosarcoma and rhabdomyosarcoma-like tumors within Intergroup Rhabdomyosarcoma Study (IRS) group II. This analysis evaluates whether subgroups can be defined for which radiotherapy is not necessary.

Patients And Methods: Two hundred three patients who were registered between January 1981 and December 1998 were eligible for evaluation. Radiotherapy was given depending on tumor location, histology, and whether a secondary complete resection could be performed. The recommended radiation doses ranged from 32 to 54 Gy.

Results: One hundred ten patients did receive and 93 patients did not receive radiotherapy. The calculated local control after 5 years was 83% with and 65% without radiotherapy (P <.004). Event-free survival (EFS) at 5 years was 76% and 58%, respectively (P <.005). Overall survival (OS) at 5 years was 84% and 77% (P = not significant). The differences in local control were significant for the subgroups of irradiated patients with favorable histology, favorable site, and initial tumor size of less than 5 cm. A trend for improved local control with irradiation was observed for patients with unfavorable site, unfavorable histology, and large primary tumors. EFS was significantly improved for irradiated patients who had unfavorable histology, both favorable and unfavorable tumor sites, and small initial tumors. OS was significantly improved for patients with unfavorable histology through radiation.

Conclusion: Local control and EFS in group II patients are improved with radiotherapy. No subgroup could be defined for which the omission of radiotherapy produced outcome equivalent to that of patients who were irradiated.