Comparison of results of a pilot study of alternating vincristine/doxorubicin/cyclophosphamide and etoposide/ifosfamide with IRS-IV in intermediate risk rhabdomyosarcoma: a report from the Children's Oncology Group.

BACKGROUND: Over 50% of patients with rhabdomyosarcoma (RMS) have intermediate risk disease, with a 3-year failure-free survival (FFS) of 50%-70% depending on histology. Doxorubicin is active against RMS, but its role in improving outcome remains controversial. Ifosfamide is as active as cyclophosphamide in RMS, with the Fourth Intergroup RMS Study (IRS-IV) showing equivalent outcomes for patients treated with ifosfamide for the first 28 weeks compared to cyclophosphamide. Treatment with alternating cycles of non-cross-resistant chemotherapy has been used in a number of diseases with good results.

PROCEDURE: The results of a pilot study utilizing alternating courses of vincristine, doxorubicin, cyclophosphamide, and etoposide/ifosfamide (VDC/IE) were compared for outcome and patient characteristics to a group of similar matched patients treated on IRS-IV.

RESULTS: The 5-year FFS for patients with parameningeal (PM) primaries on IRS-IV and the VDC/IE study were 72% and 82%, respectively (P = 0.26); for patients with non-PM primaries, the estimated risk of failure for VDC/IE study versus IRS-IV was 0.54. Combining all disease sites and performing analysis for relative risk of failure for 46 VDC/IE patients and 342 IRS-IV patients, the relative risk of failure for the VDC/IE study compared to the IRS-IV study is 0.5 (P = 0.06).

CONCLUSIONS: VDC/IE is as effective therapy for intermediate risk RMS as IRS-IV therapy. It is being explored along with irinotecan in relapsed patients and newly diagnosed high-risk patients.