Sequential high-dose chemotherapy for children with metastatic rhabdomyosarcoma

The RMS4.99 study was designed to explore the role of multiple sequential high-dose chemotherapy cycles administered early in the treatment of children with metastatic rhabdomyosarcoma.

Seventy patients were enrolled and received three cycles of initial standard chemotherapy, followed by a course of cyclophosphamide and etoposide to obtain peripheral blood stem cells (PBSC), then three consecutive high-dose combinations followed by PBSC rescue. This was followed by surgery and/or radiotherapy, after which a final maintenance treatment with six courses of vincristine, actinomycin D and cyclophosphamide was administered.

Sixty-two patients underwent the high-dose chemotherapy phase. The 3-year overall survival (OS) and progression free survival (PFS) rates for the 70 patients were 42.3% (95% confidence interval [CI] 39.5-53.6) and 35.3% (95% CI, 24.3-46.5), respectively. By multivariate analysis survival correlated strongly with age > 10 years. In a subset of patients with only one or no unfavourable prognostic factors (age > 10 years, unfavourable site of primary tumour, bone or bone marrow involvement and number of metastatic sites >2) the PFS was significantly higher, i.e. 60.5% at 3 years.

Our study confirms that patients with favourable prognostic characteristics have a better survival. The use of sequential cycles of high-dose chemotherapy did not appear of benefit for patients with metastatic rhabdomyosarcoma.