Sequential intensified chemotherapy with stem cell rescue for children and adolescents with desmoplastic small round-cell tumor

The RMS4.99 study was designed to explore the role of early sequential intensified chemotherapy (SICT) with PBSC rescue in patients with soft tissue sarcoma with a poor prognosis. Fourteen patients with desmoplastic small round-cell tumor (DSRCT) were included in this study. Initial chemotherapy was followed by a course of CY and etoposide with subsequent PBSC harvest, then three consecutive intensified chemotherapy combinations followed by PBSC rescue and G-CSF administration: first cycle thiotepa (150 mg/m² × 2 on day 1) and melphalan (60 mg/m² on day 2), second cycle CY (2 g/m² on days 1 and 2) and thiotepa (150 mg/m² × 2 on day 3), third cycle melphalan (80 mg/m² on day 1). The interval between cycles had to be kept as short as possible. Then patients underwent surgery or radiotherapy or both, after which six courses of vincristine, actinomycin D, CY were administered. Ten patients received SICT, which was well tolerated. With a median follow-up of 27 months only three patients are alive without evidence of disease. The 3-year event-free and overall survival rates were 15.5 and 38.9%, respectively. The prognosis for pediatric patients with DSRCT did not improve after administering intensified chemotherapy early in their treatment, so different strategies are needed.