A dose-intensive multiagent regimen including dose-compressed cycles of ifosfamide/etoposide and vincristine/doxorubicin/cyclophosphamide, irinotecan, and radiation resulted in improved outcomes for patients with low-risk stage IV rhabdomyosarcoma (RMS), but not for patients with high-risk disease, according to results from the Children’s Oncology Group study.
For all patients with stage IV rhabdomyosarcoma, the 3-year event-free and overall survival rates were 38% and 56%, respectively. Patients with stage IV RMS with one or fewer Oberlin risk factors had 3-year event-free survival and overall survival rates of 69% and 79%, respectively; patients with two or more Oberlin risk factors had rates of 20% and 14%, respectively (Jour Clin Oncol. 2015 Oct 26. doi: 10.1200/JCO.2015.63.4048).
The study identified an expanded group of patients with low-risk metastatic RMS that included patients with embryonal RMS aged 10 years and older but with an Oberlin score of less than 2. The results in this group represent an improvement over previous study results. However, for the remainder of high-risk patients with alveolar RMS, different approaches are needed, according to Dr. Brenda Weigel of the University of Minnesota, Minneapolis, and her colleagues.
“Unfortunately, alveolar RMS has fewer genetic aberrations than embryonal RMS and no known recurrently mutated cancer consensus genes, which limits genetic targets available for therapeutic approaches,” they wrote.
The Children’s Oncology Group study ARST0431 enrolled 109 patients with metastatic RMS who had no prior chemotherapy or radiation treatment from 2006 to 2008.
The study combined three treatment strategies: dose intensification by interval compression, use of active agents identified in previous phase II window studies, and use of irinotecan as a radiation sensitizer. The 54-week treatment schedule began with two cycles of vincristine/irinotecan followed by interval-compressed vincristine/doxorubicin/cyclophosphamide and ifosfamide/etoposide (cycles began every 14 days), and finished with four cycles of standard vincristine/actinomycin/cyclophosphamide (VAC) and two more cycles of vincristine/irinotecan. The treatment plan also included radiation of primary and metastatic sites at week 19.
The most common nonhematologic adverse event of grade 3 or higher was diarrhea, reported in 20% of patients during the time period when they received irinotecan. Febrile neutropenia occurred in 63% of patients.
Dr. Weigel reported financial relationships with Genentech and Eli Lilly/ImClone System. Several of her coauthors reported having ties to industry sources.