Purpose: The prognosis of adult rhabdomyosarcoma (RMS) has been considered dismal. The question is raised that vincristine, d-actinomycin, and cyclophosphamide (VAC) chemotherapy may not be administered as per schedule for adult RMS; consequently, low dose intensity (DI) leads to poor prognosis. Herein, we examined whether the administration of VAC chemotherapy for adults and children with RMS is feasible with regard to the DIs of VAC.
Methods: Chart review was retrospectively performed for all identified patients. The percentage of relative DI (RDI) was calculated according to the Children's Oncology Group D9803 protocol. Further, we examined the RDI in the first 6 cycles of VAC (induction phase) and the DI after the first 6 cycles of VAC (maintenance phase).
Results: We identified a total of 27 adults and 18 children with RMS, respectively. The mean RDIs of vincristine in total phase were significantly lower in adults than that in children (P = 0.04). In induction phase, the mean RDIs of vincristine and cyclophosphamide were similar for both groups; however, they were dropped significantly in adults during maintenance phase (P < 0.05). Mean RDIs of vincristine in elderly patients tended to become low. Low RDI was mainly attributable to hematologic toxicity, infection, and peripheral neuropathy. The prognosis of low versus high RDI was similar.
Conclusions: The RDIs of vincristine and cyclophosphamide in the maintenance phase were significantly lower than that in children. VAC chemotherapy for adults was not feasible; these patients require a different regimen.