Rhabdomyosarcoma Outcomes Improved with Maintenance Therapy

At the 2018 American Society of Clinical Oncology (ASCO) Annual Meeting, the European Paediatric Soft Tissue Sarcoma Study Group (EpSSG) presented data on the RMS2005 maintenance study (Abstract LBA2), which indicated that adding 6 months of low-dose maintenance chemotherapy after standard intensive therapy improves survival in children with high-risk rhabdomyosarcoma.

The use of the maintenance regimen increased both 5-year disease-free survival (DFS) and 5-year overall survival (OS).

“Maintenance therapy is an effective and well-tolerated treatment for children with high-risk rhabdomyosarcoma, and our group has decided that this is the new standard treatment for patients, at least in Europe,” Gianni Bisogno, MD, of the University Hospital of Padova, Italy, shared in his presentation.

The trial was designed to establish whether maintenance metronomic chemotherapy would improve patients’ survival with nonmetastatic rhabdomyosarcoma defined as high-risk based on EpSSG stratification. At the 108 centers in 14 countries, inclusion criteria for the study included previously untreated patients from age 0 to 21 with pathologically proven high-risk rhabdomyosarcoma with no evidence of metastasis.

If no radiologic evidence of tumors was found after standard intensive therapy, which included 9 cycles of high-dose chemotherapy, radiotherapy, and surgery, patients were then randomly assigned to either terminate treatment (186 patients) or progress with 6 months of maintenance therapy (185 patients).

Six 28-day cycles of intravenous vinorelbine 25 mg/m² on days 1, 8, and 15 of each cycle, plus daily oral cyclophosphamide 25 mg/m² were included the low-dose maintenance therapy. DFS served as the primary endpoint was DFS while OS served at the secondary endpoint.

Three hundred and seventy-one of the 670 patients assessed for eligibility were randomly assigned to the standard treatment arm or the maintenance arm. Less anemia and thrombocytopenia were seen in the maintenance arm compared with the standard intensive therapy. Additionally, fewer infections occurred, and no cardiac, hepatic, or renal toxicity reported in the maintenance arm compared with intensive therapy.

According to the results, the 5-year DFS was 77.6% in the maintenance group and 69.8% in the standard treatment group (HR 0.68, 95% CI [0.45, 1.02]; p = 0.0613) while the 5-year OS was 86.5% in the maintenance group and 73.7% in the standard treatment group (HR 0.52, 95% CI [0.32, 0.86]; p = 0.0111). Increases of approximately 8% in DFS and approximately 13% in OS over standard treatment with the maintenance regimen contributed to the disparities.

However, Dr Bisogno added that the trial was undertaken to improve outcomes for these high-risk patients. Thus, most patients that have a recurrence after initial treatment cannot be cured.

Rhabdomyosarcoma is a tumor of mesenchymal origin found most commonly in children. However, it can also occur in adults. With only about 350 children diagnosed in the United States and 320 in the European Union annually, it is considered a rare disease. Despite the tumor’s reputation of an aggressive nature, about 70% to 80% of children can obtain complete remission with intensive treatment that includes high-dose chemotherapy, radiation, and surgery.

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