Reducing the cyclophosphamide dose for a subset of patients with rhabdomyosarcoma may increase the risk of disease recurrence, according to an article published in Cancer.1

Patients with low-risk rhabdomyosarcoma are grouped into 2 subsets by the Soft Tissue Sarcoma Committee of the Children’s Oncology Group (COG), the second of which includes patients with localized embryonal disease resected before or after chemotherapy in an unfavorable primary site or in a favorable site excluding the orbit. Patients in this subset have favorable outcomes when a total cumulative cyclophosphamide dose of 26.4 g/m2 is added to vincristine and dactinomycin.

For the part of the phase 3 study (ARST0331; ClinicalTrials.gov Identifier: NCT00075582) reported here, researchers evaluated whether reducing the total cumulative cyclophosphamide dose to 4.8 g/m2, which may reduce long-term toxicity, would preserve the clinical outcomes observed with a higher dose.

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Sixty-six eligible patients, 70% of which were younger than 5 years and 1 of which was older than 21, were enrolled. The most common primary site was the female genitourinary tract (32% of patients).

Median follow-up was 3.5 years. Failure-free survival rates were almost double that of expected results (20 failures were observed vs 10.53 expected).

Patients with genital tract disease had the worst 3-year failure-free survival rate (57%); for all other included patients this rate was 77%.

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For patients who received a higher dose of cyclophosphamide, the 3-year failure-free survival rate was 83%.

The authors noted that the results for patients with genital tract disease included in this study may be attributed to the elimination of radiotherapy combined with the lower cyclophosphamide dose. Further research is needed to determine optimal treatment regimens for subgroups within subset 2.

Reference

  1. Walterhouse DO, Pappo AS, Meza JL, et al. Reduction of cyclophosphamide dose for patients with subset 2 low-risk rhabdomyosarcoma is associated with an increased risk of recurrence: A report from the Soft Tissue Sarcoma Committee of the Children’s Oncology Group. Cancer. 2017 Feb 17. doi: 10.1002/cncr.30613 [Epub ahead of print]

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Sarcoma