Clinical Outcomes of Adult Patients with Kidney, Bladder, and Prostate Rhabdomyosarcoma - Expert Commentary

Rhabdomyosarcoma (RMS) is a soft tissue tumor that commonly occurs in childhood and adolescence. It is less prevalent in adulthood, accounting for 2%–5% of adult soft tissue tumors. RMS has a higher propensity to occur in genitourinary organs in adults than in pediatric patients. The clinical outcomes of adult patients with kidney, bladder, and prostate RMS is unknown.

A recent study by Patel et al., published in Rare Tumors investigated the epidemiology and prognostic factors of patients with kidney, bladder, and prostate RMS. The authors queried the Surveillance, Epidemiology, and End Results (SEER) database from 1973 to 2016 for patients >18 of age with RMS. The search retrieved a cohort of 14 kidney, 35 bladder, and 21 prostate RMS adult patients.

The bladder RMS patients tended to have older age at diagnosis than kidney and prostate (65 vs. 52.5 and 42 years). The extent of the disease was similar at presentation among the three groups. The five-year overall survival (OS) for adult kidney, bladder, and prostate RMS was 17.1% (95% confidence interval [CI]: 2.9–41.6%), 22.2% (95% CI: 11.6– 9.4–38.4%), and 33.0 ((95% CI: 11.6– 12.8–55.0%). There was no statistical difference in overall survival between the three groups (p = 0.209). In multivariable analysis, kidney RMS patients tended to have a higher risk of mortality (hazard ratio [HR]: 2.16, 95% CI 1.03–4.53) compared to bladder RMS. Mortality from prostate RMS was not significantly different from bladder RMS. The extent of the disease and older age were significant predictors of worse OS in the multivariable analysis for all groups.

Generally, adults diagnosed with genitourinary RMS had poor outcomes. One of the critical variables that were not included in the multivariable analysis is the type of systemic therapy used. The treatment of adult genitourinary RMS is primarily extrapolated from pediatric regimens. Although the extent of disease pattern at presentation was similar to pediatric RMS, adult genitourinary RMS outcomes were worse. This suggests that other factors play a critical role in determining the clinical course of RMS in adult patients. Understanding the biological differences between adult and pediatric RMS is needed to design future therapeutic trials to improve outcomes.

Written by: Bishoy M. Faltas, MD, Director of Bladder Cancer Research, Englander Institute for Precision Medicine, Weill Cornell Medicine, New York City, New York

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