Characteristics of Secondary Muscle-Invasive Bladder Cancer (MIBC) Following Pelvic Irradiation - Expert Commentary

Radiation therapy is commonly used for the definitive and palliative treatment of pelvic malignancies. Secondary pelvic cancers have been reported after radiation therapy, including radiation-associated muscle-invasive bladder cancer (RA-MIBC). The treatment of these cancers poses a challenge due to their inherent resistance and the risk of surgical and re-irradiation options.

A recent study by Sha and colleagues queried the Surveillance, Epidemiology, and End Results (SEER) database to highlight the clinical characteristics and long-term outcomes of patients with RA-MIBC. The investigators identified a total of 1093 who were previously exposed to pelvic radiation therapy. Compared to primary MIBC, RA-MIBC patients were more likely to be older males previously treated for prostate cancer and to present with T4 disease at diagnosis (21.0% vs 17.3%, P < .001). For local therapy, patients with RA-MIBC were less likely to be candidates for radiation therapy or radical cystectomy.  The median time to the development of RA-MIBC after radiation for the primary malignancy was eight years. RA-MIBC patients had higher 5-year bladder cancer-specific mortality across all subgroups (56.1% vs 35.3%,  adjusted hazard ratio 1.24, P < .001) when compared to matched primary MIBC patients.

Despite the limitations of the study, it clearly emphasizes the distinct natural history of RA-MIBC. Rigorous studies examining the molecular characteristics of  RA-MIBC are needed to understand the biology of these aggressive tumors.

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

References:

  1. Sha ST, Dee EC, Mossanen M, Mahal BA, Zaslowe-Dude C, Royce TJ, Hirsch MS, Sonpavde G, Preston MA, Nguyen PL, Mouw KW, Muralidhar V. Clinical characterization of radiation-associated muscle-invasive bladder cancer. Urology. 2021;doi.10.1016/j.urology.2021.03.033. PMID: 33857569

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