Effects of Radiation Therapy on the Incidence of Bladder Cancer and Rectal Cancer in Patients with Prostate Cancer: A Nationwide Nested Case-Control Study in Korean Population.

PURPOSE: This study aimed to assess the risk of secondary bladder and colorectal cancers following radiotherapy for prostate cancer using a nationwide nested case-control design based on Korea's Health Insurance Review and Assessment database.

MATERIALS AND

METHODS

We conducted a nationwide nested case-control study using database, including men newly diagnosed with prostate cancer between 2011 and 2020. Patients were classified into radiotherapy and non-radiotherapy groups and matched 1:1 based on age, comorbidity index, and follow-up duration. Conditional logistic regression was used to assess the association between radiotherapy and secondary bladder and colorectal cancer incidences.

RESULTS

In the crude cohort, radiotherapy was not significantly associated with secondary bladder or colorectal cancer. Kaplan-Meier analysis showed no significant differences in the cumulative incidence between radiotherapy and non-radiotherapy groups. However, nested case-control analysis revealed a significantly increased risk of secondary bladder cancer in the radiotherapy group (adjusted hazard ratio, 1.38; 95% confidence interval, 1.02 to 1.86), while no association was found for colorectal cancer (adjusted hazard ratio, 0.96; 95% confidence interval, 0.72 to 1.27).

CONCLUSIONS

Radiotherapy was linked to an increased bladder cancer risk but not colorectal cancer risk, underscoring the need for targeted long-term surveillance.