Second primary malignancy in bladder cancer: A retrospective population-based analysis.

676 Background: Bladder cancer is responsible for about 4% of cancers in the United States. It is the fourth most common cancer in men. A second primary malignancy is a significant complication in cancer survivors, with dire effects on morbidity and mortality. The data on second primary malignancies (SPM) in bladder cancer is limited. Therefore, we aim to evaluate and discuss this risk. Methods: We analyzed the Surveillance, Epidemiology, and End Results (SEER) database, comparing secondary cancer rates among bladder cancer cases diagnosed from 2000 to 2021. A second primary malignancy was defined as a malignancy developing six or more months after an index bladder cancer diagnosis. We used the SEER MP-SIR session to obtain the p-value, observed/Expected (O/E) ratio, and absolute excess risk (AER) per 10,000. Results: 238,358 bladder cancer cases from 2000-2021 met our inclusion criteria and were included in our study. Of these cases, 46,859 (19.7%) developed second primary malignancies. The mean age of SPM was 75.03 years. The risk of developing SPM was significantly higher than the general population, with an O/E ratio of 1.48 (CI 1.46-1.49, AER 99.85, p < 0.05). Most common SPMs included Hypopharynx (O/E ratio 1.3 CI 1.0-1.67, p < 0.05), Esophagus (O/E ratio 1.15 CI 1.05-1.26, p < 0.05), Liver (O/E ratio 1.14 CI 1.05-1.23, p < 0.05), Lung (O/E ratio 1.89 CI 1.85-1.93, p < 0.05), Vagina (O/E ratio 2.58 CI 1.71-3.73, p < 0.05, Prostate (O/E ratio 1.39 CI 1.36-1.42, p < 0.05, Acute Myeloid Leukemia (AML) (O/E ratio 1.58 CI 1.01-2.34, p < 0.05). Conclusions: Compared to the general population, there is a statistically significant increased risk of secondary primary malignancies in bladder cancer patients. Bladder cancer survivors would benefit from proactive screening modalities and follow-up for the development of SPM.