((B-018)) (B-018) Estimating the incidence and prevalencehe incidence of second primary malignancy in men diagnosed with prostate cancer in the US during 2000-2022, as recorded in the US SEER 17 Registries

Background: Prostate cancer (PC) is the most common cancer among adult men in the United States (US). Second primary malignancy (SPM) is a common safety topic of interest for patients receiving treatment for PC. Long-term follow-up and an analytical approach accounting for the competing risk of death is necessary for robust estimation of the risk of SPM in men with PC.

Objectives: To estimate the incidence rate (IR) of PC in men in the US during 2000-2022 and the twenty-two-year limited-duration prevalence (22YR LDP) of PC in men in the US as of 01 January 2022. To estimate the cumulative incidence of SPM in men diagnosed with PC in the US during 2000-2022.

Methods: Data from the US SEER 17 registries (~45.9% of the US population) were analyzed with SEER*Stat software (version 8.4.5.) to estimate the IR of PC in men in the US during 2000-2022 and the 22YR LDP of PC as of 01 January 2022. Age-adjusted estimates of IR and 22YR LDP were standardized to the 2000 US Standardized Population. Data from the US SEER 17 registries were analyzed with SAS Statistical Software (version 9.4.) to estimate the cumulative incidence of SPM in men diagnosed with PC in the US during 2000-2022, during follow-up periods of 6, 18, 24, 36, 48, and 60 months. This analysis accounted for the competing risk of death; results are presented overall and for the 5 most frequent sites of SPM.

Results: The crude and age-adjusted IRs of PC in men in the US during 2000-2022 were 134.2 cases per 100,000 person-years (PY) (95% confidence interval, CI: 134.0, 134.5) and 133.6 cases per 100,000 PY (95% CI: 133.3, 133.8), respectively. The crude and age-adjusted estimates of the 22YR LDP of PC in men in the US as of 01 January 2022 were 1.8% (95% CI: 1.8%, 1.8%) and 1.6% (95% CI: not reported), respectively. The cumulative incidence of SPMs in men diagnosed with PC in the US during 2000-2022 increased with longer follow-up periods, from 1.3% (95% CI: 1.3%, 1.3%) after 6 months of follow-up to 6.5% (95% CI: 6.5%, 6.6%) after 60 months of follow-up. The highest site-specific cumulative incidence of SPMs was reported for the lungs and bronchus (the cumulative incidence increased from 0.9% after 6 months to 1.2% after 60 months of follow-up), followed by the the urinary bladder (range: 0.3% to 0.9%), the kidneys (range: 0.2% to 0.5%), melanoma of the skin (range: 0.1% to 0.5%) and the pancreas (range: 0.0%, 0.3%).

Conclusions: The age-adjusted IR of PC in men in the US during 2000-2022 was 133.6 cases per 100,000 PY (95% CI: 133.3, 133.8) and the age-adjusted 22YR LDP of PC as of 01 January 2022 was 1.6%. Accounting for the competing risk of death, the cumulative incidence of SPMs in men diagnosed with PC in the US during 2000-2022 increased from 1.3% after 6 months of follow-up to 6.5% after 60 months of follow-up.