Cancer Causes Control. 2020 Aug 24. doi: 10.1007/s10552-020-01336-7. Online ahead of print.
PURPOSE: Previous studies have shown an overall decreased risk of second cancers among prostate cancer survivors, but this has not been comprehensively examined by race/ethnicity. We conducted a retrospective cohort study of 716,319 one-year survivors of prostate cancer diagnosed at ages 35-84 during 2000-2015 as reported to 17 US Surveillance, Epidemiology and End Results (SEER) registries.
METHODS: We estimated standardized incidence ratios (SIRs) for second primary non-prostate malignancies by race/ethnicity (non-Latino white, Black, Asian/Pacific Islander [API] and Latino), by Gleason, and by time since prostate cancer diagnosis. Poisson regression models were used to test heterogeneity between groups with the expected number as the offset.
RESULTS: 60,707 second primary malignancies were observed. SIRs for all second cancers combined varied significantly by race/ethnicity: SIRwhite: 0.88 (95% confidence interval: 0.87-0.89), SIRLatino: 0.92 (0.89-0.95), SIRBlack: 0.97 (0.95-0.99), and SIRAPI: 1.05 (1.01-1.09) (p-heterogeneity < 0.001). SIRs for all cancers combined were higher among survivors of higher vs. lower Gleason prostate cancers irrespective of race/ethnicity. We observed significant heterogeneity by race/ethnicity in SIRs for 9 of 14 second cancer types investigated including lung, bladder, kidney, and liver.
CONCLUSIONS: Our results confirm that most prostate cancer survivors have lower risks of second cancers than expected, but the magnitude varied by race/ethnicity. Exceptionally, API men had small but significantly increased risk. Further research to understand drivers of the observed race/ethnicity heterogeneity is warranted.