Concordance of Non-Low-Risk Disease Among Pairs of Brothers With Prostate Cancer

Purpose Prostate cancer among first-degree relatives is a strong risk factor for diagnosis of prostate cancer, and the contribution of heritable factors in prostate cancer etiology is high. We investigated how the concordance of non-low-risk prostate cancer among brothers is affected by their genetic relation. Methods We identified 4,262 pairs of brothers with prostate cancer in the Prostate Cancer Database Sweden. Their cancers were categorized as low risk (Gleason score ≤ 6; clinical stage T1-2, Nx/N0, Mx/M0; and prostate-specific antigen ≤ 10 ng/mL) or non-low risk. The odds ratio (OR) for concordance of non-low-risk cancer was calculated with logistic regression for the different types of fraternity (monozygotic twins, dizygotic twins, full brothers, and half-brothers) Results Among monozygotic twins who both were diagnosed with prostate cancer, the OR for both brothers being in the non-low-risk category was 3.82 (95% CI, 0.99 to 16.72) after adjusting for age and year of diagnosis. Among full brothers, the corresponding adjusted OR was 1.21 (95% CI, 1.04 to 1.39). When the analysis was restricted to brothers who both were diagnosed within 4 years, the results were similar. Conclusion Non-low-risk prostate cancer has a heritable pattern suggesting shared genetic factors, with the highest concordance among monozygotic twins. Our results suggest that a man whose brother has been diagnosed with a non-low-risk prostate cancer is at a clinically relevant increased risk of developing an aggressive prostate cancer himself.