SAMHD1 and Familial prostate cancer: At the gene level, our case-control collapsing analysis confirms associations between rare damaging variants in four genes and increased prostate cancer risk: SAMHD1, BRCA2 and ATM at the study-wide significance level (P < 1×10−8), and CHEK2 at the suggestive threshold (P < 2.6×10−6).