A genetic score can identify men at high risk for prostate cancer among men with prostate-specific antigen of 1-3 ng/ml

Abstract

Background: The diagnostic performance of a genetic score based on single nucleotide polymorphisms (SNPs) is unknown in the prostate-specific antigen (PSA) range of 1-3 ng/ml. A substantial proportion of men in this PSA span have prostate cancer (PCa), but biomarkers to determine who should undergo a prostate biopsy are lacking.

Objective: To evaluate whether a genetic risk score identifies men in the PSA range of 1-3 ng/ml who are at higher risk for PCa.

Design, setting, and participants: Men aged 50-69 yr with PSA 1-3 ng/ml and without a previous prostate biopsy were selected from the STHLM2 cohort. Of 2696 men, 49 SNPs were genotyped, and a polygenic risk score was calculated. Of these men, 860 were invited according to risk score, and 172 underwent biopsy.

Outcome measurements and statistical analysis: The risk of PCa was assessed using univariate and multivariate logistic regression analysis.

Results and limitations: PCa was diagnosed in 47 of 172 participants (27%), with Gleason sum 6 in 36 of 47 men (77%) and Gleason sum ≥7 in 10 of 47 men (21%); one man had intraductal cancer. The genetic score was a significant predictor of a positive biopsy (p=0.028), even after adjusting for PSA, ratio of free to total PSA, prostate volume, age, and family history. There was an increase in the odds ratio of 1.60 (95% confidence interval, 1.05-2.45) with increasing genetic risk score. The absolute risk difference of positive biopsy was 19 percentage points, comparing the high and low genetic risk group (37% vs 18%).

Conclusions: A risk score based on SNPs predicts biopsy outcome in previously unbiopsied men with PSA 1-3 ng/ml. Introducing a genetic-based risk stratification tool can increase the proportion of men being classified in line with their true risk of PCa.

Keywords: Cancer; Genetic risk; PSA; Prostate; Risk stratification; SNP.