We tested the association of four PRSs (score1–4) with the risk of BC or OC development using binomial logistic regression analysis, assessing, whether the two recently developed PRS models (BayesW vs. BayesRR-RC) are effective predictors of the BC or OC risk in BRCA1 PV carriers in the Latvian population by comparing the PRS weighted effect size in mutation carriers with cancer (BC and/or OC) vs. in mutation carriers without cancer (controls). The gene discussed is BRCA1; the disease is breast cancer.