The Rotterdam Prostate Cancer Risk Calculator (RPCRC) and Stockholm3 can both be used to aid urologists in their decision to refer men to magnetic resonance imaging (MRI) or biopsy for early detection of prostate cancer. The objective of the study was to assess the external validity of the RPCRC and compare it with using PSA and Stockholm3 to detect clinically significant prostate cancer. Using data from the prospective, population-based, randomized STHLM3-MRI screening trial, 666 participants were included and the probabilities for clinically significant prostate cancer (csPC) were calculated for each participant using the RPCRC and Stockholm3, with and without prostate volume.

Using RPCRC’s recommended risk threshold of ≥4 percent for finding csPC, 54 percent of all csPC cases would be detected versus 94 percent using Stockholm3 with a threshold of ≥11 percent. Calibration of Stockholm3 was adequate while RPCRC underestimated the risk of csPC. The Stockholm3 test showed positive net benefits at clinically relevant thresholds, while the RPCRC showed negative net benefits. Compared with PSA, the RPCRC was associated with lower detection of csPC (84 vs103), while Stockholm3 was associated with higher detection of csPC (143 vs 103).

“This study further validates the clinical benefits of Stockholm3 compared to other methods, and a significant potential to improve prostate cancer diagnostics in Europe by finding more cases early, when the patient can be cured. Including Stockholm3 in both guidelines and clinical practice can save substantial costs and free up resources by reducing overdiagnosis. We are already active in Sweden, Norway, Finland, Germany and Switzerland and will target the rest of Europe in our expansion,” says David Rosén, CEO of A3P Biomedical.

(1) External Validation of the Rotterdam Prostate Cancer Risk Calculator and Comparison with Stockholm3 for Prostate Cancer Diagnosis in a Swedish Population-based Screening Cohort; Palsdottir et al, European Urology Focus 2022.