Prostate cancer diagnostics: the independent and combined roles of SelectMDx and mpMRI

Prostate cancer is a major global health concern, affecting one in every eight men over the course of their lives. Early detection and precise risk stratification are essential for distinguishing indolent types from aggressive cancer that necessitates immediate treatment. Prostate-specific antigen (PSA), although its widespread use in prostate cancer screening, lacks specificity, resulting in unnecessary biopsies and overtreatment of clinically insignificant malignancies. The SelectMDx test, a non-invasive molecular diagnostic tool, and multiparametric magnetic resonance imaging (mpMRI) have shown promise in enhancing diagnostic precision. This study compares the independent and combination diagnostic performance of SelectMDx and mpMRI in patients with intermediate PSA levels.

A retrospective analysis of 126 patients was conducted in an academic hospital in southern Romania from 2022 to 2023. The requirements for inclusion included PSA values ≥3 ng/ml, SelectMDx evaluation, mpMRI, and a prostate biopsy. SelectMDx used mRNA expression levels of ****HOXC6 and DLX1, in addition to clinical data, to create a risk score for clinically significant prostate cancer (PCa) (grade group ≥2). PI-RADS version 2.1 was used to rate mpMRI images. Lesions with a grade of ≥3 were considered suspicious. Logistic regression models were used to determine the predictive power of SelectMDx, PI-RADS, and their combination. The diagnostic performance was assessed using sensitivity, specificity, positive predictive value, and negative predictive value. The medical relevance of reducing unnecessary biopsies has been studied using decision curve analysis.

SelectMDx showed a sensitivity of 89.2%, a specificity of 61.8%, a PPV of 49.25%, and an negative predictive value (NPV) of 93.22%. Patients with positive SelectMDx results had a 13.35-fold greater risk of clinically severe PCa (p <0.001). Using mpMRI with PI-RADS scoring improved detection of high-grade PCa. A PI-RADS score of ≥4 corresponded to a 7.13-fold higher probability of aggressive cancer (p <0.001). In multivariate analysis, adjusting for SelectMDx and patient age reduced the predictive value of PI-RADS ≥4 (adjusted OR = 1.49; p = 0.555). Standalone SelectMDx outperformed its combination with mpMRI in terms of diagnostic accuracy, as shown by higher AUC values and better DCA results.

The SelectMDx test is a highly effective and reliable diagnostic tool for predicting clinically severe PCa in individuals with intermediate PSA levels. Its high NPV avoids unnecessary biopsies and their associated morbidity. While integrating SelectMDx with mpMRI provides new diagnostic insights, the molecular test revealed superior accuracy when used alone, confirming its importance in precision medicine.