MyProstateScore (MPS; also referred to as Michigan Prostate Score) combines serum prostate-specific antigen (PSA) levels with the urinary biomarkers prostate cancer antigen 3 (PCA3) and TMPRSS2: ERG gene fusion to estimate the risk of prostate cancer. MPS is marketed as a tool for determining the likelihood of detecting clinically significant prostate cancer on biopsy.^1–3 It may help patients and physicians decide whether to proceed with a prostate biopsy.

Accuracy

The biomarkers PCA3 and TMPRSS2: ERG have each been studied independently to determine their clinical utility. In a 2020 systematic review and meta-analysis of 54 studies (N = 17,575) that included 4,043 patients with a prostate cancer diagnosis, a PCA3 score of 35 was 71% sensitive (95% CI, 67% to 74%) and 68% specific (95% CI, 63% to 74%) for diagnosing prostate cancer, with a positive likelihood ratio of 2.25 (95% CI, 1.93 to 2.61) and negative likelihood ratio of 0.43 (95% CI, 0.38 to 0.47).⁴ Although the review was limited by marked heterogeneity of sample sizes and analysis methods, the authors concluded that PCA3 has moderate diagnostic accuracy.⁴

In a 2018 meta-analysis (N = 1,057), the presence of urinary TMPRSS2: ERG was associated with a histologic diagnosis of prostate cancer (odds ratio = 2.79; 95% CI, 1.12 to 6.98; eight studies); however, there was marked heterogeneity that the authors could not adequately explain.⁵ In addition, validity was limited because the included studies were a mix of randomized controlled trials and cohort, case-control, and cross-sectional studies of patients undergoing prostate biopsy or resection, for which the indications were not clearly described.⁵

In a prospective cohort of 1,225 individuals presenting for a prostate biopsy, the area under the curve (AUC) was used to compare PSA with MPS. The AUC for MPS was greater than for PSA alone in the detection of prostate cancer (0.751 vs. 0.585, P < .001).² An AUC of 0.5 is considered to be of limited diagnostic utility. An AUC of 0.7 to 0.8 is generally considered good diagnostic accuracy, 0.8 to 0.9 is excellent, and greater than 0.9 is outstanding.⁶

MPS may be useful for identifying high-grade prostate cancer (i.e., grade group 2 or higher ^7,8) in those presenting for prostate biopsy.^1,3 In a large validation study that combined two external cohorts of 1,525 total patients referred for their first prostate biopsy (338 of the patients [22%] had confirmed grade group 2 or higher cancer), an MPS threshold score of 10 was 97% sensitive for detecting high-grade cancer, with a negative predictive value of 97.5%.¹ Using an MPS threshold score of less than 10 would have avoided 387 unnecessary biopsies for the 1,187 patients (32.6%) whose biopsies were normal or grade group 1 and would have missed only 10 high-grade cancers (3%).1 Limitations of the study include the use of prostate biopsy as a reference standard because it is known to miss clinically significant cancers and detect those that are clinically insignificant. Furthermore, the study did not incorporate other diagnostic testing capabilities such as magnetic resonance imaging, which is increasingly used in the diagnosis of prostate cancer.¹

Benefit

MPS may reduce biopsies in the evaluation of suspected prostate cancer.^1,2 The initial derivation study applied mathematical models that suggest the use of MPS would avoid 35% to 47% of biopsies.² This finding is similar to that of a prospective cohort study, which found that 33% of prostate biopsies could have been avoided in patients with an MPS of less than 10.¹ It should be noted that these predictive models have not been studied outside of patients presenting for prostate biopsy.^1,2

Harms

The MPS test includes a blood draw for PSA, and a urine sample for PCA3 and TMPRSS2: ERG should be collected within one hour after a digital rectal examination that includes a prostate massage.^3,9 In the two prospective cohort studies from which the clinical decision tool was derived, the missed diagnosis rate was 1% to 3.7% for grade group 2 or higher cancers.^1,2