What’s new in prostate Ca tests: Markers, imaging
Men in the United States have about a 1 in 7 lifetime chance of being diagnosed with prostate cancer, but many of these men will have indolent disease that has a low likelihood of ever causing clinical symptoms. Now a number of diagnostic modalities are available that provide prognostic information to aid urologists and patients with decisions about biopsy and management of prostate cancer. These tools include a variety of urine-, blood-, and tissue-based laboratory tests assaying various prostate cancer biomarkers along with magnetic resonance imaging (MRI), with many additional diagnostics emerging.
In this article, urologists Scott E. Eggener, MD, and Stacy Loeb, MD, MSc, discuss the current applications for biomarkers and MRI, their impact on clinical practice, and future developments.
The biomarkers for prostate cancer with direct relevance to practicing urologists fall into several categories defined by the clinical scenario where they are used. They include tests for early detection to help the decision about having an initial or repeat biopsy after a previously negative result, tests providing information for risk stratification to guide initial management decisions in men newly diagnosed with clinically localized prostate cancer, and tests to help inform decisions about adjuvant radiation following radical prostatectomy. Not discussed in this article are prostate cancer biomarker tests used by medical oncologists to help with targeted treatment selection for existing metastatic disease.
The NCCN Guidelines Version 2.2016 for Prostate Cancer Early Detection recommends consideration of percent free PSA, Prostate Health Index (phi), and 4Kscore in men with a PSA >3.0 ng/mL who have not yet had a biopsy. Mi-Prostate Score (MiPS) and SelectMDx are other new tests that can be used to assist the decision of whether or not to perform an initial biopsy in men with an elevated PSA.
The current NCCN guidelines state percent free PSA, phi, 4Kscore, PCA3, and ConfirmMDx may also be considered for men who have had at least one prior negative biopsy and are thought to be at higher risk. SelectMDx, MiPS, or MRI of the prostate can also be used in this setting.
A greater percent of PSA circulating in the free form indicates a lower risk of prostate cancer and aggressive disease. The percent free PSA test has been around since the 1990s and is a widely available second-line testing option.
phi is a blood test that reports probability of having prostate cancer detected on biopsy based on measurement of total, free, and p2PSA ([-2]proPSA). Nomograms are available combining phi with other risk factors to predict aggressive prostate cancer.
4Kscore, also a blood test, measures free, total, and intact PSA along with human kallikrein 2 and takes into account age, digital rectal exam results, and prior biopsy status to calculate a percent likelihood of finding high-grade (Gleason ≥7) cancer on biopsy.
Prostate Cancer Antigen 3 (PCA3) is a urine test that assays for a noncoding, prostate tissue-specific RNA that is overexpressed in prostate cancer. It generates a score reflecting likelihood of a positive biopsy.