The USA Preventive Services Task Force recently published a draft recommendation discouraging PSA testing (screening) as an intervention for reducing prostate cancer deaths . In large part, this recommendation was based on the fact that PSA testing leads to the detection of biologically indolent prostate cancers that would remain undetected during life if screening had not taken place (over diagnosis). Rather than discarding the PSA test altogether, many investigators are seeking methods for improving the ability of PSA to detect aggressive disease for which treatment would improve overall health. One such approach called PSA velocity (PSAV) risk count is the topic of the present report by Loeb et al.
Urologists recognise the wide variability in PSA level from measurement to measurement (‘noise’) that makes interpretation of PSA changes over time (PSAV) challenging . They also recognise that a continuously rising PSA level can signal the presence of prostate cancer . For this reason, in 2007 we introduced a concept referred to as the PSAV risk count, or the simple number of times a PSAV threshold (the ‘speed limit’) was exceeded . The PSAV risk count was significantly associated with the development of aggressive prostate cancer in an ageing study .
In the present study, the PSAV risk count was evaluated for the first time in a large screening cohort that has been the setting for many of the discoveries related to PSA testing over two decades . The authors confirmed that the PSAV risk count using a threshold of 0.4 ng/mL/year (the ‘speed limit’) was significantly associated with the presence of prostate cancer. As compared with a risk count of 0–1, a risk count of 2 was associated with an 8-fold increased odds of prostate cancer; but more importantly a 5-fold increased odds of Gleason score ≥8. The PSAV risk count improved the prediction of high-grade disease in two separate analyses after accounting for PSA level and age (Figs 2,3). From the patient perspective, in one analysis (Fig. 2) the question addressed was; ‘if I have a Gleason score 8–10 prostate cancer or not, how often does the test (PSAV risk count) result in correct classification of my disease when added to PSA and age’? In the other analysis (Fig. 3), the question addressed was; ‘given my PSAV risk count, what is the probability that I have high-grade disease’? In both situations, the answer was you want to know your patient's risk count, not just their age and PSA level.