Medical Reading

The Influence Of Serial Prostate-Specific Antigen (PSA) Screening On The PSA Velocity At Diagnosis

November 06, 2017

UroToday - The PSA test is now a widely used test for screening men for prostate cancer in the United States. Since it was first introduced more than 20 years ago, the most common presentation of a man with newly diagnosed prostate cancer has changed dramatically. Compared to the era before PSA, he is younger, has less aggressive cancer, and his tumor stage is more favorable. With these lower-risk factors, one would naturally assume that he is likely to have a better outcome from the standpoint of his cancer: specifically, he should live longer. This point is surprisingly hard to prove because while men diagnosed earlier may be curable, it remains unclear as to whether curability would have been lost had then been diagnosed later based on DRE alone. Therefore, while there have been clear changes in how men present with prostate cancer, we do not yet know if screening with the PSA test will lead to longer survivals. There are clinical trials which will go a long way towards answering this question but their results are not yet known. In the meantime, we can use circumstantial evidence to help better understand whether the PSA test will improve men's survival.

It is now understood that in addition to the level of PSA, there is important information in how rapidly the PSA value increases over time. An increase of greater than 2 points over a one year period before the diagnosis has been related to a worsened outcome. While other factors related to the prognosis of men with prostate cancer have improved over time since the introduction of the PSA test, it was not known whether there has been a change in how many men are presenting with this rapidly increasing PSA.

In an attempt to better understand these issues, we looked at a group of men who had enrolled in a large PSA screening trial. They all had regular PSA tests and physical exams and if prostate cancer was diagnosed, men underwent a radical prostatectomy. To identify differences in men's disease status at diagnosis over time, we grouped them into three time periods depending on the date they were diagnosed. We then looked at the PSA (both the level and whether it had increased greater than 2 points in the year prior to diagnosis), Gleason score, and clinical stage of the men across these three time periods. With regards to the PSA level, Gleason score and tumor stage, our results showed what others have found, that over the 14 years of the study, men presented with smaller, less aggressive tumors and lower PSA values. What this study showed for the first time was that over the three time periods there were also fewer and fewer men with rapidly rising PSA values at the time of diagnosis. Specifically, in those men diagnosed between 1989-1995, 35% had a PSA which had increased more than 2 points in the prior year compared to 22.5% and 11.6% in the time periods between 1995-1998 and 1998-2002 respectively. This difference was statistically significant. These data support, but do not provide conclusive evidence, that screening with the PSA test will result in longer survival.

Because this study did not look specifically at what happened to the men after their diagnosis, the results should not be viewed as a final answer to this important question. The complexity of this issue has led to large prospective trials which we expect will provide the clearest picture of whether PSA screening will lead to longer survival. Such trials have been completed but the results are not yet known. In the meantime, this and other similar studies can be used by men and their physicians to discuss the risks and benefits of routine PSA screening.

Neil E. Martin, MD, as part of Beyond the Abstract on UroToday.

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