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Advanced prostate cancer rate could triple without PSA testing
The number of men who present with advanced prostate cancer at the time of diagnosis could triple if PSA screenings were eliminated, according to study results.
Prostate cancer is the second leading cause of cancer death in men. Some case-control studies have suggested screening may reduce prostate cancer mortality or the risk of metastatic disease due to early detection, but other studies have shown no association. Thus, PSA testing remains controversial.
In May, the US Preventive Services Task Force recommended against the screening for all healthy men, regardless of age. The government panel determined doctors over-diagnose and over-treat patients with nondeadly forms of prostate cancers, putting those patients at risk for serious adverse effects such as urinary and erectile dysfunction.
A couple months later, ASCO issued an opinion recommending that men with a life expectancy of more than 10 years discuss PSA testing with their physicians.
For this study, researchers estimated the number of patients who would present with metastatic prostate cancer in a given year if age-specific and race-specific incidence rates were the same as they were in the pre-PSA testing era.
Edward M. Messing, MD, chair of urology at the University of Rochester Medical Center and president of the Society of Urologic Oncology, and colleagues analyzed information from the SEER cancer registry from 1983 to 2008.
Researchers examined SEER data for the years before routine PSA testing (1983-1985) and compared it with data from the era of widespread PSA testing (2006-2008).
Researchers adjusted for age, race and geographic variations in the US population.
They designed a mathematical model that used the incidence rates of men who presented with advanced prostate cancer at diagnosis during the pre-PSA era and estimated the number of metastatic cases that would have occurred in 2008 had PSA screening not existed.
According to the results, 739 men in the SEER registry presented with metastatic prostate cancer in 2008. The expected number of men with metastatic prostate cancer in the absence of screening was 2,277 (expected-to-observed ratio = 3.1; 95% CI, 3.0-3.2).
In 2008, the most recent year for which SEER data was available, researchers found an estimated 8,076 cases of metastatic prostate cancer at initial diagnosis for the US population.
Using the mathematical model, Messing and colleagues estimated that more than 25,000 men would have presented with metastatic prostate cancer upon initial diagnosis — about three times more than the number actually observed — had PSA testing not been available.
Messing and colleagues said the results had limitations, including not knowing whether risk factors such as obesity influenced the incidences of advanced prostate cancer during the study period.
Still, the study findings are important when considering the recent controversy over PSA screening, Messing said.
“Yes, there are trade-offs associated with the PSA test and many factors influence the disease outcome,” Messing said in a press release. “Yet our data are very clear. Not doing the PSA test will result in many men presenting with far more advanced prostate cancer, and almost all men with metastasis at diagnosis will die from prostate cancer.”
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Perspective
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The recent paper by Scosyrev and colleagues raises important — and sobering — questions about issues involved in the management of patients with prostate cancer. The important question: The authors hypothesized that a recommendation to reduce or cease PSA screening for prostate cancer would substantially increase the likelihood of patients being initially diagnosed with prostate cancer with metastatic (M1) disease. Using SEER data, they estimated the number of M1 patients that would have been diagnosed in 2008 if PSA screening were not available. They based this estimate on data from 1983-1985, an interval in the pre-PSA era. The methodology of this analysis is sound and the hypothesis intriguing. In 2008, the observed number of men presenting with M1 prostate cancer in the SEER 9 registries area was 739; in contrast, 2,277 men would have been expected, based on 1983-1985 SEER data. This yielded an expected-to-observed ratio of 3.1 (95% CI, 3.0-3.2). Applying this ratio to the total US population — an exercise always undertaken to dramatize the impact of findings, especially hypothetical findings — in 2008 suggested that the total number of men presenting with M1 prostate cancer in that year would be about 25,000 instead of the approximately 8,000 actually observed. The authors point out the appropriate caveats regarding the unknown confounding variables and the concern that lead time bias might result in these findings failing to impact OS of patients. The sobering knowledge gaps in our management of prostate cancer patients this paper raises in this reviewer’s mind are:
1. The reason to do this analysis in the first place is conditioned by the lack of less confounded data derived from randomized controlled trials demonstrating improved survival — or not — following PSA screening.
2. The limited amount of high-quality, widely accepted data on the role of androgen deprivation applied “early” in the course of prostate cancer:
a. M1 disease?
b. PSA-only disease?
c. Patients at high risk of recurrence following local therapy, especially radical prostatectomy?
Because of these difficulties, the analysis of these authors should redouble our efforts to improve our ability to define good- and poor-prognosis patients, to answer less equivocally the question regarding the utility of PSA screening, and to determine how best to use our increasingly effective approaches to androgen deprivation in order to clearly improve our care of men with prostate cancer.
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