Dr. Marla Shapiro: To PSA screen or not to screen? We're finally getting some answers
Published Tuesday, July 24, 2012 7:31AM EDT
Six months after issuing a preliminary draft recommendation against prostate cancer screening in the form of the blood test PSA, the U.S. Preventive Services Task Force (USPSTF) has recently finalized its position: It now formally recommends AGAINST screening. It gives screening a "D" recommendation, the lowest rating.
Some commentators asked the USPSTF to change from a "D" to a "C" recommendation. which translates to "Clinicians may provide this service to selected patients... [although] there is likely to be only a small benefit.") The USPSTF responded that it did not change to "C" because it does not concede that benefits outweigh the substantial harms.
Responding to the assertion that screening probably is responsible for the observed decrease in U.S. prostate cancer mortality during the past two decades, the USPSTF replied that (a) this trend started before screening could have had an effect, and (b) many other factors, including better treatment, probably contribute to this trend.
To date, the data on PSA tests are simply insufficient to conclude that screening lowers morbidity or improves quality of life substantially.
The American Cancer Society largely agrees with the USPSTF's position. Many, however, disagree strongly.
The USPSTF document does not directly advise primary care physicians on handling PSA screening in real-life office practice. In fact, the document begins with the following disclaimer, which might frustrate clinicians who are looking for firm guidance: "The USPSTF recognises that clinical decisions involve more considerations than evidence alone. Clinicians should understand the evidence but individualize decision making to the specific patient or situation."
When patients request PSA tests or initiate discussions about the new recommendation against screening, clinicians obviously will need to take a position one way or the other. But what about men who don't bring up the issue? For example, should clinicians who agree with the "D" recommendation still mention the PSA test — if only to tell the patient why they discourage screening?
The American Society of Clinical Oncology has also issued what it calls a "provisional clinical opinion" on PSA screening for prostate cancer that is at odds with guidelines issued in May by the USPSTF.
ASCO recommends against screening men with a life expectancy of 10 years or less "because harms seem to outweigh potential benefits." For those with a life expectancy of more than 10 years, ASCO recommends a discussion between physicians and patients about the appropriateness of PSA screening — a discussion that should include information about the possible harms associated with a positive screen.
The USPSTF flatly recommends against routine PSA screening.
A recent study evaluates trends in prostate cancer incidence following the release of the 2008 USPSTF recommendation. If the revised recommendation led to a decline in prostate cancer screening rates, there should have been a corresponding decline in the incidence of early-stage tumours among men 75 and older relative to trends in the incidence of late-stage tumors and early-stage tumours in younger men.
The study measured trends in prostate cancer incidence rates by age group covering 28% of the U.S. population. Patients were grouped into three age categories (30-64 years, 65-74 years, and 75 years and older).
There were 254,184 prostate cancer cases. There were 198,417 early-stage cases, 34,695 late-stage cases, and 21,072 cases of unknown stage. There were 109,053 cases (all stages) among men aged 30 to 64 years, 91,868 cases among men aged 65 to 74 years, and 53,263 cases among men 75 years and older.
There wass a sudden decrease in the incidence of early-stage tumors among men 75 and older after the release of the revised USPSTF recommendation.
Between 2007 and 2009, the adjusted incidence rate for early-stage tumours among men 75 years and older decreased from 443 to 330 per 100,000. The absolute number of cases declined from 8137 to 6162. The incidence of late-stage tumours decreased from 83 to 71, and the incidence of tumours with unknown stage decreased from 124 to 103. The incidence of early-stage tumors among men aged 65 to 74 years decreased from 697 to 591 . The incidence of early-stage tumours among men aged 30 to 64 years decreased from 105 to 93.
There was an immediate decline in the incidence of early-stage prostate cancer tumours among men 75 years and older after the USPSTF recommended against screening this group. The magnitude of the decline was larger than the secular decline in the incidence rate for other stage and age groups. The results are consistent with the hypothesis that the revision of the USPSTF recommendations led to a small to moderate decline in prostate cancer screening rates. Many men 75 years and older may continue to receive screening tests. Some of the decline in the incidence of late-stage tumours may be attributable to decreases in screening via digital rectal examinations.
It may just be that doing less is actually doing more for our patients when it comes to the case of PSA testing.