August 12th, 2012

Study: No PSA Tests, Advanced Cancer Triples

By Charles Bankhead, Staff Writer, MedPage Today
Published: July 30, 2012
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

Action Points
Elimination of PSA testing would triple the number of men who have advanced prostate cancer at diagnosis, this study suggests.

Point out that the findings have potentially major implications in light of the recent U.S. Preventive Services Task Force (USPSTF) recommendation against routine PSA screening tests.
Elimination of PSA testing would triple the number of men who have advanced prostate cancer at diagnosis, authors of a retrospective review concluded.

Extrapolation of cases from the pre-PSA era to 2008 showed that the number of metastatic (M1) prostate cancers at diagnosis would increase from 739 to an estimated 2,277, in a review limited to a National Cancer Institute database.

Further extrapolation of cases in the database to the entire population resulted in an increase from 8,000 to 25,000 cases of M1 prostate cancer at diagnosis.

The findings have potentially major implications in light of the recent U.S. Preventive Services Task Force (USPSTF) recommendation against routine PSA screening tests, according to an article published online in Cancer.

"Our analyses suggest that, if the pre-PSA era incidence rates were present in the modern U.S. population, then the total number of men presenting with M1 prostate cancer would be approximately three times greater than the number actually observed," Edward M. Messing, MD, of the University of Rochester in New York, and co-authors wrote in conclusion.

"We believe that these estimates must be taken into consideration (bearing in mind the limitations of observational data) when public health policy-level recommendations are made regarding PSA screening."

Conflicting clinical evidence and guideline recommendations have made PSA testing a hot-button issue in U.S. healthcare policy. Three years ago, published results of two large screening studies showed different outcomes: a large European study demonstrated a survival benefit with PSA screening and a large U.S. study suggested that screening did not reduce the risk of prostate cancer mortality.

Long-term follow-up in the U.S. study confirmed the lack of a survival benefit.

Last year the USPSTF issued a conditional recommendation against PSA screening for prostate cancer as a component of routine care. Earlier this year the task force finalized the recommendation, as its panelists concluded that screening asymptomatic men had the potential to cause more harm than good.

The American Cancer Society threw its support behind the USPSTF decision, whereas the American Urological Association condemned the recommendation and reaffirmed its support for risk-guided PSA screening.

Earlier this month the American Society of Clinical Oncology issued a provisional clinical opinion that discouraged PSA screening of men with a life expectancy of less than 10 years and that encouraged individualized decision making for patients with a longer life expectancy.

Messing and colleagues sought to inform the debate by seeking evidence from a different perspective. Specifically, they examined the age- and race-specific annual incidence of M1 prostate cancer at diagnosis in the era before PSA testing became widely available and compare the rates with those in the most recent years of the PSA era.

The investigators also estimated the number of men who would be expected to have M1 prostate cancer at diagnosis in the current era if PSA testing were not available. For purposes of their calculations, they defined the pre-PSA era as 1983 to 1985.

Examination of the current era consisted of data from participating registries in the Surveillance, Epidemiology, and End Results (SEER) program for 2008, the most recent year with complete data.

Analysis of the SEER data showed that 739 men had M1 prostate cancer at diagnosis in 2008. On the basis of diagnoses in the period from 1983 to 1985, the number of M1 cases would have increased to 2,277 had PSA testing not been available in 2008, an expected-to-observed ratio of 3.1 (95% CI 3.0 to 3.2).

Applying the ratio to the general population, Messing and colleagues estimated that 25,000 men would have had M1 disease at diagnosis in 2008 in the absence of PSA testing. In contrast, the observed number of M1 cases at diagnosis in 2008 was 8,000.

The results also have relevance for several recent studies suggesting that PSA screening can be safely stopped after age 75.

"We observed that, for both races, the apparent benefit of screening in terms of the absolute reduction in the risk of presenting with M1 prostate cancer increased with age," the authors wrote. "In particular, differences in the rates during the pre-PSA era and the PSA era in presenting with M1 prostate cancer increased with age until age 85 years."