CME Released: 09/20/2010; Valid for credit through 09/20/2011
September 20, 2010 — Men with low baseline serum prostate-specific antigen (PSA) values are not likely to benefit from further prostate cancer screening and can therefore forgo it, suggests a new European study.
This provocative observation needs to be solidified with longer follow-up, admit the study authors, led by Pim J. van Leeuwen, MD, from Erasmus Medical Center in Rotterdam, the Netherlands. They also say that their study methods might have biased their outcomes.
Dr. van Leeuwen and his coauthors were all involved in the European Randomized Study of Screening for Prostate Cancer (ERSPC), and they used data from that landmark study in their new analysis, which was published online September 13 in Cancer.
The new study, which had about 9 years of follow-up data on the men, found that the "greatest benefits of early detection programs may be" when baseline PSA values are relatively high (in the range of 4.0 to 9.9 ng/mL or 10.0 to 19.9 ng/mL).
For instance, the authors found that for men with PSA levels between 10 and 19.9 ng/mL, 133 men would need to be screened to prevent 1 death from prostate cancer.
However, for men with low PSA levels (between 0.0 and 1.9 ng/mL), the benefits of screening and treatment were much less favorable: 24,642 men would need to be screened and 724 cases of prostate cancer would need to be treated to prevent 1 disease-related death.
"Current analyses suggest that the significant reduction in disease-specific mortality with screening and early detection may be limited to men with baseline elevated PSA levels," conclude the study authors.
Furthermore, the authors say that the "benefits of continued aggressive investigation and treatment may be limited" in men with low baseline PSA levels.
However, an American prostate cancer screening expert said that this study is "not a game changer."
Andrew Wolf, MD, associate professor of medicine at the University of Virginia School of Medicine in Charlottesville, agreed with the study authors' critique of their methods and said the findings have to be taken with a "huge grain of salt."
Apples and Oranges
The study authors set out to determine whether baseline PSA values indicate just how the harms and benefits of prostate cancer screening are distributed among men who undergo the screening.
The question is crucial because it is now clear that prostate cancer screening reduces prostate-cancer-related deaths but still requires a multitude of men to be overtreated, say the study authors.
In short, it's good to know that PSA-based screening works, but it would be better to know in which men it works best, they suggest.
To address the issue, the authors turned to data from the ERSPC, which showed a 20% reduction in prostate cancer mortality among screened men, compared with unscreened control subjects.
Their "intervention" population consisted of 43,987 men 55 to 74 years of age who were enrolled between 1993 and 1999 and who were randomized to the intervention or screening group of the ERSPC.
However, the unscreened control subjects in the ERSPC study, which was conducted in the Netherlands, Sweden, and Finland, never underwent PSA testing and therefore had no baseline PSA values.
Thus, the investigators lacked a "clinical" population of men with PSA values to compare with their intervention screening population.
To remedy the situation, they turned to a database of 42,503 men in the same age range from Northern Ireland who had their PSA levels measured between 1994 and 1999. The data are from the Northern Ireland Cancer Registry, which contains the results of all PSA tests done in the country.
Herein lies a problem, suggested Dr. Wolf, who was the lead author of the American Cancer Society's recent revision of their prostate cancer screening guidelines and was asked by Medscape Medical News to comment on the study.
"They're comparing apples and oranges," he said.
The 2 populations — from the ERSPC and from Northern Ireland — had significant differences, he said. Most notably, the overall mortality was 25% in the clinical group and 14% in the screening group. "The men from Northern Ireland were clearly a sicker population," explained Dr. Wolf.
There are other differences, he continued, citing the significantly higher median baseline PSA value among the men from Northern Ireland.
The study authors adjusted their analyses of the data to account for the various differences, but Dr. Wolf thinks it was in vain.
"I don't think you can adjust enough to make them comparable populations," he said, which weakens the study conclusions.
The study authors believe that with more follow-up their study might be more valuable. Again, Dr. Wolf is doubtful. "It's hard to draw firm conclusions because of the different populations, even with more follow-up."
In the Netherlands, the ERSPC is supported by grants from the Dutch Cancer Society, the Netherlands Organization for Health Research and Development, Beckman Coulter Hybritech Inc, and Europe Against Cancer. In Sweden, the ERSPC is supported by the Swedish Cancer Society, Wallach Oy Hybritech Inc, Schering-Plough Sweden, and Abbott Pharmaceuticals Sweden. In Finland, the ERSPC is supported by the Academy of Finland, the Cancer Society of Finland, the Sigrid Juselius Foundation, the Competitive Research Funding of the Pirkanmaa Hospital District, Doctoral Programs in Public Health, the Helsingin Sanomat Centenarian Fund, Hybritech Corporation, and the Foundation for Finnish Culture.
The authors have disclosed no relevant financial relationships.
Cancer. Published online September 13, 2010.
sumber : http://cme.medscape.com/viewarticle/728965?src=cmemp&uac=97984HK
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