September 6, 2007 — Screening at increased intervals does not reduce the detection of interval prostate cancers, researchers report. According to a study published online in the August 28 Advance Access issue and the September 5 print issue of the Journal of the National Cancer Institute, a larger number of prostate cancers were identified in patients who were screened every 2 years as opposed to those screened every 4 years, but more frequent screenings did not decrease the number of aggressive cancers detected.
In an accompanying editorial, E. David Crawford, MD, of the University of Colorado Health Sciences Center in Aurora, points out that a great deal of controversy surrounds screening for prostate cancer. Some medical organizations support it, and others are skeptical, he writes, and while many believe that early detection saves lives, definitive evidence is lacking.
"These controversies led to the development of a large randomized clinical trial in the United States to determine the value, if any, of early detection of prostate cancer: the Prostate, Lung, Colorectal, and Ovarian Cancer (PLCO) trial," notes Dr. Crawford. While more than 154,000 men and women have enrolled in this trial to date, there is still no definitive answer as to the value of screening for prostate cancer.
Numerous publications are arising from both the PLCO and the large European Randomized study of Screening for Prostate Cancer (ERSPC), which supplied the data for the current study, Dr. Crawford writes. "The ultimate publications from these trials will be to define the value of early detection."
The incidence of prostate cancer has risen substantially during the past 2 decades, coinciding with the introduction of the prostate-specific antigen (PSA) screening test. Scientific evidence is lacking, write the researchers, that supports the efficacy of PSA screening in regards to preventing prostate cancer–related mortality and about whether mass screening of clinically asymptomatic men outweighs the loss of quality of life caused by overdetection and overtreatment.
Monique J. Roobol, PhD, of Erasmus Medical Centre in Rotterdam, the Netherlands, and colleagues, evaluated if screening for prostate cancer every 2 years, vs every 4 years, would increase the detection of interval prostate cancers. They analyzed data from the ERSPC, which was begun in 1993 to either support or exclude the effect of screening on prostate cancer mortality.
Study participants received screening at either of 2 centers; 13,301 men were screened every 4 years at the Rotterdam center, whereas 4202 men were screened every 2 years at the Gothenburg center. The researchers then analyzed the potential differences between the 2 centers as far as overall rate of prostate cancer, interval cancers, and aggressive interval cancers up to 10 years after the patients had received their initial screening.
At follow-up, 57 (0.43%) men screened every 4 years were diagnosed with interval cancer, and, of this group, 15 (0.11%) had an aggressive tumor. In the 2-year screening group, 31 (0.74%) patients were diagnosed with interval cancer, and 5 (0.12%) were diagnosed with aggressive disease.
Overall, they found that the 10-year cumulative incidence for all prostate cancers in the Rotterdam group was 1118 (8.41%) as compared with 552 (13.14%) for the Gothenburg group. But even though a higher rate of cancers was detected in the center that screened every 2 years, the 2-year interval did not decrease the detection of interval prostate cancers, the researchers observe. This difference in the number of interval cancers and the number of aggressive interval cancers between the 2 centers did not reach statistical significance.
"Provided that PSA testing is ultimately shown to reduce prostate cancer mortality, the future goal should be to evaluate and individualize the screening interval and the age when screening should be offered to obtain an optimal balance between a favorable stage distribution and risk of overdiagnosis," they write. "With the present results, it does not seem justified to recommend annual PSA testing except in men at high risk of prostate cancer, who may be identifiable at secondary screening using recently developed algorithms."
The study was funded by the Dutch Cancer Society; the Netherlands Organization for Health Research and Development; 6th Framework Program of the EU; The Swedish Cancer Society; Wallac Oy; Hybritech Inc; Schering Plough, Sweden; and Abbott Pharmaceuticals, Sweden.
J Natl Cancer Inst. Published online August 28, 2007.
2007;99:1279-1280, 1296-1303.
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