Wednesday, July 28, 2010

Is treatment too aggressive for men with low-risk prostate cancer?

The prostate specific antigen test measures levels of particular
protein in the blood that is a biomarker for prostate cancer.
(Photo courtesy of the Harding Center for Risk Literacy) 
CHICAGO – Most men with low-risk prostate cancer are undergoing aggressive surgeries and radiation therapies despite the significant risk of impotence, and loss of bladder and bowel control, that such treatments carry, a new study shows.

Led by Dr. Yu-Hsuan Shao, Ph.D., of the Cancer Institute of New Jersey, researchers analyzed data from the National Cancer Institute’s Surveillance, Epidemiology and End Results System. They found that 44 percent of men with prostate specific antigen (PSA) levels of less than 4.0 nanograms per milliliter (ng/ml) and 38 percent of those with a PSA between 4.1 ng/ml and 10.0 ng/ml underwent radical prostatectomy, which removes the prostate and nearby lymph nodes.

Similarly 33 percent of men with PSAs of 4.0 ng/ml or less and another 40 percent of men with PSAs between 4.1 ng/ml and 10.0 ng/ml underwent radiation therapy.

"Despite their lower risk of having clinically significant disease, treatment rates for men with PSA values of 4.0 ng/ml or lower were comparable to those of men presenting with PSA values between 4.0 and 20.0 nanograms per milliliter," the authors wrote.

In the study the researchers analyzed data taken from 123,934 men with newly diagnosed prostate cancer from 2004 to 2006. They found that 14 percent had PSA levels of 4 nanograms per milliliter or lower, which is in the high-end of the normal range for PSA levels and the threshold for deciding whether or not to undergo a biopsy to confirm prostate cancer. Even if found, half of the cancers found in these men are considered low-risk and not likely to pose a clinical threat.

More than 90 percent of all prostate cancers are diagnosed before the disease has spread to other parts of the body, and the five-year survival rate for these patients diagnosed with localized disease is almost 100 percent, according to background information in the article. Since 1975, before the PSA test was introduced, the five-year survival rate from all stages of disease has increased from 69 percent to almost 99 percent in 2003.

"The tremendous improvement in survival has been attributed to early detection and treatment," the authors write. "However, there have been concerns about the potential over diagnosis and over treatment of localized prostate cancer. Despite these concerns, some researchers argue that the prostate-specific antigen (PSA) level is associated with a continuum of cancer risk and recommend lowering the 4-ng/ml threshold for biopsy."

In the study, Shao’s team showed that, based on their study results, if the PSA threshold for biopsy were lowered, the effect would result in 1.9 million more men diagnosed with low-risk prostate cancer and 1.5 million (82.5 percent) would receive aggressive treatment aimed at curing the cancer despite statistics showing that only 2.4 percent of them would have high-grade cancer.

SOURCE: press materials provided by the Archives of Internal Medicine re.: (Arch Intern Med. 2010;170[14]:1256-1261

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