July 26, 2010 -- More than 75% of men diagnosed with low-risk prostate cancer undergo aggressive treatment -- either complete removal of the prostate or radiation therapy, according to a new study.
That's true, the researchers found, even in men with a low level of prostate-specific antigen (PSA) of under 4 nanograms per milliliter, one of the factors taken into account when treatment decisions are made.
''If we knew for sure everyone with a PSA under 4 would not die of prostate cancer, case closed," says researcher Mark N. Stein, MD, a medical oncologist at The Cancer Institute of New Jersey and assistant professor of medicine at the UMDNJ-Robert Wood Johnson Medical School, New Brunswick.
But that's far from true, Stein says. And that makes the balance between overtreatment and undertreatment difficult, he says. The report is appears in the Archives of Internal Medicine.
"The tremendous improvement in survival has been attributed to early detection and treatment," Stein and his colleagues write. "However, there have been concerns about the potential overdiagnosis and overtreatment of localized prostate cancer."
In the study, they looked at data from nearly 124,000 men with newly diagnosed prostate cancer from 2004 to 2006 to determine which men received aggressive treatment.
More than 192,000 new cases of prostate cancer were diagnosed in 2009, according to the American Cancer Society, and more than 27,000 men died of it.
Stein and his team looked at data from the SEER database, which drew from 16 tumor registries and covers about 26% of the U.S. population.
In all, 14% of the men had a PSA of 4 nanograms per milliliter or lower.
The PSA test measures prostate-specific antigen, a protein produced by the prostate. Typically, the higher the PSA level, the higher the risk of prostate cancer, although some men can have an elevated PSA without cancer and some men can have cancer without an elevated PSA. Most healthy men without prostate cancer will have a PSA of less than 4 nanograms per milliliter, so that level is a general cutoff as to whether to proceed to biopsy, although some say the threshold should be lower and adjusted for age.
Fifty-four percent of the men diagnosed with prostate cancer with a PSA at 4 or lower had low-risk disease, they found. That was also defined as being at stage T2a or lower, with a Gleason score of 6 or lower. A Gleason score, Stein says, is based on "how the cancer looks under the microscope." Scores of 8-10 (10 highest possible) are high-grade tumors, according to the American Cancer Society.
More than 75% of these men with so-called low-risk disease got aggressive therapy, Stein found -- either radical prostatectomy, complete removal of the gland, or radiation therapy.
The decisions are difficult, Stein tells WebMD. "Guys with PSAs under 4 could have lethal cancers," he says.
''These results underscore the fact that PSA level, the current biomarker, is not a sufficient basis for treatment decisions," the researchers write. What's needed, Stein says, are other markers -- such as specific genetic signatures tied to higher-risk disease -- to better predict the risk of a lethal cancer.