Reduced prostate screening could miss advanced tumors

Relaxed guidelines on prostate cancer screening may delay diagnosis and treatment of aggressive tumors, a new study suggests.

In 2011, the U.S. Preventive Services Task Force recommended against routine prostate specific antigen (PSA) testing, to curb over-diagnosis and overtreatment of prostate cancer. Since then, PSA screening has dropped by 28 percent, the researchers report.

"On the positive side, there is a lot of prostate cancer that we don't need to know about," said lead researcher Dr. Daniel Barocas, an assistant professor of urologic surgery at Vanderbilt University, in Nashville, Tenn.

These are low-risk cancers that most men will not die of, and the treatment can be more harmful than the cancer, he explained. "To that extent, the guideline had a beneficial effect," Barocas said.

"On the negative side, we seem to be missing intermediate and high-risk cancers in men who would be eligible for treatment," he said. "Those are missed opportunities to identify disease and treat it."

The report will be published in the December issue of the Journal of Urology.

Dr. Kirsten Bibbins-Domingo, vice chair of the U.S. Preventive Services Task Force, said, "When the task force reviewed the evidence on PSA screening for prostate cancer in 2011, what we found is that there is a very small potential benefit and significant potential harms."

Most prostate cancers found by PSA screening are slow-growing and not life-threatening, she explained. "However, there is currently no way to determine which cancers are likely to threaten a man's health and which will not," she said.

Barocas disagreed.

"The policy of screening no one is throwing the baby out with the bathwater," he said.

Some men are at high risk for prostate cancer and should be screened, he said. These include men with a family history of prostate cancer, and black men.

In addition, screening should be combined with treatment. Low-risk cancer need not be treated but watched, while high-risk cancer should be treated, Barocas said. "That's the solution," he said.

Another expert made another point.

Since 2011, when the guideline was published, new techniques, including MRI and ultrasound, have been developed that can diagnose prostate cancer more accurately and distinguish between low- and high-risk cancers. These techniques may need to be taken into account in modifying the guideline, said Dr. Anthony D'Amico, chief of genitourinary radiation oncology at Brigham and Women's Hospital and Dana-Farber Cancer Institute in Boston.

Using the U.S. National Cancer Database, Barocas and colleagues looked at the effect of the new guidelines on the number of new prostate cancer diagnoses between January 2010 and December 2012.

The researchers found that the number of prostate cancer diagnoses dropped more than 12 percent (1,363 cases) in the month after the draft guideline was issued. It continued to drop to an overall decline of 28 percent in the year after the draft guideline was issued.

The diagnoses of low, intermediate and high-risk prostate cancers all decreased significantly, but diagnoses of prostate cancer that had spread beyond the prostate did not change, they found. The decreases were similar for all ages, races, income and insurance.

In the year after the guidelines were published, diagnoses of new low-risk cancers dropped nearly 38 percent and continued to fall more rapidly than diagnoses of more aggressive cancer. This suggests that for low-risk cancer, the guideline had its intended effect, Barocas said.

In addition, prostate cancer diagnoses fell by 23 percent to 29 percent among men over 70 and by 26 percent among men who were not likely to live long enough to benefit from early diagnosis and treatment, the researchers found.

However, researchers also found a drop of 28 percent in diagnoses of intermediate-risk cancer and a 23 percent drop in diagnoses of high-risk cancer one year after the guideline was published.

"These findings are consistent with what we hoped would not happen," D'Amico said.

It is likely that men will develop more advanced prostate cancer before it is diagnosed and be less likely to be cured, he added. "This is a warning that we are not picking up patients who are curable," D'Amico said.