May 23, 2012
Prostate-Cancer Screenings Unnecessary - Lead To Dangerous Treatments
The uproar that began last year when the U.S. Preventive Services Task Force stated that doctors should no longer offer regular prostate-cancer tests to healthy men continued this week when the task force released their final report. Overall, they stuck to their guns, stating that a blood test commonly used to screen for prostate cancer, the PSA test, causes more harm than good -- it leads men to receive unnecessary, and sometimes even dangerous, treatments.
Some practitioners are refusing to believe the failure of PSA tests even with overwhelming evidence, such as a ten-year study of around 250,000 men that showed the test didn't save lives, many activists and medical professionals are clamoring for men to continue receiving their annual PSA test. Why the disconnect?
In an article published in Psychological Science, a publication of the Association for Psychological Science, researchers Hal R. Arkes, of Ohio State University, and Wolfgang Gaismaier, from the Max Planck Institute for Human Development in Berlin, Germany, picked apart laypeople's reactions to the report, and examined the reasons why people are so reluctant to give up the PSA test.
"Many folks who had a PSA test and think that it saved their life are infuriated that the Task Force seems to be so negative about the test," said Arkes.
The test according to one study missed 82 percent of tumors in men under 60. Dr. Rinaa Punglia of Harvard Medical School and her team said the accuracy of the test has been overrated because doctors do not routinely confirm what seems to be a healthy reading on the test.
A PSA blood test looks for prostate-specific antigen, a protein produced by the prostate gland. High levels are supposedly associated with prostate cancer. The problem is that the association isn't always correct, and when it is, the prostate cancer isn't necessarily deadly. Nearly 20 percent of men will be diagnosed with prostate cancer, which sounds scary, but only about 3 percent of all men die from it. The PSA test usually leads to overdiagnosis -- biopsies and treatment in which the side effects are impotence and incontinence. Moreover, there is some evidence which suggests that biopsies and treatment actually aggravate prostate cancer. During a needle biopsy, a tumor may need to be punctured several times to retrieve an amount of tissue that's adequate enough to be screened. It is believed that this repeated penetration may spread cancer cells into the track formed by the needle, or by spilling cancerous cells directly into the bloodstream or lympathic system.
For every 100 men over the age of 50 who have the PSA test :
- About 90 will have a normal PSA level, and about 10 will have a higher than normal level.
- These 10 men will then need to go through other tests and examinations. At the end of these tests :
- Three men (3/10) will be found to have significant prostate cancer after the first biopsy, however spontaneous remission is common and never recorded; i.e., seven men (7/10) will be found not to have prostate cancer at this time (false positives);
- Over the next several years, another two of these men will have significant prostate cancer detected during follow-up;
- Over an extended period of time, five of the ten men will be found not to have prostate cancer despite further investigation (false positives).
- One or two of the 90 men who had a normal PSA test will actually have prostate cancer that is clinically significant and will cause symptoms at a later date (false negatives).
Very high PSA levels usually occur in men with advanced or metastatic prostate cancer, but such high levels are rarely seen in men with early disease.
They suggest several factors that may have contributed to the public's condemnation of the report. Many studies have shown that anecdotes have power over a person's perceptions of medical treatments. For example, a person can be shown statistics that Treatment A works less frequently than Treatment B, but if they read anecdotes (such as comments on a website) by other patients who had success with Treatment B, they'll be more likely to pick Treatment B. The source of the anecdotes matters too. If a friend, a close relative, or any trusted source received successful treatment, they would be more likely to recommend that treatment to others, even if there was evidence showing the treatment only works for a minority of people.
Arkes and Gaismaier also propose that the public may have recoiled against the task force's recommendations so fiercely because they weren't able to properly evaluate the data in the report. Confusion over the use of control groups may have led people in the general public to weigh the data differently than medical professionals did.
April McCarthy is a community journalist playing an active role reporting and analyzing world events to advance our health and eco-friendly initiatives.