PSA Tests Cut Risk of Prostate Cancer Spread
Study Shows Benefits of Prostate Cancer Screening in Avoiding the Disease’s Spread to Other Organs
Oct. 25, 2010 -- Routine PSA testing substantially lowers the chance that prostate cancer will spread to other parts of the body, researchers report.
Once the disease spreads, it is no longer curable, says study head Chandana Reddy, MS, a senior biostatistician at the Cleveland Clinic.
Additionally, men whose cancer metastasizes (spreads) are typically given long-term hormone therapy, which carries a host of side effects, including weight gain, fatigue, loss of libido, and an increased risk of heart disease, she tells WebMD.
"Based on the results, we feel patients should be screened," says co-investigator Jay Ciezki, MD, also of the Cleveland Clinic. "Screening decreases the metastatic disease burden, so patients suffer less and their quality of life is better."
The findings were released at a news briefing held in advance of the annual meeting of the American Society for Radiation Oncology in San Diego (ASTRO) next week.
Controversy Over Prostate Cancer Screening
To screen or not to screen for prostate cancer is one of the biggest controversies in medicine today, says Harvard Medical School's Anthony Zietman, MD, president of ASTRO.
The $30 to $50 blood test measures the level of prostate specific antigen (PSA), a protein produced by the prostate. Increased levels of PSA may be a sign of prostate cancer.
Because most prostate tumors are so slow-growing that men will die of other causes long before they become lethal, many experts believe routine PSA testing leads to "much overdiagnosis of cancers that don't need to be fixed," Zietman tells WebMD.
Additionally, some studies suggest screening does not extend lives.
The Cleveland Clinic team discounted survival rates as the best measure of the effectiveness of PSA testing. "What's really important is whether it keeps the disease from spreading, which allows men to live more productive lives," Reddy says.
The researchers examined the medical records of 1,721 prostate cancer patients who were treated with either radiation therapy or surgery to remove the prostate gland and surrounding tissue at the Cleveland Clinic between 1986 and 1996.
The patients were divided into two groups according to when they were treated: in the prescreening era before routine PSA screening became widespread in 1993 or in the post-screening era.
Patients were classified as having high-, intermediate-, or low-risk disease depending on their PSA levels, symptoms, and the aggressiveness of their cancer.
In the 10 years after diagnosis, cancer spread in 13% of the men.
Metastatic Prostate Cancer
Findings showed that the portion of men developing metastatic disease within 10 years of diagnosis was between 8% and 24% higher among men treated before screening became widespread, depending on their risk group.
For men in the low-risk group, the chance of being disease-free at 10 years was 98% for men in the post-screening era vs. 90% for men in the prescreening era.
For men in the intermediate-risk group, 93% of those in the post-screening era were disease-free at 10 years vs. 79% treated in the prescreening era.
For men in the high-risk group, the chance of being disease-free at 10 years was 82% for men in the post-screening era vs. 58% for men in the pre-screening era.
"Any survival benefit associated with PSA screening may be masked by other diseases these men have. Measuring the risk of metastases is a better endpoint," Ciezki says.
"Early detection may not necessarily save lives, but may allow patients to live better lives," Zietman says.
This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.