Prostate Size May Provide Clues in Predicting Severity of Cancer
Two recent studies have found seemingly contradictory findings about the relationship between prostate size and the likelihood of smaller glands being more likely to harbor serious disease. Both papers are published in The Journal of Urology, a publication of the American Urological Association.
Previous research has found that prostate volume increases by 14% for each decade of a man’s life. The hypothesis of a small prostate being more likely to contain more aggressive disease is based on the findings that a smaller gland has lower androgen levels. Less hormone dependent tumors tend to be more aggressive.
The first study, published by researchers from the Vanderbilt-Ingram Cancer Center, included data from 1,251 cases of prostate cancer among men who had their prostates surgically removed between January 2000 and June 2008. The patients were considered to have low-risk disease because their prostates were producing low levels of prostate-specific antigen (PSA) and they had a low Gleason score (six or less) which is a measure of the severity of cancer found during initial biopsy.
In 31% of the cases, when pathologists examined the tissue removed, the severity of cancer was upgraded from the pre-surgical analysis. Men with smaller prostates were more likely to have their cancer upgraded.
Daniel Barocas MD MPH, assistant professor of Urologic Surgery and senior study author, states that it isn’t size alone that determines the severity of disease. “What it’s really about is the ratio of PSA to size, or PSA density, meaning that a small prostate that is making a lot of PSA is likely to be due to a bad tumor, whereas a large prostate making a lot of PSA is likely to be due to benign enlargement of the prostate (BPH),” said Dr. Barocas.
But prostate size still isn’t a definitive clue and more precise tests are needed.
The second study by Stanford University School of Medicine researchers in San Jose, California involved the evaluation of 1,295 patients between 2000 and 2010 who underwent prostate needle biopsy. Of the total, 582 had prostate cancer and 398 were classified as having high grade disease. The patients were then divided by clinical T-stage which categorizes the risk of cancer spreading beyond the prostate.
Those patients with clinical T1c scores – meaning they had normal digital rectal examinations but a tumor was found in a needle biopsy because PSA was elevated – were the patients most likely to have high grade cancer. As with Dr. Barocas’ findings, Tin C. Ngo of the department of Urology at Stanford says that the characteristics of PSA influenced the findings of more severe cancer.
Dr. Barocas said the new findings provide one more piece of evidence for physicians to consider when talking with their patients. A low-risk patient, he said, would be more likely to recommend aggressive treatment if the prostate is very small because there may be a greater chance of high-grade disease.
Davies JD, Barocas DA et al. Prostate Size as a Predictor of Gleason Score Upgrading in Patients With Low Risk Prostate Cancer. The Journal of Urology December 2011 (Vol 186, Issue 6, Pages 2221-2227)
Ngo TC, Conti SL et al. Prostate Size Does Not Predict High Grade Cancer . The Journal of Urology February 2012 (Vol. 187, Issue 2, Pages 477-481)
Barocas DA, Editorial Comment. The Journal of Urology - February 2012 (Vol. 187, Issue 2, Page 481, DOI: 10.1016/j.juro.
Roehrborn CG, Prostate Size: Does It Matter? Rev Urol. 2000 Spring; 2(2): 95–98.
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