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Feb. 15, 2008 (San Francisco) -- A biopsy reveals more important information about a man's prostate cancer than previously understood, a new study shows.
Other research suggests that a genetic test can help to spare thousands of men from the discomfort and misery of unnecessary biopsies.
Both studies were presented here at the 2008 Genitourinary Cancers Symposium, sponsored by the American Society of Clinical Oncology (ASCO) and two other cancer care organizations.
Philadelphia researchers studied more than 300 men who were undergoing radiation treatment for prostate cancer. They found that the location and amount of cancer found on a biopsy prior to treatment were predictive of whether a man would have persistent disease after treatment -- and where the cancerous cells would be located.
Currently, doctors monitor PSA levels after radiation treatment to determine if prostate cancer has come back. But PSA gives an incomplete snapshot of a patient's outlook, says Mark K. Buyyounouski, MD, attending physician in radiation oncology at Fox Chase Cancer Center.
Seeking to find a better predictor of recurrence, the researchers compared prostate biopsies taken before treatment with those taken two years after treatment. All the men had cancers that were classified as intermediate or high risk.
"What we found is that men who had bigger tumors at first biopsy were more likely to have local persistence of the disease on the same side of the prostate after treatment," Buyyounouski says.
Left untreated, locally persistent prostate cancer may result in later spread of the disease and possibly death, he says.
ASCO spokesman Eric A. Klein, MD, head of urologic oncology at Cleveland Clinic, says the information is important because it gives doctors an opportunity to tailor treatment, such as by targeting higher-dose radiation the first time around to an area that contains a large tumor.
Buyyounouski tells WebMD that the researchers plan to test that strategy in an upcoming study.
The second study involved men who did not have signs of prostate cancer on their first biopsy but were thought to be at high risk of developing the disease because of high PSA levels, atypical, irregular cell growth, or other factors.
"While we know some of these patients will actually have cancer on the repeat biopsy, about 70% will not. So we want a test that tells you that you don't need to be re-biopsied or at least you can wait longer," says researcher Bruce J. Trock, MD, of Johns Hopkins.
The researchers studied 86 men who had a negative biopsy (no evidence of cancer on biopsy) but were at high risk of prostate cancer. About one in five proved to actually have cancer on a second biopsy.
Using tissue samples from the first biopsy, the researchers looked at the status of a gene called APC that normally protects the prostate cells from mutating and turning cancerous.
They found that if APC was not turned off, there was a 96% chance that a man would not have cancer.
If the test pans out in future research, "It will help alleviate a lot of stress for men with no cancers but high-risk features on a first biopsy," Buyyounouski says.
Biopsies are not a pleasant experience, he tells WebMD. Using a rectal probe, about 12 to 14 needles are directed into the prostate under ultrasound guidance. There's some risk of bleeding, infection, and urinary obstructions.
"It's not something you want if you can avoid it," Buyyounouski says.