June 4, 2007 A researcher in the Oregon Health & Science University Cancer Institute and Portland Veterans Affairs Medical Center has found a way to identify which men need a second prostate biopsy because they may be harboring life-threatening prostate cancer even though they were given a clean bill of health after their first biopsy.
Shane Rogosin, M.D., principal investigator, resident, in general internal medicine, OHSU School of Medicine, presented the research on Saturday, June 2 at the 43rd annual meeting of the American Society of Clinical Oncologists in Chicago.
Also involved in the research is Mark Garzotto, M.D., h the director of urologic oncology at the Portland Veterans Affairs Medical Center, assistant professor of surgery (urology) in the OHSU School of Medicine, and member of the OHSU Cancer Institute.
"Until now we've really had no clear and consistent method to recommend further follow up or diagnostic procedures for men who have a negative biopsy. We have derived a simple marker so urologists can identify who is at risk for high-grade prostate cancer," Garzotto said.
Rogosin studied what is considered a large group, 511 subjects at the Portland Veterans Affairs Medical Center from 1992 to 2006. All had been referred to urology clinics for suspicion of prostate cancer. All patients had one prior negative prostate biopsy. In all, the study included 1,319 biopsies.
What the researchers found to be the indicator for a repeat biopsy was a high prostate specific antigen (PSA) adjusted for prostate size. A Gleason score of 7 or above was indicative that life-threatening prostate cancer may be present and a repeat biopsy is advised.
A Gleason score is a system of grading prostate cancer tissue based on how it looks under a microscope. Gleason scores range from 2 to 10 and indicate how likely it is that a tumor will spread. A low Gleason score means the cancer tissue is similar to normal prostate tissue and the cancer is less likely to spread; a high Gleason score means the cancer tissue is very different from normal tissue and the tumor is more likely to spread. A high grade of cancer results in a higher PSA. Garzotto also stresses the size of the prostate has to be taken into account when measuring PSA.
"What we worry about is which men may have high-grade cancer. Now we can prescribe a second biopsy for a few months later. We know that this is a judicious use for a biopsy," Garzotto said. Besides identifying which men may have a deadly form of prostate cancer this new finding could also reduce the rate of overtreatment, unnecessary biopsies and overdiagnosis.
Prostate biopsies can cause patient anxiety, pain, bleeding and infection, and can lead to a significant increase in medical and non-medical costs to health care systems and patients.
This study is particularly meaningful because of the large sample size of patient cases, and it is longitudinal, which means researchers were able to study the patients for many years.
Prostate cancer is the most common cancer, excluding skin cancer, and the second leading cause of cancer-related death in men in the United States. It is estimated that there will be 218,890 new cases diagnosed in 2007, and 27,050 men will die from prostate cancer this year in the United States.
More than 1 million prostate biopsies are performed each year. Of those, only about 25 percent test positive for cancer. However, another 25 percent are given a false negative, meaning that no cancer is detected even when later it is found that the patient does have cancer.
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