CHICAGO--DNA ploidy in needle biopsy specimens is proving to be a highly accurate method of predicting local and distant spread of prostate cancer, as well as the probability of recurrence, Matthew Rifkin, MD, reported at the annual meeting of the Radiological Society of North America.

As a result, he said, clinicians should be able to use DNA ploidy analysis of needle biopsy specimens to tailor treatment to the aggressiveness of the cancer and avoid unnecessary surgery.

"One of the challenges when deciding how to treat cancer is knowing whether or not you're dealing with a cancer that is likely to spread or recur. If prostate cancer is not likely to recur, it doesn't make much sense to subject men to surgery and its potential side effects, such as impotence or urinary incontinence," said Dr. Rifkin, professor and chairman, Department of Radiology, Albany Medical College, New York.

A full assessment of the prostate cancer typically has had to wait until a specimen of tissue was obtained at surgery because an accurate histologic grade of the tumor could not be determined from biopsy samples. The accuracy of the histologic assessment of a biopsy specimen has been suspect because the small-gauge biopsy needles were thought to cause fragmentation of tumor cells.

DNA information, however, is preserved in biopsy specimens, and a study by Dr. Jeffrey Ross, chairman of pathology, Albany Medical College, along with Dr. Rifkin, shows that DNA analysis of needle biopsy specimens is just as accurate as the histologic evaluation of radical prostatectomy specimens in predicting the course of prostate cancer.

Needle biopsy specimens were obtained from nearly 100 men with prostate cancer who were followed for 4 to 5 years. The biopsy specimens were compared with radical prostatectomy specimens for DNA ploidy analysis. Such analysis determines the extent of multiple sets of chromosomes in a sample of cells. It characterizes DNA patterns as diploid, which has the usual two sets of chromosomes, or aneuploid, which has a different number of sets of chromosomes.

Aneuploidy in either the biopsy samples or the surgical specimens was the best indicator of the probability of cancer migration or recurrence, Dr. Rifkin said. The rate of cancer spread beyond the prostatic capsule or recurrent tumor was three to four times higher in aneuploid tumors than in diploid tumors.

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