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
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.