'Nerve Mapping' Helps Preserve Sexual Function After Prostate Removal

The new tool aids surgeons in pinpointing the microscopic nerves around the prostate that control sexual function, so that they can avoid damaging these nerves during prostate removal, said James Brooks, MD, an assistant professor of urology who is participating in a national, multi-center study of the device.

"It's a useful tool to help us locate those nerves and decrease the side effects of the operation. I think it has great potential for decreasing impotence after radical prostatectomy [prostate removal]," said Brooks, who practices with the Stanford Urology Clinic, part of UCSF Stanford Health Care.

The device, approved one year ago by the Food and Drug Administration, works by delivering a low-level electrical stimulus to the nerves around the prostate and then measuring the erection response. Through this process, the device helps produce a map of these critical nerves, which are invisible to the naked eye, so that doctors can navigate around them during surgery.

By simplifying an otherwise challenging surgical procedure, the new tool ultimately could make nerve-sparing surgeries much more widely available to prostate cancer patients, Brooks said.

"Doctors will be able to figure out where the nerves are, map them out and save them," he said. "So I think this will be a boon to surgery."

Men with cancers that have spread beyond the prostate are not candidates for nerve-sparing procedures, he noted.

Brooks is currently the only physician in Northern California who is using the new device, which is being evaluated on a large scale at 21 medical centers across the country. The device, called the CaverMap Surgical Aid, is made by UroMed, a biomedical company in Needham, Mass.

Vital statistics

The prostate is a walnut-sized organ that sits in a nest of blood vessels just below the bladder. Prostate cancer is the most common form of cancer among men, causing some 40,000 deaths each year in the United States. Every year, approximately 150,000 American men are newly diagnosed with the cancer. The incidence of prostate cancer has risen in the last decade, Brooks said.

Surgery is now the treatment of choice for those cancers that have not yet spread beyond the prostate. Studies have shown that men who undergo surgery have a better chance of long-term survival than those treated with other options, such as radiation, Brooks said.

But prostate surgery can also have some devastating consequences, leaving the patient impotent and/or incontinent.

That has been changing with the advent of new technologies and surgical refinements, Brooks said. The field of prostate surgery took a major leap forward in 1982, when Patrick Walsh, MD, a urologic surgeon at Johns Hopkins Medical Center in Baltimore, discovered that the nerves controlling erections do not pass through the prostate, as previously thought, but are instead situated alongside the prostate. By 1984, Walsh had developed a new technique -- called nerve-sparing radical prostatectomy -- that enabled him to preserve sexual function in a large percentage of his prostate cancer patients.

Brooks worked with Walsh for nine years before coming to Stanford a year ago.

Results vary

While many urologists now use nerve-sparing procedures, the results vary widely depending upon the skill of the surgeon, the age of the patient and other factors, according to published reports. In studies of patients undergoing such procedures, reported rates of success in preserving sexual function have ranged from 11 to 86 percent.

A newly published study from the University of Toronto suggests that doctors may get consistently good results in nerve preservation through use of the CaverMap Surgical Aid. In the study, described in the October 1998 issue of the GOLD Journal of Urology, the Toronto researchers were able to preserve potency in 16 out of 17 men, or 94 percent of patients whose prostatectomies involved use of the new tool.

At Stanford, Brooks began testing the device in September. Already, he has applied it during surgery on three patients. While Brooks said it's too soon to tell whether these men have retained erectile function, he noted that tests conducted immediately after the surgery showed that the critical nerves remained intact in each case.

Mapping procedure

The device consists of a white surgical wand with a flexible tip that delivers an electrical stimulus of up to 20 milliamps to the tissue around the prostate. A separate, fluid-filled ring that is placed around the penis can detect even the slightest erectile swelling in response to the stimulus.

The physician typically begins locating the critical nerves by placing the tip of the wand at the end of the prostate, then moving it to the middle and finally to the base of the organ. This effectively produces a map of the key nerves involved in erectile function, Brooks said.

The patient, under general anesthetic, feels nothing, he said.

After the prostate has been removed, the physician can retest the nerves to confirm that they have been spared, Brooks said. Most men take months to regain erectile function after any prostate surgery because of the trauma to the region, he noted.

Use of the nerve-finding device adds about an hour to the standard surgical procedure, for a total of about three hours, Brooks said.

Studies by others have shown that cure rates for localized prostate cancer are the same whether doctors perform a traditional surgery or use the nerve-sparing approach, he said.

Preventive efforts

While participating in the CaverMap clinical trials, Brooks is also conducting basic research on a new approach for preventing prostate cancer. He is studying specific enzymes that defend against cancer-causing toxins, in the hope that these might form the basis for a new drug or dietary agent to prevent the disease. The enzyme research is supported by a $300,000 Doris Duke Clinical Scientist Award, which Brooks received in August.

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UCSF Stanford Health Care is a private, nonprofit organization formed in November 1997 to bring together the patient-care services of Stanford University and the University of California-San Francisco.