U.S. Plans Test of Prostate Cancer Drug : Health: Nationwide research project will seek to determine if finasteride can keep healthy men from developing the often fatal disease.

The National Cancer Institute announced Wednesday that it will launch the first large-scale trial to determine whether a drug can prevent prostate cancer, the second most frequently diagnosed cancer in American men.

Researchers hope to find out whether giving finasteride--a drug already used for a non-cancerous prostate condition--to healthy men can keep them from developing the often fatal cancer.

Prostate cancer, the most common cancer in men after skin cancer, will strike an estimated 165,000 men this year and will result in 35,000 deaths in those whose cancers were discovered earlier. About 13% of American men will develop prostate cancer during their lifetimes, and 3.2% will die of the disease.

“We have a formidable problem with prostate cancer in this country,” Dr. Sam Broder, director of the cancer institute, said at a press conference. “The incidence is quite high. The death rate is unacceptable.”

The prostate is a male sex gland that produces a thick fluid that forms part of the semen, enabling sperm to be released during ejaculation. The normal prostate is about the size of a walnut, and is located below the bladder and in front of the rectum. The prostate surrounds the upper part of the urethra, the tube that empties urine from the bladder.

Age is the most significant risk factor for prostate cancer. It is rare in men younger than 45 and typically afflicts those 65 and older. Blacks have a much higher incidence than whites, while Asian immigrants have significantly lower rates.

The disease tends to run in families. Fathers and brothers of a prostate cancer patient have twice the risk of men with no relatives who have the disease. Men with three affected relatives have an elevenfold risk.

The $60-million trial will involve 18,000 men 55 and older and is expected to take a decade to complete. The men will be divided into two groups for comparison purposes, half will take the drug, the other half will receive a medically worthless placebo. Enrollment is expected to take three years and all of the men will be studied for seven years.

Finasteride is a drug commonly used to treat benign prostatic hyperplasa (BPH), a non-cancerous enlargement of the prostate gland.

Because this condition and prostate cancer are influenced by similar hormonal factors, researchers believe that the drug may also prevent cancer.

The drug controls BPH by reducing levels of the hormone dihydrotestosterone (DHT) in the prostate, blocking the activity of an enzyme that converts testosterone--the primary male hormone--to DHT.

DHT promotes the growth of prostate cancer. Thus, by using the drug to decrease levels of DHT, researchers hope to prevent the development of prostate cancer.

The trial is expected to raise questions about giving a drug to otherwise healthy individuals, as did another major prevention study launched recently by the cancer institute that involves giving the drug tamoxifen to high-risk women to try to prevent breast cancer.

But researchers insisted that the drug appears to be very safe and produces minimal side effects. Moreover, they said they believe that the potential impact of preventing prostate cancer is worth the risk.

“We feel this approach is one that makes sense,” Broder said, noting that approximately 500,000 men with BPH in 25 countries are already using the drug. Prostate cancer brings “astonishingly high costs, both economic and human,” and if the drug were to “reduce that burden,” it would have “tremendous ramifications,” he said.

The drug, manufactured by Merck & Co. Inc. of Whitehouse Station, N.J., and sold under the trade name Proscar, can cause decreased sexual desire, decreased ejaculatory volume and impotence in a small number of men.

But researchers said recent studies have indicated that these side effects frequently diminish or disappear over time in men who continue to take the drug.

The research, which will be coordinated by the Southwest Oncology Group in San Antonio, will be conducted at 222 sites in the United States, including 16 in California.

Researchers said that because risk factors for prostate cancer are not yet well defined, any man 55 or older in good health may be eligible for the study.

Volunteers will be required to undergo a digital rectal exam and a blood test for prostate-specific antigen (PSA), a protein that frequently shows elevated blood levels in men with prostate cancer. Both screenings are used to help detect prostate cancer.

Participants must show no signs of prostate cancer, meaning that the rectal exam must be normal and they must register a PSA blood level of 3.0 nanograms per milliliter of blood, or less.

About Prostate Cancer

One in 11 men will develop prostate cancer. Early detection is vital: More than 80% of those whose tumors are diagnosed early survive five years or more.

* The Prostate: It is a walnut-sized gland above the bladder. It secretes fluid that makes up part of the semen.

* Symptoms: Prostate cancer usually spreads without symptoms, making early detection by rectal examination crucial.

* Prevention: The American Cancer Society recommends that men over 40 have a rectal exam each year.

* To take part in study: Call 1-800-4-CANCER. Interested individuals must be in good health.

MOST-COMMON TYPES OF CANCER

New cases Deaths Signs/symptoms per year* per year* Breast 182,000 46,000 Lump or thickening in the breast Lung 170,000 149,000 Persistent cough Prostate 165,000 35,000 Difficulty in urinating Colon and rectum 152,000 57,000 Change in bowel habits; blood in stool

* Estimates for 1993

Sources: American Cancer Society, National Cancer Institute