ORLANDO, Fla. — A drug now used to treat breast cancer might be able to prevent prostate cancer in men with a precancerous condition, doctors said yesterday. Another study suggested that the widely used cholesterol-lowering drugs called statins might stave off breast cancer.

But experts cautioned that more studies were needed before the drugs were prescribed to prevent prostate and breast cancer.

"We are not ready to recommend statins for those patients who do not have lipid abnormalities," said Dr. Vikas Khurana of Louisiana State University, an author of the statin study, referring to people with high cholesterol.

The findings were discussed at the annual meeting of the American Society of Clinical Oncology, a group of cancer specialists. The group, dedicated mainly to treating cancer, has acknowledged recently that preventing cancer could be every bit as important.

The statin study analyzed medical records of 40,000 women in the database of the Veterans Affairs medical system. It found that women who used statins were half as likely to develop breast cancer as those who did not. But such studies looking back at medical records are not as reliable as clinical trials.

The prostate-cancer study was a random clinical trial involving 514 men with precancerous lesions analogous to polyps for colon cancer. The condition is called prostate intraepithelial neoplasia, or PIN.

No effective treatment exists for the problem, diagnosed only by a pathologist who examines prostate tissue removed in a biopsy. Men who have it are advised to undergo periodic blood tests and biopsies.

In the study, 24.4 percent of those men who received a once-a-day tablet of toremifene developed prostate cancer after one year, fewer than the 31.2 percent of those who were given a placebo.

Toremifene is a breast-cancer drug similar to tamoxifen in that it blocks the action of the hormone estrogen.

Prostate-cancer growth is fueled by the hormone testosterone, and many treatments for the disease block that hormone. But those treatments, effectively chemical castration, cause loss of libido and other side effects.

There is evidence that estrogen, normally thought of as the female hormone, also helps fuel prostate-cancer growth. Dr. Mitchell Steiner, professor of urology at the University of Tennessee, theorized that blocking estrogen might provide a treatment or preventative with fewer side effects.

So Steiner started a company, GTx, with financial backing from one of his patients, J.R. Hyde III, founder of the AutoZone chain of car-parts stores. The company, based in Memphis, Tenn., has the rights to toremifene and financed the clinical trial.

Dr. Peter Scardino, chief of urology at Memorial Sloan-Kettering Cancer Center in Manhattan, said the study was well-designed and the findings surprising, but that confirmatory studies were needed.

"We are approaching a time when chemo-prevention with hormonal manipulations that are not equivalent of full castration will be feasible," Scardino said.

One mystery that needs explaining, he said, is that in the trial the lowest dose of drug worked best. Two higher doses did not produce a statistically meaningful reduction in cancer risk.

In the trial, side effects seemed small, doctors said. To win approval of the drug, the company has begun a larger study in which 1,500 men will be followed for at least two years.

The breast-cancer study involved female veterans at 10 VA centers in four states. The study compared statin use among 556 women with a history of breast cancer and among 39,865 who did not have the disease.

After statistically controlling for a number of factors such as age, smoking and diabetes, researchers found a 51 percent lower risk of breast cancer among statin users, Khurana said.

There have been several studies suggesting that statins might prevent cancer, but other studies have shown no effect. The studies are "all over the board," said Dr. Barnett Kramer of the Office of Disease Prevention at the National Institutes of Health.

Dr. Robert Mayer of the Dana-Farber Cancer Institute in Boston said it was time for a company or the government to sponsor a forward-looking clinical trial that could answer the question more definitely than can tantalizing but inconclusive studies that look back at medical records.

"I think we do need to move the statins to a fish-or-cut-bait situation," Mayer said.

Another study of medical records suggested that the drug raloxifene might lower the risk of endometrial cancer, a disease of the lining of the uterus, while confirming previous studies that tamoxifen might raise the risk.

Raloxifene, sold by Eli Lilly as Evista, is approved for osteoporosis. But a trial is under way testing it against tamoxifen for breast-cancer prevention.

Also at the conference, a new study found that the drug gemcitabine can reduce the recurrence of pancreatic cancer when used after surgery to remove a tumor. The drug, sold as Gemzar by Eli Lilly, now is approved for treating pancreatic cancer after surgery is no longer possible.

But the finding might apply to only about 20 percent of patients, since most cases of pancreatic cancer are diagnosed after it is too late for surgery, said Dr. Michael Arning, medical director for the drug at Lilly.