A new study gives encouraging signs that a hormonal drug used to fight breast cancer might help prevent abnormal prostate growths (search) from turning into cancers.
Men who took low doses of the drug toremifene (search) for a year cut their chances of developing prostate cancer (search) roughly in half, doctors reported Saturday at meeting of the American Society of Clinical Oncology.
The findings need to be tested in larger studies, specialists say. But this is the first time any drug has been shown to prevent a precancerous condition from forming a tumor.
As many as 50,000 men each year are diagnosed with such growths, and then suffer constant worry and frequent biopsies to see whether cancer has developed.
"Before, we had nothing to offer them. Now you may have something," said Dr. Len Lichtenfeld, deputy medical director of the American Cancer Society, which had no role in the research.
Toremifene is sold as Acapodene (search) for treating advanced breast cancer. It selectively blocks some of the effects of estrogen, a hormone men have but in much smaller quantities than women.
For decades, prostate cancer prevention and treatment has focused on blocking the male hormone, testosterone. Targeting estrogen "opens up a new area," said the cancer society's medical director, Dr. Harmon Eyre.
Prostate cancer is the most common major cancer in the United States. More than 230,000 new cases and about 30,000 deaths from it are expected this year.
Men who have abnormal growths called prostatic intraepithelial neoplasia (search), or PIN, have about a 30 percent chance of developing prostate cancer within a year and about a 65 percent chance within two years.
"This is a significantly worse prognosis than, say, patients with just an elevated PSA," a blood protein used to measure prostate cancer risk, said Dr. David Price, a Shreveport, La., urologist who led the study. He consults for Memphis-based GTx Inc., which sells toremifene and paid for the study.
It involved 514 men with the growths at 64 sites across the country who were given either fake pills or 20, 40 or 60 milligrams of toremifene for a year. Biopsies were done at six months and a year after treatment started.
Cancer rates were similar among the groups at six months, possibly because initial biopsies had missed some cases that were found the second time around.
But after a year, 24.4 percent of those on the drug had developed cancer versus 31 percent of those on fake pills.
That means that for every 100 patients who took the drug for a year, seven cancers were prevented, Price said. The benefit was greatest for those who took the lowest dose for a full year. Their cancer risk was 48 percent lower than men who didn't get the drug.
Side effects were similar for those on the drug and those given fake pills: 1 to 4 percent reported headaches, hot flashes, fatigue, nausea, dry eye or problems with sex.
A larger study testing the lowest dose is enrolling 1,500 men now. If it confirms that the drug can prevent prostate cancer, it would be "an important step" because there's little agreement now about how to treat the disease once it's found, said Dr. Peter Greenwald, director of cancer prevention at the National Cancer Institute.
Two years ago, a huge study showed that a testosterone-blocking drug called finasteride (search) cut the risk of developing prostate cancer by 25 percent in men at high risk of the disease because of family history or other factors. Toremifene would be the first drug to prevent progression to cancer once abnormalities had appeared.
Also at the conference, three studies added to evidence that cholesterol-lowering statin drugs like Lipitor and Pravachol may help prevent various cancers.
Researchers looked at medical records for 1.4 million patients treated at 10 Veterans Affairs centers in Louisiana, Mississippi, Texas and Arkansas, and found that those taking statins had rates of breast, prostate and lung cancer that were 51 percent, 54 percent and 48 percent lower, respectively, than those who hadn't taken such drugs.
These are the largest studies on statin use and cancer risk in the United States. Other studies from Europe and Israel reported similar results.
In lab experiments, statins curb cell growth and tumor invasiveness, "so there's at least a logic to why they should work" against cancer, said Dr. Barnett Kramer, associate director for disease prevention at the National Institutes of Health.
However, this needs to be tested in big experiments that give statins to some and not to others, and watch to see how many cancers develop, he said.