SAN ANTONIO (AP) - Exercise might help women beat breast cancer. Researchers found it can ease the achy joints and muscle pain that lead many patients to quit taking medicines that treat the disease and lower the risk of a recurrence. The study is the first major test of an exercise program for women on aromatase inhibitors. These estrogen-blocking pills, sold as Femara, Aromasin and other brands, are recommended for five years after initial breast cancer treatment for hormone-driven tumors, the most common type. The pills also increasingly are being used to help prevent breast cancer in women at high risk of it because of family history, bad genes or other reasons. A separate study found that one of these medicines - anastrozole, sold as Arimidex and in generic form - cut this risk by 53 percent. It's the second aromatase inhibitor shown to lower risk that much. Despite how effective the drugs are, many women shun them because they can cause aches and pains, hot flashes and other side effects. About 15 percent of U.S. women have enough risk to merit considering the pills to prevent breast cancer, yet less than 5 percent take them, said Dr. Powel Brown, a prevention expert at the University of Texas MD Anderson Cancer Center. The exercise study involved 121 postmenopausal women taking various aromatase inhibitors to treat breast cancer who complained of achy joints on a pain survey. About half were assigned to two supervised strength training sessions a week plus at least 150 minutes of aerobic exercise per week. The rest got advice on the benefits of exercise and did their usual activities. After a year, joint pain scores fell 20 percent among exercisers and 3 percent among the others. The severity of pain and how much it interfered with daily live also declined more in exercisers. The exercise group improved cardiorespiratory fitness and lost weight - nearly 8 pounds versus a slight gain in the others. Eighty percent stuck with the program, helped by free access to a gym and a personal trainer. The National Cancer Institute paid for the study, which was led by Melinda Irwin of the Yale Cancer Center and Dr. Jennifer Ligibel of the Dana-Farber Cancer Institute in Boston. Dr. Eric Winer, breast cancer chief at Dana-Farber, said the results may help more women stick with the drugs. A lot of people will say, 'if it's going to have a lot of side effects, I'm not going to do it.' The truth is, not everyone gets symptoms. Exercise might be a solution," he said. The other study was led by Dr. Jack Cuzick of Queen Mary University of London and tested anastrozole for preventing first breast cancers. Nearly 4,000 women were given the drug or daily dummy pills, and 70 percent stuck with them for five years, just a little less than the placebo group. After that time, 40 women on anastrozole had developed breast cancer versus 85 of the others, a 53 percent reduction in risk. That's comparable to how another aromatase inhibitor - exemestane, or Aromasin - did in an earlier study and better than tamoxifen, the longest-used breast cancer prevention medicine. Women on anastrozole had more joint pain and hot flashes, but these also were very common in the placebo group - more than half of both groups reported these problems, which often are due to menopause and aging, Cuzick said. Anastrozole users had more cases of a painful wrist condition called carpal tunnel syndrome, and dry eye, but these were relatively rare. Aromatase inhibitors are known to raise the risk of fractures, so many women take bone-strengthening drugs to help prevent that problem. Besides the British cancer research agency, London-based AstraZeneca PLC, which makes the anastrozole used in the study, Arimidex, helped pay for the work, and some researchers are paid speakers for the company. Results were discussed Thursday at the San Antonio Breast Cancer Symposium and published by the British journal Lancet. In a commentary in the journal, Dr. David A. Cameron of Edinburgh Cancer Center in Scotland wrote that healthy women still may resist prevention drugs unless taking them turns out to save lives, not just avoid disease. The cancer conference is sponsored by the American Association for Cancer Research, Baylor College of Medicine and the UT Health Science Center. Lancet study: http://bit.ly/1e0QG8K Cancer meeting: http://www.sabcs.org CDC: http://www.cdc.gov/cancer/breast/index.htm