Increased physical activity, even when begun later in life, may be associated with a reduced risk of breast cancer among postmenopausal women, according to a new study.
Previous studies have found that regular exercise is associated with a reduced risk of breast cancer, but the amount and intensity have not been determined. It is also unknown whether physical activity after menopause reduces the risk of breast cancer or if lifelong physical activity is needed.
To address these questions, Anne McTiernan, M.D., Ph.D., of the Fred Hutchinson Cancer Research Center in Seattle, and her colleagues surveyed 74,171 postmenopausal women ages 50 to 79 who were enrolled in the Womens Health Initiative Observational Study.
Over 4.7 years of follow-up, there were 1,780 cases of breast cancer diagnosed. Compared with less active women, women who had engaged in strenuous physical activity at least three times per week at age 35 had a 14% lower risk of breast cancer (0.46 cases of breast cancer per 100 women versus 0.56 cases of breast cancer per 100 women). Similar reductions in risk were associated with strenuous activity at ages 18 and 50. Increasing level of total current physical activity was also associated with a reduced risk of breast cancer, but only among women with low to normal weight.
The authors suggest that exercise may lower breast cancer risk by lowering body fat, which in turn lowers the levels of circulating cancer-promoting hormones. The study appears in the September 10 issue of the Journal of the American Medical Association.
Bisphosphonates May Reduce the Risk of Bone Complications
Bisphosphonates appear to reduce the risk of skeletal complications in patients whose cancer has spread to the bone, according to a systematic review of data from past studies. Bisphosphonates are a class of drugs used to treat osteoporosis.
Joy Ross, of the Royal Marsden Hospital in London, and her colleagues examined 30 randomized, controlled trials of patients with bone metastases who were treated with a bisphosphonate or a placebo. Cancers that often spread to the bone include breast cancer, prostate cancer, and multiple myeloma.
In studies that lasted at least 6 months, patients who were treated with a bisphosphonate had a lower risk of fractures, need for radiotherapy, and hypercalcemia. Studies that lasted more than a year showed a statistically significant reduction in the need for orthopedic surgery. There was no reduction in the incidence of spinal cord compression. There was also no difference in survival between the treatment and control groups.
"Our findings show that bisphosphonates need to be given at least 6 months before an effect is seen on skeletal morbidity outcomes," the researchers wrote.
The study appeared in the August 30 issue of the British Medical Journal.
See also News, Vol. 95, No. 17, p. 1273, "Clinical Trials Test Bisphosphonates in Hormone-Sensitive Prostate Cancer."
Linda Wang
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