Low doses of lasofoxifene reduce all common problems in postmenopausal women: Study

Low doses of the medication lasofoxifene can reduce the risk of vertebral and non-vertebral fractures, ER-positive breast cancer, coronary heart disease and stroke in postmenopausal women with osteoporosis. That's the finding of a new study in the latest issue of the New England Journal of Medicine.

Lasofoxifene is a non-steroidal selective estrogen receptor modulator (SERM) that has been shown to decrease bone loss and bone weakening, and reduce cholesterol levels, all common problems in postmenopausal women. However, its impact on other health issues for this population was not well understood.

"This is the first SERM that reduces the risk of all of these conditions at once," says Steven Cummings, M.D., of the San Francisco Coordinating Center at the California Pacific Medical Center Research Institute, and the lead author of the study. "Not only did it reduce vertebral fractures, which was not unexpected, it also reduced the risk of non-vertebral fractures - injuries to the arms, legs, ribs, hips - that are the most common injuries to people with osteoporosis and the main causes of disability."

The researchers followed 8,556 women, ages 59 to 80, over the course of 5 years. Two thirds of the women were given a daily dose of lasofoxifene (either 0.25mg or 0.5mg) and the other third were given a placebo.

The women were given lateral spine radiographs at 12, 24, 36, and 60 months to measure bone density and identify possible fractures. The women also underwent annual mammograms and clinical breast exams to detect breast cancer.

At the end of the five years patients who took lasofoxifene experienced fewer vertebral fractures than the placebo group - a 58 percent reduction in the patients taking 0.5mg a day and 31 percent in the lower dose group - and non-vertebral fractures (24 percent and 10 percent respectively). Those taking lasofoxifene also experienced increases in bone density compared to the placebo group.

Patients taking lasofoxifene experienced a reduction in their risk of estrogen receptor (ER) positive breast cancer (81 percent and 48 percent respectively), and a reduction in LDL (the so-called bad) cholesterol of around 16 percent.

The researchers say the results were not all positive. Patients taking lasofoxifene were at higher risk of experiencing a venous thromboembolic event or blood clot.

"We know that other SERMs, such as raloxifene, also increase a person's risk of blood clots, so this finding was not a surprise to us," says Dr. Cummings. "Even so, we have never found a treatment that has the array of beneficial effects as lasofoxifene with fewer serious side effects. With other treatments, such as Tamoxifen and estrogen, we have seen an increased risk for women of endometrial cancer but in lasofoxifene we did not see that at all."

While the study results are promising the drug is unlikely to be available to women in the U.S. any time soon. The FDA recently rejected pharmaceutical company Pfizer's request for approval, meaning that while it is approved and available in Europe, it is not available here in the U.S.

Dr. Cummings and several of the other researchers involved in this study received consulting grants from Pfizer, the manufacturer of lasofoxifene. However, to reduce questions about conflict of interest or bias an independent scientific advisory committee, consisting of investigators not employed by Pfizer, oversaw the study design and analysis, and wrote the paper and approved it for publication.