For the millions of women who are already taking medications to help improve bone density, there may be more than one benefit. New results from a landmark women’s health study raised the exciting possibility that bone-building medications such as Actonel and Fosamax may help lower the risk or even prevent breast cancer.
The women who were already using these medications when the study began were approximately one-third less likely to develop invasive breast cancer over the next seven years when compared to the women who were not taking these pills, doctors reported on Thursday. However, the study alone is not enough to prove that these drugs, called bisphosphonates, prevent breast cancer. More definitive studies should be able to give us a clearer answer in a year or two.
This information greatly amplifies the hopeful buzz that started last year when the researchers reported that bisphosphonates reduced the chances that cancer would relapse in women that have already been treated for the disease.
Dr. Peter Ravdin, from the University of Texas Health Science Center at San Antonio, said, “Now we’re actually looking at this in the general population – healthy women who have never had breast cancer. And it looks like it’s protective in those women as well.” Ravdin help review the research for the San Antonio Breast Cancer Symposium, where the results were reported on Thursday, said, “This is very promising.” Millions of women are already taking bisphosphonates for bone-thinning osteoporosis, or to help prevent fractures from cancer that has spread into their bones.
The medications range from $100 dollars for a three-month supply of the generic versions of Merck & Co. Inc.’s Fosamax pills to as much as $1,200 dollars for an infusion of Novartis AG’s Zometa, which is given every six months to treat osteoporosis. Other brands that have these kinds of medications are Warner Chilcott PLC’s Actonel and GlaxoSmithKline PLC’s Boniva.
After finding out last year that Zometa cut the risk of cancer recurrence, doctors started to wonder if it just making the bones more resistant to the spread of cancer, or does it have wide anti-tumor effects that may help prevent the cancer from developing in the first place?
Dr. Rowan Chlebowski, from Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center in Torrance, California, sought these answers from the Women’s Health Initiative, which is a federally funded study that is best know for revealing previously unrecognized risks from progestin and estrogen pills that are taken after menopause.
Of the 151,592 participants in the study, 2,216 were taking the bisphosphonates, mostly Fosamax, when the study first began. Approximately seven years later, 31 percent fewer invasive breast cancer cases have occurred among those women when compared with the others. The benefit still persisted even after the researchers took into account differences in smoking, weight, age, vitamin D and hormone use, and other things that affect bone density and the risk for breast cancer.
However, the women that were taking bisphosphonates were more likely to develop a noninvasive tumor of the milk duct called DCIS and Chlebowski said that this would be an acceptable trade-off. For every 1,000 women that took the bisphosphonates for one year, one fewer case of invasive, life-threatening breast cancer would occur. Overall, the results from the study suggest that bisphosphonates have direct anti-cancer effects and are not just helping the bones resist the spread of cancer.
Chlebowski, who has consulted the makers of bisphosphonates and other cancer prevention medications, said that if the medications only worked in the bone marrow then it would not be influencing incidence of new cancers.
A second study also supported that view. Dr. Gad Rennert, from the Technion-Israel Institute of Technology in Haifa, Israel, compared approximately 2,000 women that were postmenopausal with breast cancer to 2,000 similar women that did not have the disease. He said those that had the cancer were 29 percent less likely to have been taking the bisphosphonates. However, neither of the studies collected information about the side effects. Bisphosphonates can cause muscle, bone or joint pain and in rare cases, jawbone decay can occur.
Dr. Eric Winer, from the Dana-Farber Cancer Center in Boston, said, “These are drugs that, generally speaking, are relatively well tolerated,” and are fairly safe, but they still should not be taken for prevention of cancer until more definitive studies show their benefits and risks.
The only medications approved now for the prevention of breast cancer in healthy women at higher risk are the hormone blockers raloxifene and tamoxifen. The side effects for these medications are high blood pressure, hot flashes and a higher risk of blood clots, which have limited their use.
