Bone-building Drugs Might Help Fight Breast Cancer
The most recent of several studies involving women who had breast cancer and who also take drugs to strengthen bone shows encouraging results. The study of 1,800 women, published recently in the New England Journal of Medicine, involved those who took hormonal therapy to block estrogen production that fuels growth in certain breast cancers. Half of the group was also given zoledronic acid, or Zometa, intravenously twice a year for three years. Women given Zometa showed a 36 percent reduction in cancer recurrences and metastases, compared to half the group who didn’t get it.
 Four years later, 54 women receiving zoledronic acid and 83 who didn’t get the bone drug had a recurrence, a new cancer in the second breast, or a spreading of cancer to the bone. The question is, shouldn’t all women on hormonal therapy for breast cancer receive Zometa or a similar bone drug? Before prescribing these drugs as standard therapy, researchers plan to examine results from two other large studies now nearing completion. Women taking hormonal therapy are blocking estrogen production, which in turn can cause thinning of bones. Why not add the bone-building drugs to their anti-cancer therapies?
 Cancer cells are known to interact with a type of bone cell called osteoclasts, whose role is to break down bone. Breast cancer cells sometimes migrate to the bones and stimulate osteoclasts, which in turn stimulate cancer cells. It’s a vicious cycle. But what if the cycle can be interrupted?
 Drugs used to treat the bone-thinning disease osteoporosis have been shown to stop osteoclasts from releasing substances that cause bone loss. As osteoclasts stop working, they die. Other studies of bisphosphonates to prevent osteoporosis have shown in lab studies that they might have other anticancer effects. Bisphosphonates affected the ability of cancer cells to stick to surrounding tissue, to invade and grow in numbers. One of the new study’s lead researchers believes that bisphosphonates could squelch the cells that migrate to the bones and hide in marrow, thus affecting the ability of breast cancer to recur.
 Researchers are also investigating whether bisphosphonates could treat cancer that has already metastasized to bone. After determining that they could, zoledronic acid and other bisphosphonates were approved for women with bone metastasis. These therapies were shown in one study to prevent further spread of cancer in bones. Zometa is approved only for bone complications of cancer and is not an official drug for osteoporosis. There is a rare but quite serious side effect, osteonecrosis of the jaw, which has been seen with bisphosphonate use. No instances have been seen in study participants, however.
 Studies are still in progress to investigate whether these bone drugs used in high doses to treat cancer can prevent breast cancer from initially spreading. Results have been mixed. In research now ongoing, there is hope that zoledronic acid could add a benefit to existing breast cancer therapy to the same degree as the magnitude from chemo or hormonal therapy alone. Scientists and physicians are waiting for data from other studies. Clinical trials may have the answers in the near future.
 Source: Gina Kolata; New York Times; Feb. 11, 2009
http://www.nytimes.com/2009/02/12/health/research/12bone.html?th&emc=th
blog article by Anna Dabney
1 comment February 16th, 2009
