A new pilot study has reported that Boniva (ibandronate) can eliminate dormant breast cancer cells in bone marrow. The study was designed to investigate the medium-term presence of tumor cells in the bone marrow of breast cancer patients and to study the effect of Boniva on such cells. Breast cancer can recur even 10 to 20 years after the original diagnosis. Such late relapse is thought to be caused by dormant breast cancer cells that have found their way to the bone marrow. These tumor cells evade eradication by chemotherapy because they are not dividing at the time of treatment. Bisphosphonates such as Boniva, Fosamax, Actonel and Zometa are drugs used to treat osteoporosis and metastatic bone disease. Bisphosphonates are currently being proposed as possibly being capable of eliminating such cells. The study included 54 women diagnosed with breast cancer two to 10 years previously, but currently in remission.

Bone marrow aspiration is a procedure that extracts a bone marrow specimen (typically from the pelvic bone) using a needle. Bilateral bone marrow aspirates (taken from both the left and the right side) of the study participants were analyzed for tumor cells. Women found to have dormant tumor cells were treated with oral Boniva (50 mg per day) for six months, after which new bilateral bone marrow aspirates were obtained and analyzed for tumor cells.

Dormant tumor cells were found in 18 (33%) of the women, with a median of three disseminated tumor cells found (range: 1-6 cells). All of these patients were treated with Boniva for six months, after which 17 of them were re-evaluated for tumor cells. Tumor cells were found in the bone marrow of only three (18%) of the 17 patients; one tumor cell was detected in two women and three tumors cells were found in the remaining women. Boniva treatment was continued for an additional six months for these three women and no tumor cells were found in any of them after re-examination of the bone marrow. The authors conclude that their pilot study shows a potential treatment effect of Boniva on dormant disseminated tumor cells. Further studies are needed to demonstrate these findings in a larger patient group.