A new study presented at the American Society of Clinical Oncology annual meeting in Chicago has reported that use of bisphosphonates may reduce survival among postmenopausal women with nonmetastatic breast cancer. Bisphosphonates are commonly used to treat osteoporosis and bone loss resulting from adjuvant hormonal treatments. They are also used to treat breast cancer that has moved into the bone and have been shown to increase survival times in metastatic breast cancer. It was expected that bisphosphonate use would also have a survival benefit in women with nonmetastatic breast cancer.

The authors compared overall survival of women with stage I, II, or III invasive breast cancer who received any of the new generation nitrogen-containing bisphosphonates (alendronate, ibandronate, pamidronate, risedronate, zoledronate) for osteopenia or osteoporosis with the survival of those who did not. Most bisphosphonates prescribed today are nitrogen-containing since this newer class of drugs has been shown to be more effective than non-nitrogen-containing bisphosphonates (etidronate, clodronate). The study included 696 Detroit women over 50 diagnosed with stage I, II, or III invasive breast cancer during the period 2000 to 2003. Ninety-seven (14%) of the women used nitrogen-containing bisphosphonates.

The difference in overall survival between bisphosphonate users and non-users was not found to be statistically significant at three years (94% percent overall survival among of bisphosphonate users and 88% percent among non-users). However, after adjusting for differences between bisphosphonate users and non-users in age, stage of disease, hormone receptor status, hormonal therapy, and vitamin D and calcium use, a marginally significant difference in survival was found. Unexpectedly, bisphosphonate users had poorer overall survival than non-users. This suggests that bisphosphonates may facilitate cancer cell migration, invasion or tumor establishment. The authors conclude that use of bisphosphonates is not associated with improved overall survival in patients with nonmetastatic breast cancer, even after adjusting for known prognostic factors. In fact, marginally worse overall survival was found. Results of further ongoing research is awaited to clarify the role of bisphosphonates in breast cancer treatment.