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Bisphosphonate use decreased contralateral breast cancer risk among ER-positive cases
Monsees GM. J Natl Cancer Inst. 2011;epub ahead of print.
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Overall use of bisphosphonates and extended use of bisphosphonates both were associated with a decreased risk for contralateral breast cancer among women with first primary ER-positive invasive breast cancer.
Researchers used data from the SEER population-based cancer registry for Western Washington State to identify women aged 40 to 79 years for enrollment in the study. They compared 351 women who had contralateral breast cancer with 662 control women with breast cancer but no contralateral breast cancer.
Between both groups, 121 women had ever used bisphosphonates; 88% used alendronate.
Analyses indicated women who had used bisphosphonates for 6 months or longer had a 47% (95% CI, 0.30-0.93) lower risk for contralateral breast cancer compared with women who had never used them. Women who were still using bisphosphonates had an even greater risk reduction, 59% (95% CI, 0.20-0.84), compared with never users.
The researchers also found a link between the duration of use of bisphosphonates and the risk for contralateral breast cancer among women who had ever used or were current users of bisphosphonates, compared with women who had never used them.
“If these findings are confirmed by subsequent studies, the observed reduction in risk of contralateral breast cancer associate with prolonged bisphosphonate use may imply that these agents have anti-tumor effects outside of the adjuvant setting,” the researchers wrote.
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The controversy over the anti-neoplastic properties of bisphosphonates continues. There appears to be clear and convincing evidence that the bisphosphonate zoledronic acid, given at least twice per year for 3 to 5 years adjuvantly for breast cancer, improves disease-free survival in women with suppressed estrogen. At this year’s San Antonio Breast Cancer Symposium, there will be data presented on potential overall survival benefit (or lack thereof) of zoledronic acid in the adjuvant setting in two large randomized clinical trials in women with suppressed estrogen. There also is mounting evidence of a correlation of bisphosphonate use and primary prevention of breast cancer and potentially other cancers. This study is one of several to show such correlation. Correlation does not necessarily imply causation, and potential confounders exist in epidemiologic investigations such as this study. Why is there a lack of acceptance of bisphosphonates as potential antineoplastic agents? One potential reason is that we are not quite sure of the mechanism of their action in this setting. Indeed, there is emerging evidence that the primary effects of bisphosphonates in primary and secondary cancer prevention may lie in their disturbance of the peritumoral stromal microenvironment. As more clinical evidence mounts for potential antitumor effects of bisphosphonates, there will be even more drive to determine the mechanism of such effects.
– Adam M. Brufsky, MD
HemOnc Today Editorial Board member
Disclosure: Dr. Brufsky is a consultant for Novartis.
Earn CME this spring at the HemOnc Today Breast Cancer Review & Perspective meeting to be held March 23-24, 2012 at the Hilton San Diego Bayfront. See details at HemOncTodayBreastCancer.com.