Bisphosphonates Useful in Older Women With Breast Cancer

Published: Dec 13, 2013 | Updated: Dec 16, 2013

By Ed Susman , Contributing Writer, MedPage Today

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SAN ANTONIO -- Use of bisphosphonates benefits postmenopausal women with breast cancer the most, a meta-analysis that scrutinized outcomes in 17,000 breast cancer patients suggests.

Among 1,1036 postmenopausal women selected from a meta-analysis, 21.9% experienced distant recurrences of breast cancer if they were not on bisphosphonate therapy compared with 18.4% of women who were taking bisphosphonates -- a 3.5% difference that was highly statistically significant (P=0.0003), according to Robert Coleman, MBBS, MD, professor of medicine at the University of Sheffield in Sheffield, England.

During that same 10-year period, distant bone metastases occurred in 8.8% of postmenopausal women not treated with bisphosphonates compared with 5.9% of those who were on the treatments -- a 2.9% difference that also was highly significant (P<0.0001), Coleman reported at the annual San Antonio Breast Cancer Symposium.

In a related presentation, another team of researchers found no benefit in taking bisphosphonates as post-neoadjuvant therapy in the Neo-Adjuvant Trial Add-On (NATAN).

However, Gunter von Minckwitz, MD, PhD, chairman of the German Breast Group at Neu-Isenburg, told MedPage Today that there was a trend in favor of bisphosphonates among postmenopausal women in his study of women 55 years of age or older that "is in concordance with the meta-analysis."

When he and his colleagues write treatment guidelines, von Minckwitz said that it is likely bisphosphonates will be recommended for use in postmenopausal women with breast cancer.

For the meta-analysis, Coleman and colleagues reviewed data from 15 years of bisphosphonate trials, including seven trials involving the use of clodronate. From those trials, they identified 5,053 patients for the meta-analysis. In 29 trials involving the use of aminobisphosphonates, the research team added 12,738 patients for inclusion in the study. About 65% of the aminobisphosphonates used in the trials was zoledronic acid. Oral ibandronate accounted for another 24%.

In all of the women in the study, breast cancer recurrence was decreased by 1.1% in those on bisphosphonates (P=0.08); and distant recurrences were reduced 1.4% in women on bisphosphonates (P=.03). In the whole cohort, bone recurrences were reduced by 1.5%, which was significant (P=0.0009).

Coleman also found that breast-cancer-specific mortality was reduced by 3.1% from 18.3% among postmenopausal women not on bisphosphonates to 15.2% for those on the therapy, also a significant finding (P=0.004). All-cause mortality was also significantly in favor of postmenopausal women on bisphosphonates (23.8% to 21.5%, P=0.007).

"Adjuvant bisphosphonates reduce bone metastases and improve survival in postmenopausal women," Coleman said. "We did not see any significant effects on non-breast-cancer deaths, contralateral breast cancer, or loco-regional recurrence."

The NATAN trial, von Minckwitz said in a press briefing, assigned 343 women after breast cancer surgery to zoledronate; another 350 were assigned to observation. The researchers cut the trial short when it appeared that recurrence events were less than half of what was expected and the chance of finding a positive result was remote.

The researchers found no difference in disease-free survival and no difference in overall survival. Von Minckwitz demonstrated a slight trend in favor of bisphosphonate therapy for women over 55 years of age. However, none of the subgroups scrutinized achieved statistical significance.

"In this first randomized post-neoadjuvant study, treatment of zoledronate does not improve outcome in patients without a pathological complete response after neoadjuvant anthracycline-taxane based chemotherapy for early breast cancer," von Minckwitz said. He said the researchers did not observe any new safety signals for zoledronate.