ORLANDO – Cumulative evidence over the years has shown that bisphosphonates reduce distant metastases in postmenopausal women with early-stage breast cancer but that effect does not seem to extend to younger, premenopausal women who may experience adverse effects with bisphosphonates, nor has it been replicated in other types of cancer, such as lung or prostate, Robert Coleman MBBS, MD, said in a presentation marking the 50th anniversary of the publication of the first papers describing the then-new class of drugs.
“We have some science – at least in postmenopausal breast cancer – [showing] that we’re really making a difference, but we don’t understand why it’s not working in the other patients or in the other diseases,” said Dr. Coleman of the University of Sheffield (England) at the annual meeting of the American Society for Bone and Mineral Research.
Mixed findings in early studies
Early studies showing the metastases-prevention effects of bisphosphonates were with clodronate. In one study, Dr. Coleman said, researchers found that oral clodronate at a dose of 1,600 mg/day as a supplementary treatment to standard treatment for primary, operable breast cancer reduced the risk of bone metastases in a cohort of 1,069 patients with stage 1-3 breast cancer (hazard ratio, 0.692; P = .043) over 5 years (Breast Cancer Res. 2006 Mar 15. doi: 10.1186/bcr1384). Another trial, of 302 patients with breast cancer who received oral clodronate at 1,600 mg/day for 2 years, found that 20.4% of patients who received oral clodronate had died by 8.5 years of follow-up, compared with 40.7% of those who did not receive the intervention (Ann Oncol. 2008;19[12]:2007-11).
However, those results were in conflict with findings from an earlier study in which researchers followed patients with breast cancer who received 1,600 mg/day of oral clodronate or placebo for 3 years. They found a similar number of bone metastases in the clodronate and placebo groups (32% and 29%, respectively), as well as a lower overall disease-free survival rate at 10 years for the clodronate group, compared with the placebo group (45% vs. 58%; Acta Oncol. 2004;43[7]:650-6).“For various other reasons, clodronate did not gain traction as a therapeutic strategy in early-stage breast cancer,” said Dr. Coleman, although emerging evidence showed that other bisphosphonate agents were effective in some patients with breast cancer.
In a 2009 article, Gnant et al. reported that premenopausal patients, who underwent primary surgery for stage 1 or stage 2 breast cancer and received standard goserelin therapy for induced menopause and endocrine therapy (either tamoxifen or anastrozole) in addition to treatment with zoledronic acid, had a disease-free survival rate of 94.0% at a median 47.8 months of follow-up (N Eng J Med. 2009;360:679-91). After a median 94.4 months of follow-up, the investigators reported a lower risk of disease progression (HR, 0.77; 95% confidence interval, 0.60-0.99; P = .042) and death (HR, 0.66; 95% CI, 0.43-1.02; P = .064; Ann Oncol. 2015;26[2]:313-20).
In his own group, Dr. Coleman and colleagues recruited patients with early-stage breast cancer in the AZURE trial, a phase 3 study of 3,360 patients who received standard therapy with or without zoledronic acid 4 mg every 3-4 weeks for 6 doses, followed by 8 doses every 3 months then 5 doses every 6 months (N Eng J Med. 2011;365:1396-405). “We saw no effect,” said Dr. Coleman. “[That was] very different from what was shown by [Dr.] Gnant.”
For a subgroup of postmenopausal patients, Dr. Coleman and colleagues found that the adjusted HR for disease-free survival was 0.82 for women who were more than 5 years postmenopausal (95% CI, 0.67-1.00) at the time of breast cancer and bisphosphonate treatment, but women younger than 40 years had worse survival outcomes at 10 years (HR, 1.56; 95% CI, 1.09-2.22) and had a significantly higher risk of death from breast cancer (HR, 1.67; 95% CI, 1.16-2.40; J Bone Oncol. 2018 Sep 27. doi: 10.1016/j.jbo.2018.09.008).