“In patients with bone-only metastasis, we could not demonstrate antitumor effects of zoledronic acid,” conclude Dr. Naoto T. Ueno, at the University of Texas MD Anderson Cancer Center in Houston, and colleagues.
They explain in their paper that preclinical studies have indicated that bisphosphonates have direct and indirect antitumor effects, but whether it might confer a survival advantage in cancer patients is controversial.
The authors hypothesized that breast cancer patients with bone-only metastases, who general have a long survival, would survive even longer with the addition of zoledronic acid or pamidronate to standard therapeutic agents.
To test this, they identified 314 such patients seen at MD Anderson over a 10-year period. At initial diagnosis of bone disease, 172 patients received zoledronic acid, 77 were treated with pamidronate, and 65 did not receive a bisphosphonate.
On univariate analysis, progression-free survival was better in the no-bisphosphonate group than the in pamidronate group (hazard ratio 0.57; p=0.002) and in the zoledronic acid group (HR 0.72) but this was not significant (p=0.058).
After adjustment for factors such as menopausal status and number of bone metastases, on multivariate analysis there was no significant difference in progression-free survival between the no-bisphosphonate group and the zoledronic acid group (HR 0.80; p=0.235), the report shows.
The same held true for overall survival, with a hazard ratio of 1.34 (p=0.192) in multivariate analysis, Dr. Ueno and colleagues found.
“A present, the use of zoledronic acid for patients with bone metastases is the gold standard because it significantly reduces or prevents skeletal-related events,” they point out.
However, it does not appear to prolong survival and any antitumor effect “remains controversial,” they conclude. “Patients and physicians should have a clear understanding of the potential benefits of bisphosphonate treatment.”