Review: Bisphosphonates reduced treatment-related bone loss in breast, prostate cancers

Treatment decisions for whether or not to use bisphosphonates should be based on an individual patient’s risk for osteoporosis when starting aromatase inhibitors or androgen deprivation therapy for breast or prostate cancer, according to researchers of a recently published review in the Journal of Clinical Oncology.

Using PubMed and the Cochrane Library databases, Canadian researchers identified trials of cancer treatment-induced bone loss in early breast and prostate cancers, and those that studied bisphosphonates for cancer treatment-induced bone loss prevention. Changes in bone mineral density and fracture rates were analyzed.

According to one claims-based retrospective cohort study of 12,368 patients with breast cancer, those patients treated with aromatase inhibitors had higher rates of bone loss compared with controls (8.7% vs. 7.1%; P=.01). Fracture rates were also higher among treated patients (13.5% vs. 10.3%; P=.001).

However, a study conducted by the Austrian Breast Cancer Study Group reported stable BMD among patients who received zoledronic acid compared with those treated with endocrine ablative therapy alone (P<.0001), according to the researchers.

Treatment with androgen deprivation therapy for prostate cancer was also associated with bone loss and fracture risk. One retrospective study of 390 non-metastatic prostate cancer patients reported a decrease in the percentage of patients with normal BMD from 20% in androgen deprivation therapy-naive patients to 0% after >10 years of therapy.

In another review of 50,613 patients with prostate cancer who survived at least five years post-diagnosis, fracture risk increased among those who received androgen deprivation therapy compared with androgen deprivation therapy-naive patients (19.4% vs. 12.6%; P<.001).

Bisphosphonates have also been shown to reverse treatment-related bone loss in early prostate cancer. According to the researchers, several randomized controlled trials reported increased BMD from 3.3% to 5.6% in the spine and 0.7% to 1.6% in the total hip for those who received bisphosphonates, regardless of androgen deprivation therapy status.

“The use of bisphosphonates, including zoledronic acid and risedronate, seems to attenuate bone loss, although optimal dosing is not established, and the long-term impact remains unclear as a result of insufficient follow-up,” the researchers wrote.

J Clin Oncol. 2008;26:5465-5476.