Zoledronic acid for treatment of osteopenia and osteoporosis in women with primary breast cancer undergoing adjuvant aromatase inhibitor therapy: a 5-year follow-up

Purpose: This study was designed to explore whether zoledronic acid could prevent expected loss of bone mineral density (BMD) in postmenopausal women with pre-existing osteopenia or osteoporosis who were initiating adjuvant letrozole therapy for primary breast cancer. Methods: Between June 2006 and July 2007, 60 postmenopausal women with estrogen and/or progesterone receptor-positive breast cancer and a BMD T-score ≤−2.0 were enrolled. Participants received letrozole 2.5 mg and vitamin D 400 IU daily, calcium 500 mg twice daily, and zoledronic acid 4 mg every 6 months for a maximum of 5 years or until disease progression. BMD at the lumbar spine and femoral neck was recorded at the start of the study and annually for 5 years. Patients were evaluated for fractures every 6 months for the duration of the trial. Results: After 5 years, mean BMD increased significantly by 11.6 % (p = 0.01) at the lumbar spine and by 8.8 % (p = 0.01) at combined sites. Femoral neck BMD increased by 4.2 %, although this was not significant (p = 0.23). At the end of the trial, BMDs were consistent with osteoporosis in 7 % and osteopenia in 36 % of the patients. A total of six fractures were reported after 417 individual assessments. Conclusions: Zoledronic acid appears to prevent further bone loss in postmenopausal breast cancer patients with osteopenia and osteoporosis starting treatment with letrozole. These findings were maintained at 5 years and support concurrent initiation of bisphosphonate and aromatase inhibitor therapy in this high-risk population.