Endocrine Abstracts

Introduction: Aromatase inhibitors, such as Letrozole or Exemestane, are often used as adjuvant treatment for post-menopausal breast cancer. However, they are known to reduce bone mineral density (BMD). Furthermore, breast cancer patients often undergo chemotherapy with drugs associated to BMD loss by themselves. Therefore, patients treated for breast cancer are subject to a considerable risk of BMD loss, and to alleviate this the treatments are normally combined with an anti-resorptive agent such as zoledronic acid or denosumab. These drugs have proven effective at stopping BMD loss during breast cancer treatment in several trials. A current oncological protocol is to use adjuvant i.v. zoledronic acid 4 mg every 6 months for 4 years while patients undergo treatment with aromatase inhibitors. We have investigated a group of women with breast cancer undergoing this protocol regime in a regular, clinical setting with the aim of determining whether all-cause BMD loss can be halted and/or reversed in an average, unselected population of women with early post-menopausal breast cancer.

Methods: A prospective study of BMD changes in post-menopausal women with breast cancer undergoing adjuvant treatment with aromatase inhibitors and anti-resorptive treatment in a clinical setting. We are currently following this cohort of women from diagnosis to finalized aromatase inhibitor treatment, and data presented here represent an interim analysis after two years of aromatase inhibitor treatment.

Results: A total of 79 women with a mean age of 59.4 years (±6.0) was included. BMD was measured by DXA-scan at baseline, after 12 months and after 24 months. In this interim analysis we found that adjuvant antiresorptive treatment significantly increases BMD after 12 months in all sites; in lumbar spine from 0.920 to 0.975 g/cm² (P<0.001), in total hip from 0.828 to 0.851 g/cm² (P=0.006) and in femoral neck from 0.704 to 0.725 g/cm² (P=0.005). All three sites remained significantly increased compared to baseline after 24 months (P<0.001 at lumbar spine; P=0.017 at total hip; P=0.045 at femoral neck).

Conclusion: Adjuvant treatment with anti-resorptive drugs can, in a short time, significantly improve BMD in women treated for early breast cancer with chemotherapy and aromatase inhibitors, in normal clinical practice.