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Bone Loss Associated With Aromatase Inhibitor Therapy for Breast Cancer Confirmed: Presented at ASCO

By Paula Moyer

ATLANTA, G.A. -- June 4, 2006 -- An analysis involving more than 12,000 breast cancer patients confirms the findings seen in earlier small trials that patients who receive aromatase inhibitors face an increased risk of bone loss and clinical fractures, according to findings presented these here at the American Society of Clinical Oncology 2006 Annual Meeting (ASCO).

"Women receiving aromatase inhibitors for breast cancer should be monitored and treated to alleviate bone loss risk," said principal investigator Betty A. Mincey, MD, director, Multidisciplinary Breast Clinic, Breast Cancer Program, Mayo Clinic, Jacksonville, Florida.

Strategies to prevent bone loss in these women include screening, weight-bearing exercise, supplemental calcium and vitamin D, and bisphosphonate therapy, Dr. Mincey said.

Although smaller studies showed this association between aromatase inhibitor use and bone loss, the link was not confirmed in a large population until now.

They obtained medical and pharmacy claims data from more than 5 million beneficiaries who participated in the managed care plan between January 1, 1998 and January 31, 2005. Among the beneficiaries, the investigators identified 12,368 women who had made at least 2 breast cancer claims in a 6-month period. The group had not had any bone metastasis or any prior osteoporosis or fracture claims. The investigators excluded patients who received antiestrogen therapy.

The investigators subsequently identified 1,354 women who received the aromatase inhibitors anastrozole, exemestane, or letrozole. Their bone loss results and osteoporosis (including osteopenia, as well as clinical fractures) were compared against those of 11,014 controls who did not receive an aromatase inhibitor.

The observation start-date for the aromatase inhibitor and control groups was defined as the service date of the first aromatase inhibitor claim and for the first breast cancer claim, respectively.

Univariate analysis showed that the prevalence of osteoporosis was 8.7% in the aromatase inhibitor group and 7.1% in the control group. Aromatase inhibitor use was associated with a relative risk (RR) ratio of 1.3 (P =.01).

Treated patients also had a significantly elevated risk of bone fracture, with an RR of 1.4; 13.5% of treated patients and 10.3% of controls had clinical fractures (P =.001).

When the investigators adjusted for age and comorbidities, the risk of osteoporosis increased by 27% and the risk of fracture increased by 21% for patients treated with aromatase inhibitors (P =.02).

Noting the limitations associated with retrospective analyses, the investigators called for further research to identify the subgroups of patients who would benefit most from preventive therapy for osteoporosis and to assess the effectiveness of various interventions designed to help reduce bone loss in patients who receive aromatase inhibitors.


[Presentation title: Risk of Cancer Treatment-Associated Bone Loss and Fractures Among Women With Breast Cancer Receiving Aromatase Inhibitors. Abstract 557]

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