Efficacy of antiobesity medications among breast cancer survivors taking aromatase inhibitors.

Purpose: Aromatase inhibitors (AI) block estrogen synthesis and are used as long-term adjuvant treatment for breast cancer in postmenopausal women. AI use can be associated with weight gain that can lead to increased cardiometabolic risk. The response to anti-obesity medications (AOM) in patients using AI has yet to be studied. We sought to investigate weight loss outcomes of AOM in patients taking AI for breast cancer treatment.

Methods: This is a matched retrospective cohort study of breast cancer survivors on AI using AOM (AOM/AI group). We compared their weight loss outcomes with a group of female patients with obesity, without a history of breast cancer or AI use, on AOM (AOM group). The primary endpoint was total body weight loss percentage (TBWL %) at the last follow-up. We performed mixed linear regression models, including diabetes status at baseline, to assess associations between use of AOM with/without AI with total body weight loss percentage (TBWL%).

Results: We included 124 patients: 62 in the AOM/AI group (63.6 ± 10 years, body mass index [BMI] 34.3 ± 7.1 kg/m²) and 62 in the AOM group (62.8 ± 9.9 years, BMI 34.6 ± 6.5 kg/m²). The mean time of follow up was 9.3 ± 3.5 months, with no differences among the two groups. The AOM/AI group had a lower TBWL% compared to the AOM group at the last follow-up -5.3 ± 5.0 vs. -8.2 ± 6.3 (p = 0.005). The results remained significant after adjusting for diabetes status (p = 0.0002). At 12 months, the AOM/AI group had a lower TBWL% compared to the AOM group 6.4 ± 0.8% vs. 9.8 ± 0.9% (p = 0.04). The percentage of patients achieving ≥ 5%, ≥ 10%, and ≥ 15% of weight loss at 12 months was greater in the AOM compared to the AOM/AI group. Although the weight loss response was suboptimal, patients in the AOM/AI group had improvement in fasting glucose, glycated hemoglobin, systolic blood pressure, and low-density lipoprotein cholesterol.

Conclusions: The use of AI in breast cancer survivors is associated with less weight loss response to AOM compared to patients without breast cancer history and who do not take AI. Studies are needed to assess the mechanisms behind the differential weight loss response to AOM in women taking AI.