Does obesity increase the risk of breast cancer recurrence?

Clinical studies have shown that obesity is a risk factor for recurrence in postmenopausal women with hormone receptor–positive (HR+) breast cancer. In addition, some evidence suggests that women with obesity do not obtain similar protection from aromatase inhibitors as women with healthy weight. However, data on this issue are limited. To further examine the associations of body mass index (BMI) with breast cancer recurrence, a cohort study was conducted using data from the Danish Breast Cancer Group. The study, which was conducted over an 18-year period, enrolled postmenopausal women diagnosed with stage I to III HR+ breast cancer who were receiving adjuvant endocrine therapy with aromatase inhibitors (e.g., anastrozole, letrozole). Patients were classified into four categories based on BMI: healthy weight (18.5–24.9), overweight (25–29.9), obesity (30–34.9) and severe obesity (≥ 35). Patients with a healthy weight were the reference group in statistical analyses. Patients began follow-up six months after breast cancer surgery and follow-up was continued until the first event of recurrence, contralateral breast cancer, new primary malignant neoplasm, death, emigration, end of clinical follow-up at 10 years, or until the study end date. Cox regression was used to estimate crude and adjusted hazard ratios (HRs) with 95% confidence intervals (CIs), adjusting for patient, tumour and treatment characteristics. Results showed the following: A total of 13,230 patients with information on BMI were enrolled (median age at diagnosis, 64.4 years). A total of 1,587 recurrences were noted, during a median follow-up of 6.2 years. Multivariable analyses revealed increased recurrence hazards associated with obesity (adjusted HR, 1.18 [95% CI, 1.01–1.37]) and severe obesity (adjusted HR, 1.32 [95% CI, 1.08–1.62]) compared to patients with a healthy weight. Patients with overweight also had a greater risk of recurrence, but the results were not statistically significant (adjusted HR, 1.10 [95% CI, 0.97–1.24]). The investigators conclude that, in this study, obesity was associated with an increased risk of breast cancer recurrence among postmenopausal patients with HR+ early-stage breast cancer treated with aromatase inhibitors. The results of this large, population-based cohort study support previous research suggesting that patients with obesity treated with aromatase inhibitors may derive less benefit from their adjuvant endocrine therapy than patients with a healthy weight. The authors encourage further research into whether women with obesity and early-stage HR+ postmenopausal breast cancer should be offered other endocrine therapies such as tamoxifen rather than the currently recommended aromatase inhibitors to improve their prognosis. Reference 1. Harborg S, Cronin-Fenton D, Jensen MBR, et al. Obesity and risk of recurrence in patients with breast cancer treated with aromatase inhibitors. JAMA Network Open 2023;6(10):e2337780. (accessed October 17, 2023).

Does obesity increase the risk of breast cancer recurrence?

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