Obesity Increases Risk of Breast Cancer Recurrence in Postmenopausal Women with Hormone Receptor-Positive Tumours

A recent cohort study conducted by the Danish Breast Cancer Group has revealed that obesity is a significant risk factor for breast cancer recurrence in postmenopausal women with hormone receptor-positive (HR+) breast cancer. The findings demonstrated that both obesity and severe obesity were associated with increased recurrence hazards, emphasising the importance of addressing weight management as part of breast cancer treatment.

This study was published in JAMA Network Open by Harborg S. and colleagues. Clinical evidence has long suggested a link between obesity and an increased risk of breast cancer recurrence in postmenopausal women with hormone receptor-positive (HR+) tumours. This study aimed to further examine the associations between body mass index (BMI) and breast cancer recurrence in this specific patient population, as well as the impact of different BMI categories on recurrence rates.

The cohort study utilised data from the Danish Breast Cancer Group, focusing on postmenopausal women diagnosed with stage I to III HR+ breast cancer between 1998 and 2016. BMI was categorized according to World Health Organization guidelines, including healthy weight, overweight, obesity, and severe obesity. The study began follow-up six months after breast cancer surgery and continued until the first occurrence of recurrence, contralateral breast cancer, new primary malignant neoplasm, death, emigration, end of clinical follow-up at 10 years, or September 25, 2018. Statistical analysis employed Cox regression and adjusted for various patient, tumour, and treatment characteristics.

• A total of 13,230 patients participated in the study, with a median age at diagnosis of 64.4 years.
  
• Over the course of the study, there were 1,587 breast cancer recurrences.
• Patients with obesity had an increased risk of breast cancer recurrence (adjusted hazard ratio: 1.18) compared to patients with a healthy weight.
• Patients with severe obesity had an even greater risk of recurrence (adjusted hazard ratio: 1.32) compared to the healthy weight group.
• Patients with overweight also exhibited an elevated risk, but this did not reach statistical significance (adjusted hazard ratio: 1.10).

The study's findings provide strong evidence that obesity significantly increases the risk of breast cancer recurrence among postmenopausal patients with HR+ early-stage breast cancer, particularly those treated with aromatase inhibitors. These results emphasize the critical role of addressing obesity as part of breast cancer treatment and the need for physicians to be aware of its impact on breast cancer outcomes. Proper weight management can help secure optimal treatment benefits for all patients, reducing the risk of recurrence.

Reference:

Harborg, S., Cronin-Fenton, D., Jensen, M.-B. R., Ahern, T. P., Ewertz, M., & Borgquist, S. Obesity and risk of recurrence in patients with breast cancer treated with aromatase inhibitors. JAMA Network Open,2023;6(10):e2337780–e2337780. https://doi.org/10.1001/jamanetworkopen.2023.37780