Real-World Evidence of the Effect of Body Mass Index on Treatment Outcomes in MBC

Although obesity or overweight is associated with poor prognosis in breast cancer, the prognostic value of body mass index (BMI) in patients with metastatic disease is unclear. The objective of this retrospective study is to assess the potential prognostic significance of BMI with long-term follow-up in patients with metastatic/recurrent breast cancer.

This study included patients who were diagnosed with metastatic/recurrent breast cancer between January 2000 and December 2022. BMI was calculated based on weight at diagnosis of metastatic disease, and patients were classified into 4 groups (underweight, normal, overweight, and obese).

The study population included a total of 679 patients. Median age was 51 years; the majority of patients were premenopausal (62.6%). By breast cancer subtype, 335 (50.7%) patients had hormone receptor–positive disease, 191 (28.9%) had HER2+ disease, and 135 (20.4%) had triple-negative breast cancer (TNBC) disease. By BMI score, 33 (5.5%) patients were classified as underweight, 251 (41.6%) as normal, 124 (20.5%) as overweight, and 196 (32.4%) as obese.

The median overall survival (OS) was 54.9 months in the hormone receptor–positive cohort, and 62.8 months and 20.8 months in the HER2+ and TNBC cohorts, respectively. Lower BMI was associated with poor OS (median OS, <18.5: 15.97 months; ≥25.0: 58.93 months). Decrease more than 5% (median OS: 41.47 months) was also significantly associated with poor OS. Multivariate analysis identified several prognostic factors, including age (hazard ratio [HR], 0.59; P=.008), poor European Cooperative Oncology Group performance status (HR, 8.35; P<.001), TNBC subtype (HR, 2.14; P<.001), visceral metastasis (HR, 2.13; P<.001), ≥5% weight loss during treatment (HR, 1.46; P=.012), and obese BMI group (HR, 0.69; P=.019).

These long-term follow-up results of a retrospective analysis suggest that higher BMI was associated with better survival outcomes compared with lower BMI in patients with HER2+ metastatic breast cancer (MBC).

Source:

Lee KE, Ham A, Lee S, et al. Effects of body mass index on the treatment outcome of patients with metastatic breast cancer in the real world. Presented at the 46th San Antonio Breast Cancer Symposium Annual Meeting, December 5-9, 2023; San Antonio, TX: Abstract PO4-05-11.