392P - The prognostic impact of BMI in patients with HR+/HER2- advanced breast cancer on first-line endocrine therapy with or without a CDK 4/6 inhibitor

Background

This study aims to determine the prognostic impact of body mass index (BMI) in patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer (ABC).

Methods

All patients (≥18 years) diagnosed with HR+/HER2- ABC who received first-line endocrine therapy with or without a cyclin-dependent kinase (CDK) 4/6 inhibitor between 2007 and 2020 in the Netherlands were identified from the Southeast Netherlands Advanced Breast Cancer Registry (SONABRE). Patients with a recorded BMI at diagnosis were classified as underweight (BMI: <18.5 kg/m²), normal weight (18.5-24.9 kg/m²), overweight (25-29.9 kg/m²), or obese (≥30 kg/m²). Progression-free survival (PFS) and overall survival (OS) were compared between BMI classes using multivariable Cox regression analyses.

Results

This study included 35 (2.4%) underweight, 580 (39.8%) normal weight, 479 overweight (32.9%), and 362 (24.9%) obese patients. The presence of bone-only metastases increased with a higher BMI, whereas the presence of visceral metastases decreased (p for trend = <0.001). When compared with other BMI classes, underweight patients had a worse WHO performance status (p = <0.001) and were more frequently diagnosed with de novo metastatic disease (p = 0.001). Median follow-up time was 60.9 months (interquartile range (IQR): 37.5-96.0). When compared with normal weight patients, no differences in PFS were observed in underweight (hazard ratio (HR)=1.05; 95% confidence interval (CI): 0.73-1.51), overweight (HR=0.90; 95% CI: 0.79-1.03), or obese patients (HR=0.88 (95% CI: 0.76-1.02). However, the OS of underweight patients (HR=1.45; 95% CI: 0.97-2.15) tended to be worse, whereas the OS of overweight (HR=0.99; 95% CI: 0.85-1.16) and obese patients (HR=1.04; 95% CI: 0.88-1.24) was similar to the OS of normal weight patients.

Conclusions

In this cohort of 1,456 patients with HR+/HER2- ABC, overweight and obesity were prevalent, while underweight was uncommon. When compared with normal weight patients, overweight and obese patients did not experience a decrease in either PFS or OS. Interestingly, however, underweight seemed to be an adverse prognostic factor for OS.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Maastricht UMC+.

Funding

Roche, Pfizer, Novartis, Eli Lilly, Daiichi Sankyo, AstraZeneca, and Gilead.

Disclosure

S. Lammers: Financial Interests, Institutional, Funding: AstraZeneca; Financial Interests, Institutional, Research Grant: Eli Lilly; Financial Interests, Personal, Other, Financial support to attend the ESMO Breast 2023 Congress: ESMO. I.J.H. Vriens: Financial Interests, Institutional, Funding: AstraZeneca; Financial Interests, Institutional, Research Grant: Pfizer, Eli Lilly. M. Meegdes: Financial Interests, Institutional, Funding: Roche, Pfizer, Novartis, Eli Lilly, Gilead. J. Tol: Financial Interests, Institutional, Advisory Role: Amgen. N. Teeuwen: Financial Interests, Institutional, Funding: Roche, Pfizer, Novartis, Eli Lilly, Daiichi Sankyo, AstraZeneca, Gilead. S. Geurts: Financial Interests, Institutional, Funding: Roche, Pfizer, Novartis, Eli Lilly, Daiichi Sankyo, AstraZeneca, Gilead; Financial Interests, Personal, Invited Speaker: AstraZeneca. V. Tjan-Heijnen: Financial Interests, Institutional, Funding: AstraZeneca, Novartis, Eli Lilly, Roche, Pfizer, Daiichi Sankyo, Gilead; Financial Interests, Personal, Other, Honorarium: AstraZeneca, Novartis, Eli Lilly; Financial Interests, Personal, Advisory Role: AstraZeneca, Eli Lilly, Novartis. All other authors have declared no conflicts of interest.