3608 - Prognostic impact of Body Mass Index (BMI) on overall survival in patients with metastatic breast cancer

Background

High BMI has been repeatedly identified as a risk factor for breast cancer (BC), but also as an adverse prognostic factor in women with early-stage BC. Little is known about its impact on outcome in patients with metastatic BC (MBC).

Methods

We used the National ESME-MBC cohort, which includes all consecutive patients (pts) newly diagnosed with MBC between Jan 2008 and Dec 2016 in 18 French comprehensive cancer centres. Women with available BMI at the diagnosis of MBC were selected. Four groups were defined according to WHO classification: underweight (BMI < 18.5 kg/m2), normal weight (18.5-24.9), overweight (25.0-29.9) and obese (≥30.0). Multivariate Cox analyses for OS were conducted in the whole population (primary objective). OS and 1st line progression-free survival (PFS) in subtypes (HER2+, Triple negative BC (TNBC) and HR+ HER2-) were secondary objectives.

Results

Of 22 463 patients in the ESME cohort, 12 999 women had BMI data available. Med BMI was 24.9 kg/m2 (range 12.1-66.5). Pts characteristics are reported in Table. Obesity was associated with more de novo MBC, while underweight pts had more aggressive features. Median follow-up was 48.6 months. Median OS was 47.4 months (95% CI [46.2-48.5]). By multivariate analysis, age, visceral metastases, time to MBC, number of metastatic sites, tumor subtype and BMI were independent predictors for OS. Underweight (but not overweight or obesity) was associated with a worse prognosis (HR 1.29, 95%CI [1.16-1.44]), and this was true in each tumour subtype. Median 1st line PFS was 12.2 months, with similar multivariate results.Table:

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Conclusions

Unlike in early-stage BC, overweight and obesity do not seem associated with poorer OS in MBC women, whatever the subtype, on the opposite of underweight.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

M. Robain: Research grant / Funding (institution), ESME plateform support: Roche; Research grant / Funding (institution), ESME plateform support: AstraZeneca; Research grant / Funding (institution), ESME plateform support: Pfizer; Research grant / Funding (institution), ESME plateform support: BMS; Research grant / Funding (institution), ESME plateform support: DAIICHI Sankyo. All other authors have declared no conflicts of interest.