Background:
Obesity, typically measured by body mass index (BMI), is an established risk factor for poor pathological outcomes in breast cancer. However, its mechanistic influence on tumour biology and patient prognosis remains underexplored, particularly in North African populations. This retrospective study aimed to investigate the relationship between BMI, clinicopathological features, and survival outcomes among Tunisian breast cancer patients.
Methods:
A single-centre retrospective study was conducted at the Salah Azaïz Institute (Tunis) from 2014 to 2021, comprising 490 breast cancer patients categorized into three groups by BMI: normal weight (G1: <25 kg/m²), overweight (G2: 25–29.9 kg/m²), and obese (G3: ≥30 kg/m²). Clinical and pathological variables were compared across BMI groups. Progression-free survival (PFS) and disease-free survival (DFS) were assessed using Kaplan–Meier and Cox regression models.
Results:
The patient cohort across the three BMI categories included 30.6% G1, 29.6% G2, and 40.0% G3 patients. Obesity among patients was associated with adverse tumor features, including larger tumor size, lymph node involvement, higher Scarff–Bloom–Richardson (SBR) grade, and elevated Ki-67 and mitotic indices (all p < 0.001). The triple-negative subtype was more prevalent among G3 (p = 0.045). Both five-year DFS and PFS were significantly shorter in obese patients. Notably, tumor-infiltrating lymphocytes (TILs) ≥50% were associated with improved DFS and PFS, especially in the obese subgroup. In those patients receiving adjuvant chemotherapy, DFS decreased from 121 months (normal BMI) to 71 months (obese; p = 0.005).
Conclusions:
Obesity was strongly associated with more aggressive tumor phenotypes and poor survival outcomes. Therapeutic efficacy of standard treatment modalities appeared reduced in obese patients, while high TILs conferred survival benefit. These findings highlight the need for designing BMI-tailored treatment strategies for breast cancer patients.