Risk factors for breast cancer and their association with molecular subtypes in a population of Northeast Brazil

The risk factors for breast cancer (BC) among women in Brazilian populations are poorly understood. To date, few Brazilian studies have addressed the potential association between risk factors and molecular BC subtypes. This case-control study aimed to identify risk factors for BC in a population of Northeast Brazil.

Data from 313 patients with invasive BC and 321 healthy controls were obtained from medical records from two cancer treatment centres and personal interviews. Of the 313 BC patients, 224 (71.6%) had reached menopause. The following distribution of subtypes was found among 301 patients: (1) Luminal A: 54 (17.9%); (2) Luminal B: 175 (58.1%); (3) HER2/neu: 29 (9.7%); and (4) triple-negative breast cancer (TNBC): 43 (14.3%). Odds ratios (ORs) and confidence intervals (CIs) were determined using regression analysis.

Regression modelling indicated that family history, obesity (≥ 30.0 kg/m²), alcohol consumption and contraceptive use increased the overall risk of BC 1.78 (95% CI: 1.22-2.59), 1.69 (95% CI: 1.08-2.63), 2.21 (95% CI: 1.44-3.39) and 2.99 (95% CI: 2.09-4.28) times, respectively. After stratification for menopausal status, alcohol consumption increased the risk of BC 4.15 (95% CI: 2.13-8.11) times, and obesity, as a single variable, increased the risk of BC 2.02 (95% CI: 1.22-3.37) times, only among postmenopausal women. In a case-control analysis, the risk of TNBC and Luminal B breast cancer were 4.06 (95% CI: 1.58-10.42) and 1.87 times (95% CI: 1.13-3.11) higher, respectively, in obese women than in non-obese women. Furthermore, alcohol consumption increased the risk of Luminal A and B subtypes 7.08 (3.40-14.73) and 1.77 (1.07-2.92) times, respectively.

Family history, contraceptive use, obesity and alcohol consumption increased the risk of BC. Obesity and alcohol consumption differentially increased risk of TNBC and Luminal molecular subtypes.