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/m 2 ), 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.
- • Family history, contraceptive use, obesity and alcohol consumption increase overall risk of breast cancer.
- • Obesity and alcohol consumption increase risk of breast cancer among post-menopause women.
- • Obesity is associated with increased risk of triple negative breast cancer.
- • Alcohol consumption increases risk of Luminal A and Luminal B molecular subtypes.
- • Nulliparity decreases the risk of post-menopause women and increases the risk of pre- menopause women.
According to the World Health Organization (WHO) in 2018 an estimated number of 2,088,849 new BC cases contributed to 11.6% of all cancer deaths worldwide . An increase of BC was mostly observed in developing countries due to changing lifestyles and longer life expectancies, whereas in most developed countries, the incidence remained stable or even declined . With more than 209 million inhabitants, Brazil is the largest country in Latin America and BC is currently contributing to 29.5% of all neoplasms among women . For the time from 2020 to 2022 the National Institute of Cancer predicted 66,280 new cases for each of the years . In the two largest urban centres of Brazil, namely, São Paulo and Rio de Janeiro, and in other regions in southern, southeastern and midwestern Brazil, the incidence of BC has stabilised over the last 10 years . This is in contrast to the northeastern region, where the incidence of BC increased between 2005 and 2021 from 27.23 to 44.29 new cases per 100,000 women .
In the literature, it is well established that reproductive, anthropometric and lifestyle-related factors modify the risk of BC . It was estimated that approximately one-third of all post-menopausal BC cases in the United States are caused by modifiable and therefore preventable lifestyle-related risk factors . In the United Kingdom, 6.9% of all BC cases were attributed to obesity and overweight as a single risk factor for the disease . Obesity was associated with increased risk of BC among post-menopause women, whereas an inverted association was identified for pre-menopause women . Additionally, risk factors can be differentially associated with molecular BC subtypes. Obesity and overweight of premenopausal women, respectively, several reproductive risk factors, were associated with the triple negative molecular BC (TNBC) subtype, that is defined by the absence of expression of hormone receptors and HER2/NEU . Compared to other molecular subtypes the therapeutic opportunities for treatment of TNBC are reduced and the high graded, aggressive tumours have a poor prognosis .
Previous Brazilian case-control BC studies addressed on anthropometric measures, life-style related risk factors and family history . With the exception of a database study by Menezes et al. all of these studies referred to data from populations in the southern, south-eastern and central eastern regions of Brazil. Only few studies addressing the identification of risk factors, were performed in north-eastern Brazil, a region where BC incidence is increasing . Furthermore, possible associations between TNBC, respectively other molecular subtypes and risk factors, so far were only addressed in one single Brazilian case-case study . The frequency of TNBC in the Brazilian Northeast region varied from 16.1% to 17.4% and was more common among premenopausal patients, respectively patients aged ≤ 40 years if compared to other molecular subtypes .
Since 2003, Brazil has had a public programme for the early detection of breast cancer, and mammography screening has been promoted in the month of October (“Outubro rosa”). In northeastern Brazil, most women rely on information about BC from television, and very little information is provided about preventable risk factors that can be modified to decrease the risk of BC. There is an urgent need to identify risk factors for BC and TNBC in this population and, if these factors are modifiable, to promote their prevention in health campaigns. The present study focused on the identification of BC risk factors in a population from northeastern Brazil and the association of risk factors with TNBC and other molecular subtypes.