[Oral contraceptive and breast cancer: a case-control study]

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Use of Oral Contraceptives as a Potential Risk Factor for Breast Cancer: A Systematic Review and Meta-Analysis of Case-Control Studies Up to 2010

Despite numerous studies evaluating the risk of breast cancer among oral contraception users, the effect of oral contraceptive on developing breast cancer remains inconclusive. Therefore, we conducted a systematic review of literature with meta-analysis in order to quantitative estimate this association. The bibliographic database MEDLINE and EMBASE, and reference lists of identified articles were searched, with no language restrictions, from the start of publication to August 2010. We performed a reanalysis and overall estimate of 79 case-control studies conducted between 1960-2010, including a total of 72,030 incidents, histologically confirmed cases of breast cancer and 123,650 population/hospital controls. A decrease was observed in cancer risk in OC users before age 25 years (0.91, 0.83-1.00). However, the use of OCs before the first full-term pregnancy had a significant increased risk of breast cancer (OR, 1.14, 1.01-1.28, p = 0.04), as did OC use longer than 5 years (1.09, 1.01-1.18, p = 0.02). Pooled crude odds ratios of breast cancer in ever-users of oral contraceptives was 1.01 [95% confidence interval (CI), 0.95-1.07], compared with never-users. There was no significant increase in risk among premenopausal women (1.06, 0.92-1.22), postmenopausal women (0.99, 0.89-1.10), or nulliparous women (1.02, 0.82-1.26). Oral contraceptives do not appear to increase the risk of breast cancer among users. However, OC use before a first full-term pregnancy or using them longer than 5 years can modify the development of the breast cancer.

Relationship between Breast Cancer and Oral Contraceptive Use among Thai Premenopausal Women: a Case-Control Study

Background:

Breast cancer (BC) is an important issue both in medicine and public health as it is the leading malignancy with high incidence and mortality among women worldwide. The objective of this research was to determine the associations of BC with oral contraceptive (OC) use among Thai premenopausal women (TPW).

Materials and Methods:

A case-control study was conducted among TPW attending the National Cancer Institute, with 257 cases and 257 controls in 2013-2014. Cases and controls were matched by age (± 5 years), residential area and duration of attendance. Data were collected with a questionnaire that comprised 2 sections: part 1 socio-demographic characteristics, and part 2 health risk behavior and reproductive factors. The obtained data were analyzed using descriptive and analytic statistics with a computerized statistical package.

Results:

The study participants were mainly 40-44 years old (60 %) with an average age of 39 years. The major BC type was invasive ductal carcinoma (91.8%). Multiple unconditional logistic regression analysis, controlling for possible confounding factors, revealed that TPW with OC use increased the risk of BC by a factor of over 3 times (ORadj=3.39, 95%CI =1.99-5.75). In addition, the greater the duration of OC, the greater the risk (ORadj 6-10 yrs=3.91, 95%CI = 1.99-7.64, ORadj >10 yrs=4.23, 95%CI = 2.05-8.71).

Conclusions:

From our findings, a surveillance system of cancer risk with OC use should be conducted, accompanied by an exercise promotion campaign among risk groups, providing information and counseling for physical exercise and physical activities, weight control and basic adjustment for a healthy lifestyle to reduce BC.

Risk factors of breast cancer: a systematic review and meta-analysis

The etiology of breast cancer might be explained by 2 mechanisms, namely, differentiation and proliferation of breast epithelial cells mediated by hormonal factors. We performed a systematic review and meta-analysis to update effects of risk factors for both mechanisms. MEDLINE and EMBASE were searched up to January 2011. Studies that assessed association between oral contraceptives (OC), hormonal replacement therapy (HRT), diabetes mellitus (DM), or breastfeeding and breast cancer were eligible. Relative risks with their confidence intervals (CIs) were extracted. A random-effects method was applied for pooling the effect size. The pooled odds ratios of OC, HRT, and DM were 1.10 (95% CI = 1.03-1.18), 1.23 (95% CI = 1.21-1.25), and 1.14 (95% CI = 1.09-1.19), respectively, whereas the pooled odds ratio of ever-breastfeeding was 0.72 (95% CI = 0.58-0.89). Our study suggests that OC, HRT, and DM might increase risks, whereas breastfeeding might lower risks of breast cancer.

Câncer de mama: fatores de risco e detecção precoce

Objetivou-se identificar fatores de risco, segundo o INCA, para câncer de mama, analisar conhecimento e realização do AEM, ECM e mamografia, e verificar relação entre idade e escolaridade com conhecimento e realização desses exames. Dados coletados, durante dez meses, por entrevista com mulheres em quimioterapia contra câncer de mama, analisados por freqüência estatística simples. Observou-se concordância com a minoria dos fatores de risco. Todos os exames eram conhecidos e praticados pela maioria, exceto a mamografia realizada pela metade. As mais velhas praticavam principalmente AEM e mamografia, e as mais jovens ECM. Houve relação diretamente proporcional entre conhecimento desses exames e escolaridade. Os profissionais de saúde precisam orientar a população sobre câncer de mama, para permitir tratamentos mais resolutivos e menos mutiladores.

Prevalence of risk factors for breast neoplasm in the city of Maringá, Paraná state, Brazil

The aim of this study was to identify the prevalence of the risk factors for breast cancer among women between 40 and 69 years old in the city of Maringá, Paraná State, Brazil. An analytical, exploratory and cross-sectional study was carried out through a population research at homes in Maringá. The sample was composed of 439 women between 40 and 69 years old. The data were collected by home interviews, stored using the Statistical Package for the Social Sciences (SPSS) software and presented in tables as absolute and relative frequency. The predominant ethnical group was Caucasian with an average age of 52 years. Among risk factors identified in the present study, an expressive number of overweight women were found. It is important and necessary to put in practice actions that identify the modifiable risk factors for the development of breast tumors in order to reduce morbidity and mortality levels due to this pathology.

Oral contraceptive use as a risk factor for premenopausal breast cancer: a meta-analysis

OBJECTIVE

To perform a meta-analysis of case-control studies that addressed whether prior oral contraceptive (OC) use is associated with premenopausal breast cancer.

METHODS

We searched the MEDLINE and PubMed databases and bibliography reviews to identify case-control studies of OCs and premenopausal breast cancer published in or after 1980. Search terms used included breast neoplasms, oral contraceptives, contraceptive agents, and case-control studies. Studies reported in all languages were included. Thirty-four studies were identified that met inclusion criteria. Two reviewers extracted data from original research articles or additional data provided by study authors. We used the DerSimonian-Laird method to compute pooled odds ratios (ORs) and confidence intervals (CIs) and the Mantel-Haenszel test to assess association between OC use and cancer.

RESULTS

Use of OCs was associated with an increased risk of premenopausal breast cancer in general (OR, 1.19; 95% CI, 1.09-1.29) and across various patterns of OC use. Among studies that provided data on nulliparous and parous women separately, OC use was associated with breast cancer risk in both parous (OR, 1.29; 95% CI, 1.20-1.40) and nulliparous (OR, 1.24; 95% CI, 0.92-1.67) women. Longer duration of use did not substantially alter risk in nulliparous women (OR, 1.29; 95% CI, 0.85-1.96). Among parous women, the association was stronger when OCs were used before first full-term pregnancy (FFTP) (OR, 1.44; 95% CI, 1.28-1.62) than after FFTP (OR, 1.15; 95% CI, 1.06-1.26). The association between OC use and breast cancer risk was greatest for parous women who used OCs 4 or more years before FFTP (OR, 1.52; 95% CI, 1.26-1.82).

CONCLUSION

Use of OCs is associated with an increased risk of premenopausal breast cancer, especially with use before FFTP in parous women.

Risk factors for breast cancer: a systematic review of studies with female samples among the general population in Brazil

A systematic review of studies was conducted to determine the characteristics of epidemiological research on risk factors for breast cancer in female samples from the general population in Brazil. Of the 23 articles identified, only 14 were selected for review. Most of the studies were from Southeast Brazil. Three were cross-sectional, conducted in specific populations, and 11 used case-control designs. The sample sizes varied from 40 to 164,269 women. Twenty-nine risk factors were researched, and among these, 11 were investigated in four or more studies. Nulliparity was the most frequent factor, found in 12 of the studies. Prevalence of the factors varied widely among the samples, and since the samples were heterogeneous and the studies presented several methodological limitations, a summary mean was not calculated.