Abstract
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.
Highlights
Breast cancer (BrCa) is the most frequently diagnosed cancer and the leading cause of cancer death in women worldwide
Oral contraceptives (OCs) use longer than 5 years leads to a slight, but significant increase of breast cancer risk (Figure 10)
In our meta-analysis, based on accepted criteria, we found no increased risk of breast cancer associated with use of low-potency/low estrogen-dose oral contraceptives, a finding which was comparable with earlier high-potency/high-dose preparations
Summary
Breast cancer (BrCa) is the most frequently diagnosed cancer and the leading cause of cancer death in women worldwide. It accounts for 23% (1.38 million) of the total new cancer cases and 14% (458,400) of the total deaths in 2008. In Western countries, the incidence has increased BrCa over the last 50 years, and these increases were dramatic in both the 1980s and the 1990s [3,4]. The sharp incidence increases observed after 1985 in the United States and most European countries were mainly due to the combined effects of changes in reproductive factors, prevalence of overweight and obesity, improvements screening mammography, and use of hormone replacement therapy (HRT) [5].
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