A new study has found that specific oral contraceptives are tied to an increased risk of developing breast cancer.
The study results were published in the August 1 issue of the journal, Cancer Research. The research was conducted by Seattle, Washington-based Group Health Research Institute, Group Health Cooperative; the Fred Hutchinson Cancer Research Center; and the University of Washington, wrote the Los Angeles Women’s Health Examiner.
The study authors found that prior research conducted on the relationship between oral contraceptives and breast cancer revealed a slight, increased risk; however, the majority of the studies counted on self-reported use and did not review current birth control pill formulations. The new study involved female enrollees in a large United States integrated healthcare delivery system, according to the Los Angeles Women’s Health Examiner, and involved 1,102 women who were between 20 and 49 years of age and diagnosed with invasive breast cancer from 1990 through 2009. The control patients were comprised of 921,952 women who were randomly selected from enrollment records and matched to breast cancer cases by age, year, enrollment length, and medical chart availability. The specific use of oral contraceptives was taken from electronic pharmacy records and was also subjected to statistical analysis.
The researchers discovered that, in women who had experienced recent oral contraceptive use, with “recent” defined as being within the previous year, there was an associated increased risk for breast cancer defined as 1.5-fold, which was compared to never or former use of oral contraceptives. The risk was greater—1.7-fold—for estrogen receptor–positive, and slightly lower for estrogen receptor negative formulations, which was measured at a 1.2-fold increased risk, the Los Angeles Women’s Health Examiner reported.
The researchers also discovered that recent use of high-dose estrogen birth control risk was 2.7-fold; with ethynodiol diacetate, the increased risk was 2.6-fold; with triphasic dosing with an average of 0.75 mg of norethindrone, the increased risk was 3.1-fold.
The team concluded that recent use of contemporary oral contraceptives is tied to increased risks for breast cancer, which may vary by the medication’s formulation. The team also noted that women who have a family history of breast cancer and/or who carry the BRCA1 or BRCA2 gene are at increased risk for developing breast cancer and this risk exists regardless of if these women do or do not take an oral contraceptive. Taking an oral contraceptive may increase the risk, they added, according to the Los Angeles Women’s Health Examiner.
The authors found that taking oral contraceptives was associated with a 50 percent increased risk for breast cancer for women similar to those who were studied in the research and who were between 20 and 49 years of age.