Oral contraceptives and breast cancer

A study recently published in the journal Cancer Epidemiology, Biomarkers & Prevention alerts us to a serious risk of breast cancer for young women taking even the newer oral contraceptives, especially levonorgestrol. The authors note:

"Previous studies convincingly showed an increase in risk of breast cancer associated with current or recent use of oral contraceptives in the 1960's to 1980's. The relation of contemporary oral contraceptive formulations to breast cancer risk is less clear."

The authors assessed specific formulations of contraceptive use by 116,608 female nurses aged 25 to 42 years for 12 years. What did the data show?

"During 1,246,967 person-years of follow-up, 1,344 cases of invasive breast cancer were diagnosed...Current use of any oral contraceptive was related to a marginally significant higher risk. One specific formulation substantially accounted for the excess risk: the relative risk for current use of triphasic preparations with levonorgestrel as the progestin was 3.05."

That's a 300% increase in the risk of breast cancer. The authors conclude:

"Current use of oral contraceptives carries an excess risk of breast cancer. Levonorgestrel used in triphasic preparations may account for much of this elevation in risk. Impact: Different oral contraceptive formulations may convey different risks of breast cancer; ongoing monitoring of these associations is necessary as oral contraceptive formulations change."