Pill linked to increased breast cancer risk

In a nested case-control study of 1102 women aged 20–49 who were diagnosed with invasive breast cancer between 1990 and 2009, researchers found that oral contraceptive use within the previous year increased risk by 50%, compared with a control group who reported past use or never using the pill.

The authors used electronic pharmacy records to gather detailed information on oral contraceptive use, including drug name, dosage and duration of medication.

Recent users filled at least one prescription in the past year for low- (24%), moderate- (78%) and/or high-oestrogen dose (1%) oral contraceptives. 

The risk was more strongly associated with oestrogen receptor positive (ER+) than ER– breast cancer but the result was not statistically significant. Overall risk increased with the increasing number of pills dispensed.

Recent use of oral contraceptives involving high-dose oestrogen, ethynodiol diacetate or triphasic dosing with