Correlation of age at oral contraceptive pill start with age at breast cancer diagnosis.

Breast cancer is progressively diagnosed with increasing age. This study aimed to determine whether women who started using the oral contraceptive pill (OCP) at an early age developed breast cancer earlier than women who started using the OCP later in life. A database review of 1,010 breast cancer patients, who had used the OCP at some point in their life, was carried out. Associations of age at OCP start with age at breast cancer diagnosis were determined by multiple linear regression analysis, considering year of birth, year of diagnosis, age at first pregnancy, number of live births, age at menarche, and length of OCP use. There was evidence of a linear trend between age at OCP start and age at breast cancer diagnosis. Women who started using the OCP aged 18 years or younger were, on average, 4 years younger at breast cancer diagnosis than women who started using the OCP over the age of 30 years, and women who started using the OCP aged 22-25 years were, on average, 3 years younger (p-value for trend <0.001). The age when the OCP was started was positively associated with the age when breast cancer was first diagnosed.