Oral contraceptives and breast cancer

Breast cancer is one of the leading causes of cancer death in women worldwide accounting for around 25% of all cancers. The aetiology of breast cancer is multifactorial and cannot be directly attributed to any single factor.

Out of the multiple factors involved in the development of breast cancer, many are related to exogenous or endogenous estrogen exposure. Nulliparity (having no children), early onset of menarche, delayed first birth, late menopause, oral contraceptives, hormone replacement therapy and decreased parity are few of the known risk factors of breast cancer which expose females to an increased endogenous estrogen level.

Oral contraceptives have revolutionized the reproductive lives of millions of women since their introduction in the 1960s. OCs are hormone-containing medications that are used to prevent unwanted pregnancy. They. Over 300 million women take OCs every day worldwide. However, according to some studies, there was an increase in the incidence of cervical and breast cancers with use of oral contraceptive pills.

Breast tissue is rich in estrogen receptors (ER) and progesterone receptors (PR) which when stimulated by estrogen and progesterone hormone lead to proliferation, differentiation and apoptosis of breast glandular tissue. Exogenously administered steroid hormones present in OCs can cause abnormal proliferation of breast tissue due to stimulation of these growth receptors

Different studies show conflicting results but a majority show a positive association of oral contraceptive use and breast cancer development.

According to a study in 2018, the use of oral contraceptives had a significant association with breast cancer development and doubles the risk of breast cancer. Women who are long term users of oral contraceptives are at increased risk for developing breast cancer than those who never used it.

Every use of oral contraceptives increases the risk of breast cancer by 2.77 times than the non-users. In a study in 2013, carried out in AIIMS, the risk of breast cancer was 9.5 times higher in women who had a history of use of oral contraceptives.

Another study states that women who use oral contraceptives need to attend regular cancer screening and preventive programs. The risk for breast cancer may be higher in women having a family history of breast cancer or BRCA mutation. In women with a BRCA1 mutation, the genes have already failed to perform the tumour-suppressing function and further increase in estrogen and progesterone levels may stimulate abnormal breast cell proliferation leading to the development of breast cancer.

The risk of breast cancer is related to the duration of use of hormonal contraceptives. In women who have used contraceptives for a shorter duration, results show a rapid reduction of the risk on discontinuation, whereas, for women who have used contraceptives for a longer duration, the risk might persist for at least five years, even after discontinuation.

In women younger than 40 years of age, the relative risk of development of triple-negative breast cancer was 4.2 times, with oral contraceptive use for more than a year. According to an analysis, the usage of oral contraceptives was found to increase the risk of pre-menopausal breast cancer especially with use before the first full-term pregnancy.

The patients who had used high dose contraceptive pills with a high dose of estrogen are at increased risk than patients who used low dose pills. Different formulations of oral contraceptives might convey different risks of breast cancer. Triphasic preparation with levonorgestrel as progestin was found to have a higher risk. Recent use of OCs containing high dose estrogen was associated with increased breast cancer risk when compared to no use or former oral contraceptive use.

The risk of breast cancer is significantly elevated in women using oral contraceptives. Risk is higher in women with current or recent use and also increases with duration of use. For long-term users of oral contraceptives breast cancer screening every six months is warranted. Women using contraceptive pills should be aware of the risks involved.

Tests like Mammography and Thermalytix can detect cancerous changes in the breast much before symptoms appear. Regular screening with such tests helps in close monitoring of breast health in high-risk women.

(The writer is a consultant oncologist)