Association of hormonal and reproductive risk factors with breast cancer in Indian women: A systematic review of case-control studies

The incidence of breast cancer in India has seen a rapid increase in recent years. Hormonal and reproductive risk factors for breast cancer have been affected by socioeconomic development. Studies on breast cancer risk factors in India are limited by the small sample size and specific geographical area. The current systematic review was carried out to assess the association of hormonal and reproductive risk factors with breast cancer in Indian women. A systematic review of MEDLINE, Embase, Scopus, and Cochrane database of systematic reviews were done. Relevant case-control studies published in peer-reviewed indexed journals were analyzed for hormonal risk factors such as age at menarche, menopause, and first childbirth; breastfeeding; abortion; and oral contraceptive pills use. Younger age (<13 years) at menarche was associated with high risk (odds ratio 1.23-3.72). Other hormonal risk factors with strong association were age at first childbirth and menopause, parity, and duration of breastfeeding. Abortion and the use of contraceptive pills did not have a clear association with breast cancer. Hormonal risk factors have a higher association in premenopausal disease and estrogen receptor-positive tumors. There is a strong association between hormonal and reproductive risk factors and breast cancer in Indian women. The protective effect of breastfeeding is related to the cumulative duration of breastfeeding.