An epidemiological assessment of increasing incidence and trends in breast cancer in Mumbai and other sites in India, during the last two decades.
Changes in endogenous hormones at various times in life (e.g., early menarche, birth of the 1st child at an advanced maternal age, and late menopause) increase the changes of developing breast cancer. It is reasonable then to expect oral contraceptive (OC) use to increase the risk of breast cancer. It is difficult, however, to prove OC exposure has this effect due to changed OC use patterns plus OCs consist of many different hormones at various doses and compositions. Yet, OC use in the past (even more than 15 years of OC use) had not increased the risk of breast cancer in women of all combined age groups. 3 research groups have identified a small increase in overall risk in low risk women, but unidentified sources of bias or confounding could account for this increased risk. Some recent studies indicate an increased risk of breast cancer with duration of OC use, but the risk depends somewhat on dose of either the estrogen or the progestin. Nonetheless, these findings were weak and inconclusive. Other research shows long-term OC use increases the risk of breast cancer in just young women (under 45 years old). Future epidemiologic studies thus need to address increased breast cancer risk in women under 45 years old who used OCs for a long time. They need to look at whether the risk is due to early use and continues into older age or to longterm use at any time in just young women. Some studies should include women with and without various biological markers of susceptibility. Other studies should measure blood levels of estrogens and progestins in women using the same OCs. BAsed on the information now available, it would be unwise for physicians to warn women against using the highly effective OCs because they do prevent unwanted pregnancy and are protective against ovarian and endometrial cancer.