A HORMONAL CONTRACEPTIVE APPROACH TO REDUCING BREAST AND OVARIAN-CANCER RISK - AN UPDATE

Epidemiological studies have consistently found that bilateral oophore ctomy at a young age substantially reduces breast cancer risk. Such su rgical menopause around age 35 has been found to reduce risk by 60 to 75%. A reversible medical oophorectomy using an agent such as a gonado tropin-releasing hormone agonist (GnRHA) should achieve a similar redu ction in risk. Although the use of GnRHA alone is unacceptable because of the associated hypoestrogenic side-effects, these can be satisfact orily prevented by add-back low-dose estrogen treatment with intermitt ent progestin to protect the endometrium. It is estimated that a regim en of GnRHA plus add-back ultra low-dose estrogen and progestin would prevent some two-thirds of current breast cancer if used from age 30. If used from age 20 almost nine out of ten current breast cancer cases would be avoided. If, as is likely, these estimates also apply to wom en at high genetic risk of breast cancer because of possession of a BR CA1 or BRCA2 gene, their breast cancer risk would be reduced to below that of 'normal' women. The protective effects on ovarian cancer are c alculated to be greater than the protective effects on breast cancer. Practical chemoprevention of breast and ovarian cancer using this appr oach should be possible within 5 years.