Estrogen and androgen levels in women treated with radiation for cervical cancer--possible influence on breast cancer risk.

In 1984-1985, estrogen and androgen levels in blood sera were measured in 320 women who had been treated for cervical cancer in the early 1960s. Study subjects were from US clinics in Baltimore, Maryland; Boston and Norfolk, Massachusetts; Buffalo, New York; Houston, Texas; and San Juan, Puerto Rico. These clinics had participated in a larger international follow-up study of cervical cancer in which a 20-30% reduction in breast cancer risk was linked to prior pelvic irradiation, even when treatment occurred after menopause. Overall, the 203 irradiated and 117 nonirradiated women had similar mean levels of estradiol, estrone, androstenedione, and testosterone. However, there appeared to be negative, albeit inconsistent, trends for androstenedione, testosterone, and estrone, suggesting that the irradiated women had lower levels of these hormones when compared with the nonirradiated women. These differences did not reach the level of statistical significance. While chance could partially explain these findings, it is plausible that the frequently observed protective association of breast cancer with pelvic irradiation could be due in part to a decrease in steroid hormones that is secondary, perhaps, to adrenal irradiation.