A full-term pregnancy at an early age is the only natural physiological condition known to significantly decrease the lifetime risk of breast cancer in women of all ethnicities worldwide. Results of this study showed that when administered one microgram of estradiol per day for three weeks, rats that had not previously borne offspring had no mammary cancers nine months after being injected with chemical carcinogens.

"We found that daily sustained treatment with pregnancy levels of estrogen for three weeks is a simple, safe, short-term, inexpensive procedure for hormonal prevention of mammary cancer," according to Rajkumar Lakshmanaswamy, research assistant in the cancer research laboratory and lead investigator of the study which was conducted in Nandi Laboratory at the Cancer Research Laboratory, University of California at Berkeley. "This procedure is as effective as full-term pregnancy, removal of the ovaries or long-term tamoxifen treatment, without any loss of ovarian function including the potential for future successful pregnancies and lactation."

Full-term pregnancy in humans, as well as rats, results in a long-term decrease in blood levels of growth hormone and prolactin, resulting in a reduced promotional environment for development of breast cancer. The study was conducted in rats that had never borne babies, to test the duration and level of estradiol needed to induce protection against carcinogen-induced mammary cancer.

"The study concluded that this treatment can be used as a paradigm for developing strategies for human breast cancer prevention," said Dr. Lakshmanaswamy.

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Contact: Aimee Frank
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American Association for Cancer Research
15-Oct-2002