SCIENCE / CANCER : Contraceptive Shows Promise in Reducing Breast, Ovarian Tumors

A new type of contraceptive that could reduce breast and ovarian cancer has shown promise in early studies, USC researchers reported Tuesday.

In a pilot study, 14 Southern California women who are at high risk for breast cancer received a mixture of hormones to prevent pregnancy, including a much smaller dose of estrogen than normally used in oral contraceptives. Estrogen is linked to the development of breast cancer.

All of the women responded well to the contraceptive and none has become pregnant, said Malcolm C. Pike, who is a co-director of the study, along with Dr. Darcy Spicer. It’s too soon to observe reductions in cancer in the women, but the USC researchers predict that they have achieved a balance of hormones that will reduce cancer rates.

Research shows that traditional oral contraceptives--composed of synthetic versions of estrogen and progesterone--reduce the risk of ovarian cancer by stopping ovulation.

“A woman taking oral contraceptives for six years will have a 50% reduction in risk for ovarian cancer,” said Pike, who presented his findings at a meeting of the General Motors Cancer Research Foundation in Boston. “That’s a well-established effect of oral contraceptives. This is a pretty wonderful thing,” he said in a telephone interview. However, the presence of estrogen in oral contraceptives increases the risk of breast cancer for reasons that are not well understood, Pike said.

The combination being tested at USC continues to reduce the ovarian cancer risk by blocking ovulation and shutting down the ovaries with a third hormone called gonadotropin-releasing hormone agonist, or GnRHA. Only enough estrogen and progesterone are added to replace what is normally made by the ovaries.

“If you want to prevent cancer of the breast, you need to reduce the dose of estrogen and progesterone,” Pike said. The two hormones, he said, “can be reduced by 50% (of that currently used in oral contraceptives). It’s that reduction in dose that we believe will reduce cancer risk. It’s really a very low-dose pill.”

The hormone combination currently under study may need to be adjusted to protect against bone loss because reducing estrogen can accelerate bone loss, Pike said.

“Our preliminary results suggest that we don’t have it quite right. But we’re close,” he said.

Another problem with the method is that the GnRHA is administered through monthly injections. The USC team has begun discussions with pharmaceutical industry representatives to develop the contraceptive using a different type of drug delivery, perhaps a longer-acting injection or a patch or intravaginal ring.

“What we are hoping initially is to develop a single injection that you’d get every four months that would have all the components to it,” Pike said. “We need contraceptives, and women need different choices. I hope this will become an option in time.”