CAMBRIDGE, Mass., July 9 (UPI) -- About half of women with breast cancer could have an improved prognosis if progesterone is added to their treatment, according to a new study.
Cancers with progesterone receptors are known for growing more slowly, however scientists have not been able to exploit this fact until they discovered the way they interact with estrogen, which causes the growth of some tumors.
"This important laboratory research helps explain why some breast cancer patients have a better outlook," said Dr. Jason Carroll, of the Cambridge Research Institute, in a press release. "Crucially, it provides a strong case for a clinical trial to investigate the potential benefit of adding progesterone to drugs that target the oestrogen receptor, which could improve treatment for the majority of hormone-driven breast cancers."
Estrogen-fueled tumors are often treated with tamoxifen, which blocks receptors for that hormone. In the new study, researchers found that progesterone receptors interact with estrogen receptors in the tumor, changing their behavior and slowing the tumor's growth.
Roughly 75 percent of women with breast cancer have tumors with the estrogen receptor, and 75 percent of those tumors also have progesterone receptors -- suggesting more than half of these patients could benefit if the treatment is shown to be successful.
"It appears you control the tumors better, but to prove it is better in women with breast cancer we need to do the trial," which Carlos Caldas, a professor at the University of Cambridge, told the BBC is in the planning process right now. "It could be very significant. In early breast cancer you could increase the number of people being cured and in advanced breast cancer, where we're not curing, we could control the disease for longer."
The study is published in Nature.