Hot flash treatment can slow breast cancer growth, trial finds

• Breast cancer is the most common cancer in women in almost all countries around the world.
• Around three-quarters of breast cancers are ER-positive, meaning that the tumors have many estrogen receptors.
• Treatment for these cancers includes anti-estrogen medication, the side effects of which, such as hot flashes, can be combated using artificial progesterones.
• Now, research has found that these artificial progesterones, even at a low dose, also slow the growth of breast tumors.

According to the World Health Organization, more than 99% of breast cancers are diagnosed in women, and less than 1% in men. And it is the most common cancer in women in 157 out of 185 countries, diagnosed in around 2.3 million women around the world each year.

Around 75% of breast cancers are estrogen-receptor positive, with tumor cells stimulated to grow by estrogen, so effective treatment includes anti-estrogen medication. However, this medication can cause uncomfortable side effects similar to those experienced during menopause, such as hot flashes, joint and muscle pain, and potential bone loss.

Now, the PIONEER trial, led by researchers in Cambridge, United Kingdom, has found that artificial progesterones, such as megestrol acetate, which help combat these uncomfortable side effects, have an added benefit — they can slow the growth of ER-positive breast tumors.

The research, published in Nature Cancer, found that when megestrol was given in addition to the estrogen-inhibitor letrozole, cell proliferation in the tumors was slowed, even at low doses of megestrol.

“These findings could have significant clinical impact by improving treatment adherence while positively impacting tumor control. However, further studies will be required to substantiate these claims.”

— Esha Sachdev, MD, breast medical oncologist, of the MemorialCare Todd Cancer Institute at Long Beach Medical Center in Long Beach, CA, not involved in the study.