A new clinical trial from the University of Cambridge has found that a hormone-like drug could help fight breast cancer while also making treatment easier for patients.
The drug, called megestrol acetate, is a man-made version of the hormone progesterone. It is already used to help reduce hot flashes in women taking anti-estrogen treatments for breast cancer.
Now, researchers have discovered that megestrol may also help stop tumors from growing when combined with standard breast cancer therapy.
About 75% of breast cancers are known as ER-positive. This means they grow by using estrogen, a natural hormone in the body. To treat this kind of cancer, doctors often give patients anti-estrogen drugs that lower estrogen levels and slow the cancer’s growth. One common anti-estrogen drug is letrozole.
But while these drugs are effective, they can cause side effects like hot flashes, joint pain, and bone loss. These problems can make it hard for some women to continue their treatment.
The new study, called the PIONEER trial, looked at whether adding low doses of megestrol to letrozole could improve results for patients. Nearly 200 women from 10 hospitals in the UK joined the study. They were split into three groups.
One group took letrozole only. The second group took letrozole with 40 mg of megestrol. The third group took letrozole with 160 mg of megestrol. All women received their assigned treatment for two weeks before having surgery to remove their tumors.
The researchers found that women who took both letrozole and megestrol had slower tumor growth than those who took letrozole alone.
Surprisingly, the lower dose of megestrol worked just as well as the higher dose. Since higher doses can cause side effects like weight gain and high blood pressure, this result is especially important.
The findings were published in the journal Nature Cancer. They suggest that using a low dose of megestrol could improve how well anti-estrogen drugs work, while also helping patients avoid difficult side effects. Because megestrol is an older, off-patent drug, it is also a low-cost option that could be more widely available.
This study builds on earlier lab research that showed progesterone can slow down the growth of ER-positive breast cancer cells. In those experiments, adding progesterone helped stop cancer cells from dividing. The new trial confirms that this effect also happens in real patients.
The study was led by Dr. Richard Baird and Professor Jason Carroll. They say the results offer hope for improving treatment without making it harder for patients to stay on their medications.
However, the trial only lasted two weeks, so more research is needed to see if megestrol continues to work over a longer period. Follow-up studies will also look at whether low doses still help slow cancer growth and prevent side effects if taken for many months or years.
Still, the early results are promising. If future research supports these findings, doctors may have a new, affordable way to improve care for thousands of women with breast cancer.
If you care about breast cancer, please read studies about a major cause of deadly breast cancer, and this daily vitamin is critical to cancer prevention.
For more information about cancer, please see recent studies that new cancer treatment could reawaken the immune system, and results showing vitamin D can cut cancer death risk.
The study is published in Nature Cancer.
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