Scientists are gaining a clearer understanding of why some breast cancers become far more dangerous after menopause, especially in women with obesity.
A new analysis from Georgetown University has highlighted a long‑overlooked hormone that could explain why postmenopausal women with obesity face a much higher risk of dying from the most common type of breast cancer.
This research also suggests that modern weight‑loss drugs, such as GLP‑1 receptor agonists, might one day help improve treatment for these aggressive cancers.
The focus of this new work is estrogen receptor‑positive breast cancer, often called ER‑positive breast cancer. This is the most common form of breast cancer in women after menopause, and it is also the deadliest.
According to Dr. Joyce Slingerland, a leading cancer researcher at Georgetown University’s Lombardi Comprehensive Cancer Center, postmenopausal women with obesity are not only more likely to be diagnosed with this cancer, but they are two to three times more likely to die from it.
This is alarming given that nearly half of all women in the United States are expected to be living with obesity by the end of this decade.
The hormone at the center of the problem is estrone, a type of estrogen that becomes dominant after menopause. Before menopause, the ovaries mainly produce a different estrogen called estradiol, which plays many important roles in the body. Estradiol also helps control inflammation.
After menopause, estradiol levels drop sharply, and estrone—produced mainly in fat tissue—becomes the main form of estrogen in the body. While estrone and estradiol look chemically similar, they behave very differently, and these differences matter greatly for cancer risk.
Dr. Slingerland’s research shows that estradiol can calm inflammation by blocking certain proteins that trigger inflammatory responses. In contrast, estrone does the opposite.
Her team found that estrone actually works together with inflammatory proteins to switch on genes that create and sustain inflammation. This is a problem because chronic inflammation is known to help cancer grow, spread, and become more aggressive.
In women with obesity, estrone levels can be two to four times higher in fat, breast tissue, and other parts of the body. This creates an environment where inflammation grows stronger and more persistent.
Slingerland’s earlier studies show that estrone can activate genes that push cells toward cancer. It also switches on processes that help cancer cells spread to other parts of the body. In a study with mice, estrone caused ER‑positive breast tumors to grow much faster and spread more widely than tumors exposed to estradiol.
The research team also found evidence that estrone may weaken the immune system’s ability to detect and destroy cancer cells, giving tumors even more room to grow unchecked. These findings suggest that estrone does not simply sit in the background after menopause—it actively fuels cancer development and contributes to worse outcomes for women with obesity.
Because estrone is made in fat tissue, reducing body fat may lower estrone levels and the inflammation it creates. This is why Dr. Slingerland believes that GLP‑1 weight‑loss drugs—such as Ozempic and Wegovy—could become helpful tools in treating ER‑positive breast cancer in women with obesity.
These medications have already transformed weight‑loss treatment by helping people lose significant amounts of body fat. If removing fat can lower estrone levels, then GLP‑1 medications might indirectly reduce the cancer‑fueled inflammation that estrone triggers.
Lifestyle changes like diet and exercise can also reduce weight and inflammation, but these changes can be very difficult to maintain over time. GLP‑1 drugs may offer a more reliable long‑term option for reducing estrone levels and improving outcomes.
This research, published in Nature Reviews Endocrinology, highlights an important shift in how doctors may need to think about treating breast cancer in postmenopausal women with obesity. Instead of focusing only on tumor biology, treatment may need to address the hormonal and inflammatory environment created by fat tissue.
After reviewing the findings, it becomes clear that estrone is not just a harmless hormone that appears after menopause. It may be a powerful driver of inflammation, cancer growth, and cancer spread.
The research suggests that lowering estrone—whether through lifestyle changes, medications, or new therapies—could improve survival for women facing ER‑positive breast cancer. While more studies are needed, especially clinical trials using GLP‑1 drugs in cancer patients, this new direction offers real hope for better treatment strategies in the future.
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.
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