New Study Suggests GLP-1 Drugs May Lower Breast Cancer Death Risk, But Experts Urge Caution

A new study has found that popular weight-loss and diabetes drugs like Ozempic and Wegovy may be linked to lower death rates and fewer cancer recurrences in breast cancer patients. But before you get too excited, many experts say these results might be “too good to be true.”

The research, published in the journal JAMA Network Open, looked at data from over 800,000 women with breast cancer. It found that those who took a class of medicines called GLP-1 receptor agonists had dramatically lower risks of dying from any cause over a 10-year period.

However, several cancer specialists and statisticians have raised serious concerns about the study’s methods and the quality of its data. This article breaks down what the study actually found, why experts are skeptical, and what this means for you or a loved one facing breast cancer.

What Did the Study Actually Find?

Researchers led by Dr. Bernard Fuemmeler at the Massey Comprehensive Cancer Center in Richmond, Virginia, analyzed medical records from a large U.S. database called TriNetX. They focused on women diagnosed with breast cancer between April 2006 and April 2023.

The study split patients into groups based on whether they had diabetes, obesity, or both. Here are the key numbers they reported:

• For patients with diabetes: Those who took a GLP-1 drug had a 91% lower risk of death from any cause over 10 years compared to those taking insulin or metformin. The statistical analysis showed a hazard ratio of 0.09, which is considered an extremely strong effect.
• For patients with obesity: Those using a GLP-1 drug had a 65% lower risk of death compared to those not using the drugs. The hazard ratio was 0.35.
• For breast cancer recurrence: The study reported that GLP-1 use was linked to a 56% to 67% reduction in the risk of the cancer coming back.
• Comparison with SGLT2 inhibitors: When researchers compared GLP-1 drugs to another diabetes medicine called SGLT2 inhibitors (like Jardiance), the link to lower death risk was much smaller. In an unadjusted analysis, the hazard ratio was 0.97, meaning almost no difference. After adjusting for other factors, the risk reduction was modest at 23% (hazard ratio 0.77).

The researchers called their findings “promising” and said we need more studies to understand how these drugs might help breast cancer patients.

Why Are Experts So Skeptical?

While the numbers sound amazing, several independent experts have pointed out major problems with the study. Dr. Paul Pharoah of Cedars-Sinai Medical Center in Los Angeles was blunt: “The results seem too good to be true.”

Here are the main concerns experts have raised:

• Effect sizes are unrealistically large: Dr. Pharoah noted that a 91% reduction in death risk is far beyond what any single drug has ever shown for breast cancer. To put it in perspective, the most effective chemotherapy regimens reduce the risk of cancer coming back by only about 38%. “These effect sizes simply cannot be due to the drug,” Pharoah said. “The only reasonable explanation is confounding or bias.”
• Missing key data: Dr. Mangesh Thorat of Queen Mary University of London pointed out that the database used in the study had huge gaps in important information. For example, estrogen receptor (ER) status—a critical factor in breast cancer treatment—was known for only about 20% of patients. In a well-curated dataset, this number should be close to 100%.
• Incomplete treatment information: The study lacked details on whether patients had surgery, radiation, or chemotherapy. Surgery information was available for fewer than 10% of patients. Radiation therapy data was missing for over 95% of patients. Systemic therapy (like hormone therapy or chemotherapy) information was missing for about 75% of patients.
• Real-world trials don’t match: Large, randomized clinical trials of GLP-1 drugs like semaglutide (Ozempic, Wegovy) have not shown such dramatic reductions in cancer death. If these drugs were truly that powerful, experts say, we would have seen it in those trials.

How Does This Affect You or a Loved One?

For anyone currently undergoing breast cancer treatment or supporting a family member through it, news like this can feel like a lifeline. It’s natural to wonder, “Should I ask my doctor about taking one of these drugs?”

Experts say the honest answer right now is: not yet.

Dr. Pharoah and other specialists emphasize that this study does not prove that GLP-1 drugs actually reduce breast cancer death or recurrence. The findings are what scientists call “associational”—they show a link, but they cannot prove that the drug caused the benefit.

There could be many other explanations for the results. For example, people who take GLP-1 drugs may be more health-conscious overall, have better access to healthcare, or have other factors that lower their risk. The study tried to adjust for these differences using statistical matching, but experts say the missing data makes that adjustment unreliable.

It’s also worth noting that the study only looked at women in the United States, so the results may not apply to other populations.

What Do Experts Generally Say About GLP-1 Drugs and Cancer?

GLP-1 receptor agonists were first approved in 2005 for managing type 2 diabetes. They work by mimicking a natural hormone that helps control blood sugar and appetite. In 2021, the FDA approved semaglutide (Wegovy) for chronic weight management.

These drugs have been revolutionary for diabetes and obesity treatment. They are known to help with weight loss, improve blood sugar control, and even reduce the risk of heart attacks and strokes in some patients.

However, their role in cancer treatment is still unclear. Some laboratory studies have suggested that GLP-1 drugs might have anti-inflammatory or anti-cancer effects, but these are early findings. No major cancer treatment guidelines currently recommend using GLP-1 drugs specifically to prevent breast cancer recurrence or death.

Experts generally agree that more research is needed. The authors of this study themselves called for “prospective studies”—meaning studies that follow patients forward in time, rather than looking backward at medical records—to understand the potential risks and benefits.

Practical Takeaways for Readers

So, what should you do with this information? Here are some practical steps:

• Don’t change your treatment plan: If you or a loved one is being treated for breast cancer, do not stop or start any medication without talking to your doctor first. This study does not provide enough evidence to change standard care.
• Ask informed questions: If you have diabetes or obesity and are already taking a GLP-1 drug, it’s reasonable to ask your oncologist if there might be any additional benefits for your cancer. But understand that the evidence is very preliminary.
• Focus on proven treatments: The most effective ways to reduce breast cancer recurrence and death are still standard treatments like surgery, radiation, chemotherapy, hormone therapy, and targeted therapies. Lifestyle factors like maintaining a healthy weight, exercising, and not smoking also play a role.
• Watch for future studies: The authors of this study have called for more rigorous research. Keep an eye on news from trusted sources like the American Cancer Society or the National Cancer Institute for updates.
• Understand study limitations: Remember that a single study, especially one with major data gaps, is not enough to change medical practice. Science works by building evidence over time through multiple studies.

The Bottom Line

This study raises an interesting question about whether GLP-1 drugs like Ozempic and Wegovy might help breast cancer patients live longer. But the results are so dramatic—and the data so incomplete—that most experts are not convinced.

Dr. Pharoah summed it up well: “The biggest red flag is that the effect sizes are enormous.” Until we have better-designed studies that fill in the missing information and confirm these findings, patients and doctors should treat this news with healthy skepticism.

For now, the best advice remains: work closely with your healthcare team, follow your prescribed treatment plan, and stay informed as new research emerges. GLP-1 drugs may someday play a role in breast cancer care, but we are not there yet.

Source: MedPage Today