AMNA NAWAZ: A growing body of research suggests popular weight loss drugs like Ozempic and Wegovy may also help treat or prevent certain cancers.

It's the latest unexpected benefit to be associated with GLP-1s, which are now taken by one in eight American adults.

William Brangham has more.

WILLIAM BRANGHAM: The results in these cases come from what are known as observational studies, not more rigorous clinical trials, and researchers say there are still many open questions.

That said, this was the hot topic at a recent conference of America's top cancer doctors, where a number of observations all pointed in the same direction, that GLP-1s appeared to help fight cancer above and beyond the benefits that you would expect from weight loss alone.

So, to understand these implications and the limitations of these studies, we turn to Dr.

Neil Iyengar.

He's director of breast oncology and cancer survivorship at the Winship Cancer Institute at Emory University.

Dr.

Iyengar, thank you for being here.

There is this growing body of observational evidence that GLP-1s do seem to help with regards to cancer.

Big picture, what have those studies found?

DR.

NEIL IYENGAR, Emory University School of Medicine: Well, thanks for having me.

I think this is really exciting and important data.

We have known for a very long time that obesity is associated with an increased risk of at least 13 different cancers, possibly 20 different cancers.

And so reversing obesity has been a key area of research.

Up until now, we haven't had powerful methods for weight loss as we do with the GLP-1 receptor agonists.

These studies that you have pointed out really identify an exciting hypothesis or theory.

And I say that because, as you mentioned, these are observational studies.

But the data really support the idea that weight loss through a GLP-1 receptor agonist cannot only help to prevent many of the obesity-related cancers, but may actually help to prevent a recurrence of some of these cancers even after a cancer diagnosis.

WILLIAM BRANGHAM: I mean, it's quite striking.

I just want to read some of the details from some of these studies.

One analysis from the University of Pennsylvania found women between the ages of 45 and 80 who were taking these drugs were about 30 percent less likely to develop breast cancer than those who were not.

Another surveyed patients identified with seven types of early-stage cancer and found GLP-1s significantly reduced the risk of spread in four of them, lung, breast, colon, and liver cancers.

Again, do you believe that this is principally a function of weight loss being the real actor here?

DR.

NEIL IYENGAR: I do.

It's been clear from prior studies where we have used methods like diet or exercise, which induce lower amounts of weight loss.

But even at those lower-levels of weight loss, we see some reduction, not as profound as what you have just read, but we see some reduction in the risk of obesity-related cancers.

What we do know from studies that have looked at larger weight loss procedures, like bariatric surgery, for example, is that the more weight loss we can induce in people who are struggling with obesity, the lower the risk of developing cancer or cancer recurrence.

So it's not surprising that, when we look at these large observational data sets, a GLP-1 receptor agonist, which can typically induce 15 to 20 percent or even greater weight loss, similar to what bariatric surgeries do, that these drugs can also reduce the risk of cancer.

And it does seem that it's primarily through the weight loss function.

We also know that GLP-1s have some anti-inflammatory effects as well.

And we're learning about some possible immune-related effects as well.

But I think it's really driven through the large amounts of weight loss that these drugs can induce, as opposed to prior or other diabetes drugs.

And that's where we're probably likely to see success with the GLP-1s and cancer risk reduction.

WILLIAM BRANGHAM: So let's say those studies go forward and they do show this real effect.

How much of a shift would this be in your field of cancer, in oncology?

DR.

NEIL IYENGAR: I think that we are standing really at the precipice of a massive possible shift in the global health burden, not only of obesity, but obesity-related cancers.

We know that one in seven male cancer-related deaths and one in six female cancer-related deaths are related to obesity.

If we can reduce the obesity problem, which we know we can do with the GLP-1s, this really stands to remarkably shift the global burden of obesity-related cancers.

But we have to do this cautiously, because there are mixed data for the effects on various types of cancers, interactions with different types of cancer therapies.

This is why it is so essential that we continue studying these drugs in a prospective, rigorous way, so we can optimally and safely use them to reduce cancer burden.

WILLIAM BRANGHAM: I mean, given what we know now - - you're a specialist in treating breast cancer.

Again, with the data that we have currently, would you suggest to your patients that they take a GLP-1 either for current cancer patients or as a preventative?

DR.

NEIL IYENGAR: I think this is a tricky question right now, because this is where we have to rely on the available data, which is observational, as we've been discussing.

And so where I worry is, we don't have data on how the GLP-1s may or may not interact with cancer therapies.

So, for a patient who has completed their cancer therapy and is cancer-free, I think, if they are dealing with obesity, then this could be a successful approach for, A, reducing obesity, and, B, reducing the risk of cancer recurrence due to obesity.

But for patients who are currently on treatment, especially chemotherapy or immune therapy, we don't know yet precisely how these drugs may interact.

They may possibly make side effects worse.

They may possibly make some treatments like immunotherapy less effective for cancer treatment.

That's really where we don't know enough to recommend the use of a GLP-1 in that setting.

So, ultimately, I would say, for a cancer survivor who has completed their therapy and is struggling with obesity, it is worth having that discussion with your oncologist and with your doctors about whether it is safe to use a GLP.

But if you're on active therapy, certainly, have that conversation with your oncologist.

I would caution against it until we generate more data.

WILLIAM BRANGHAM: All right, that is Dr.

Neil Iyengar of Emory University.

Thank you so much for being here.

DR.

NEIL IYENGAR: Thank you for having me.