GLP-1s and Cancer Part 3 - The Guardian Article

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In part 1 we discussed the basics around the current studies considering possible impacts of GLP-1s on cancer (if you haven’t read part 1 yet you might want to as I will refer to the things discussed in that post.) In part 2 we looked at a study that explored correlation between GLP-1 use and cis women with breast cancer. Today we’re going to look at a Guardian Article that many of you asked me to discuss. This piece got way too long so I’ll discuss the article in general in Part 3 and the studies they refer to in the final installment in this series in Part 4.

As I read through this article, as well as other media articles and social media posts that so many of you sent me about this topic, one thing I noticed was that a number of the studies that were mentioned were not yet published in a peer-reviewed journal, instead having been presented at a conference. There is nothing wrong with conference presentations and they can even be used to improve an article for publication if those in attendance offer helpful feedback. That said, I would suggest that writing media articles and creating social media posts about the findings of studies that haven’t been peer reviewed and published, at least without being very clear about that, is irresponsible. Peer review, especially around studies about weight and health, is certainly not the end all and be all and is subject to reviewer bias, but lack of publication also means that these outlets and influencers are putting their faith in the abstracts of studies whose complete methodology and findings are not available to be analyzed. These studies may well have been presented by someone with financial interest in the results (which can often be found and, if so, should always be disclosed) at a conference sponsored by a company/companies with financial interest in the results (which can also often be found and should be disclosed). So if you are reading articles about this (or really any topic) and you can’t find the actual published study (sometimes, but not always, the article will say something like “the study, that was presented at [name of conference]), know that, at the very least, there are a lot of question marks.

Let’s get into this Guardian Article:

The article is called “Weight-loss drugs can cut breast cancer risk by up to 30%, studies suggest” and we’re going to start right here.

I would say that this title is irresponsible at best. They’ve covered their proverbial ass by using the phrase “studies suggest” but even that is an overstatement. It’s a stark reminder that the ability of online media to survive is based on clicks and interaction and a headline that said “Studies with significant limitations show some associations between GLP-1s and breast cancer risk but we’re many studies away from knowing anything conclusively” does not have the same power to generate those coveted clicks.

The subtitle is “Three studies add to evidence that jabs could be part of cancer-fighting toolkit to cut risk of developing or dying from disease.”

Here again we have the CYA with “could be” but “add to the evidence” is a stretch here. There is, as of yet, no causal evidence. There are only possible links based on studies with methodologies that are limited. Significant further research is required to show that GLP-1s have any impact on any of the many types and subtypes of cancer.

The premise of the article is outlined in the first line:

“Weight-loss drugs can cut the risk of developing or dying from cancer by 30%, doctors have said.”

WHAT?! What doctors said this?

Also, GLP-1s were, first and foremost, approved as Type 2 diabetes drugs with a small side effect of weight loss. Later it was found that in megadoses they can cause a bit more (temporary) weight loss. Most of the studies of GLP-1s and cancer don’t even track what drug or dose people are taking. So why are GLP-1s being repeatedly characterized by this article as “weight loss drugs”?

Getting back to the question of what doctors said this…

The article quotes Dr Elizabeth McDonald, a professor of radiology at the University of Pennsylvania and a breast radiologist at the Abramson Cancer Center.

“While our study was observational and does not definitively confirm an association between GLP-1 medications and reduced breast cancer incidence, it does add to the growing body of evidence suggesting that it’s worth investigating these weight-loss drugs as potential cancer prevention tools.” (emphasis mine)

That is a far, far cry from saying these drugs “can cut the risk of developing or dying from cancer by 30%.”

In further quotes Dr. McDonald seems to be making assumptions that weight loss is what is driving the difference in cancer outcomes despite her study (and others as well) not showing a cause and effect relationship and not tracking what drug people were on, what dose they were taking, how much weight, if any was lost, and if weight loss was even correlated to the correlational findings. This is the kind of thing doctors, researchers, and everyone else, should avoid doing.

So what other doctors do they quote?

“Dr Marcin Chwistek, the director of the supportive oncology and palliative care programme at Fox Chase Cancer Center in Philadelphia, who was not involved with the research, said:

“GLP-1 receptor agonists have never been just glucose-lowering drugs. Their anti-inflammatory and immune-modulatory properties have long suggested broader effects.”

Importantly, links have been found to anti-inflammatory or immune-modulatory properties and mechanisms of action have been postulated, but these are not proven and causal mechanisms are not fully understood. Similar to the research around cancer, the effects of these drugs are constantly subject to the “there’s so much evidence” fallacy where correlational evidence is pumped out and unproven claims are repeated as if they are fact until they reach “everybody knows” status. Just like the drugs’ actual impact on Type 2 Diabetes, these claims might have actual health benefits if they are true, but here again, we would need trials creating information about what drug(s), at what dose, for what effect, with what side effects etc. Even with all of this, this doctor’s quote doesn’t come close to supporting the article’s claim that “doctors have said” that these drugs “can cut the risk of developing or dying from cancer by 30%”

Finally they quote Dr Eleonora Teplinsky, who “was not involved in the research” (for those playing the home game, the author of the Guardian article quoted three doctors, two of whom weren’t even involved in the research) and is “the head of breast and gynaecologic medical oncology at Valley Health System in New Jersey”

The Guardian themselves characterize Dr. Teplinksy as saying “I think there is enough data to show there is clearly some impact on either cancer risk or the risk of recurrence, but we haven’t yet defined it exactly,” she said. “We need to do more studies putting patients on them and seeing what happens.”

This quote is a mess - she thinks there is “enough evidence” for one outcome OR another outcome? Usually if there is “enough evidence” for something we know what it is! (Also, this is what I mean by the “there’s so much evidence” fallacy that I talked about in Part 1.) I also think it’s worth noting that, per OpenPayments, between 2018 and 2024 she took over $281,093.44 in associated research funding from Eli Lilly and $316,300 from Pfizer which has a GLP-1 in active development. Regardless, this quote also does not support the claim made in the first sentence of the article.

So they start the article by saying that these drugs “can cut the risk of developing or dying from cancer by 30%, doctors have said” and then they quote exactly zero doctors who have said that.

Spoiler alert - this article does not offer one doctor who says what they claim that doctors (plural) have said.

What they do offer is a brief, very rosy picture of three studies, two that haven’t been published and one that was accepted by the journal so recently that the final draft isn’t even published. So what did these studies find? We’ll talk about it in Part 4.

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*Note on language: I use “fat” as a neutral descriptor as used by the fat activist community, I use “ob*se” and “overw*ight” to acknowledge that these are terms that were created to medicalize and pathologize fat bodies, with roots in racism and specifically anti-Blackness. Please read Sabrina Strings’ Fearing the Black Body – the Racial Origins of Fat Phobia and Da’Shaun Harrison’s Belly of the Beast: The Politics of Anti-Fatness as Anti-Blackness for more on this.