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More subterfuge on subgroup analysis … this time from a major cancer organization


3 Star

Metformin may lower lung cancer risk in diabetic nonsmokers

Our Review Summary

iStock_000033186898_SmallThis release reports on an NIH-funded study to determine if the use of the drug metformin by diabetic patients may affect their risk of developing lung cancer. The overall answer is that it does not, but the release takes five paragraphs to say that. Instead, it focuses on a very small subset of patients who had never smoked and whose lung cancer risk appeared to be lower than never-smokers who didn’t take metformin. By trumpeting findings from that subgroup — and burying the main results of the study, which were negative — this release misrepresents the research findings and misleads its readers.

We’d suggest that the findings of this study probably did not warrant the spotlight provided by a news release. But if a news release is to be issued, it should lead with the results for the primary outcome and give second billing to provocative but preliminary findings from subgroups. While not as egregious as another example of subgroup “spin” that we recently reported on, this news release will certainly give readers the impression that there’s something special about metformin when it comes to preventing cancer in people with diabetes, when that hasn’t been established with any certainty.


Why This Matters

Diabetes is a chronic disease requiring long-term use of drugs such as metformin. Some research suggests that metformin may decrease the risk of lung cancer — making the results of this study an important addition to the scientific literature. Unfortunately, the release focuses almost entirely on the results seen in a small subgroup of patients. As such, it doesn’t accurately reflect the totality of the research in question. Subgroup findings can be included, but should never supersede the main outcome.


Does the news release adequately discuss the costs of the intervention?

Not Satisfactory

There is no discussion of the cost of metformin, which is available as a generic and is comparatively cheap. Nevertheless, since diabetes often requires a lifetime of drug use, costs of metformin versus other drugs would be useful to readers, especially in cases such as this when the drug under study is suspected of providing additional benefits or bringing negative side effects.

Does the news release adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

We appreciate that the release attempts to quantify the reduction in risk associated with metformin use. However, there’s a problem with the release’s description of these results. The research paper points to a statistically significant reduction in lung cancer risk only among diabetic patients who have never smoked. But the release generalizes this finding to all “nonsmokers.” The release doesn’t delineate between people who have never smoked and those who did smoke but quit. The benefits appear to apply only to the group of never smokers. This is an important distinction.

Does the news release adequately explain/quantify the harms of the intervention?

Not Satisfactory

There is no mention in the release about potential harms that may arise with the administration of metformin. The drug is known to produce harmful side effects in more than 10 percent of people taking it, largely affecting the stomach or bowel such as vomiting, diarrhea, and loss of appetite.

Does the news release seem to grasp the quality of the evidence?

Not Satisfactory

Our concerns about the treatment of evidence start with the headline: “Metformin may lower lung cancer risk in diabetic nonsmokers.” Since this is an observational study that cannot prove cause and effect — only associations — we think the use of an active verb here (“may lower risk”) is inappropriate. The release should have said that metformin is “linked with” or  “associated with” lower risk, but not that it “lowered” risk. We offer a primer on this issue for health writers here.

The release does provide considerable data derived from the actual research paper, compared to many such releases, but then points to the lack of statistical significance for that data.  Releases are intended to simplify and clarify research so that general readers can understand the importance of the findings.  In this case, the release centers on a minor finding that applies to only a small subset of individuals in the study while mentioning the larger overall findings in passing. (The finding of “decreased risk” is based on just 80 people in the study who developed lung cancer despite never smoking.) That overall finding — that metformin generally has no effect on lung cancer risk — hardly qualifies as news. The decision to do a news release on this study at all is questionable.

Does the news release commit disease-mongering?


The release does not commit disease-mongering.

Does the news release identify funding sources & disclose conflicts of interest?


The release clearly identifies the funding source for the research and also adequately discloses conflicts among the authors of the paper.

Does the news release compare the new approach with existing alternatives?

Not Satisfactory

The release investigates the possibility that metformin may decrease the risk of lung cancer in people who never smoked. This would have been an opportune place to add that not smoking — or quitting smoking, if you are a smoker — is probably the most important thing one can do to reduce the risk of lung cancer.

Does the news release establish the availability of the treatment/test/product/procedure?


The story does not directly address the availability of metformin. However, it’s apparent that the drug is available, since thousands of people in the study have been taking it for years.

Does the news release establish the true novelty of the approach?


The release does reference earlier research that offered conflicting findings and supports the need for this larger study.

Does the news release include unjustifiable, sensational language, including in the quotes of researchers?


The release is cautious in its choice and use of language in explaining the current research.  It is troubling, however, that a small aspect of the research’s findings is the main emphasis of the release, while the research paper itself keeps that aspect in proper perspective.

Total Score: 5 of 10 Satisfactory


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