When TV networks lead with a health care study – as NBC did last night – my antenna are up looking for caveats. NBC anchorman Brian Williams opened like this:
“We are going to begin here tonight with a story from the world of medicine that could end up affecting every American. This is a story about cancer, its treatment and prevention, and this time it’s a story about aspirin. It is without question the cheapest medication in the American household. Its role in preventing heart disease and strokes is well documented. We call it the wonder drug. But this is about something else. It’s new evidence tonight having to do with the role aspirin plays in preventing certain kinds of cancers.”
Framing…emphasis…elements put into a story and left out.
But the research is not conclusive and did not prove that aspirin combats cancer.
And HealthDay later reported:
While the study is attention-getting, not everyone agrees with the overall conclusions.
Among them is Nancy R. Cook, an associate biostatistician at Brigham and Women’s Hospital and Harvard Medical School in Boston and co-author of an accompanying journal editorial. She pointed out that these studies only dealt with trials where aspirin was given daily, whereas two large trials in which aspirin was given every other day found no connection with cancer prevention.
“Aspirin seems to work for people who have had cardiovascular disease. Perhaps in the long-term it will turn out to be protective for cancer, but we need to verify that and get more information,” Cook said.
The Reuters London story went out of its way to point out that aspirin was originally developed by Bayer, but didn’t note, as MedPage Today did, that:
(one author) disclosed relationships with AstraZeneca, Bayer, Boehringer Ingelheim, sanofi-aventis, Bristol-Myers Squibb, and Servier. Co-authors disclosed relationships with AstraZeneca, Bayer, sanofi-aventis, and Bristol-Myers Squibb.
The MedPage Today story also added this context:
Despite the comprehensive nature of the analyses, they did not include the two largest clinical evaluations of aspirin’s effect on cancer risk, noted authors of a commentary published simultaneously in The Lancet. The Women’s Health Initiative and the Physicians’ Health Study involved more than 60,000 men and women, and neither demonstrated an effect of aspirin on cancer risk.
“…of the new and old aspirin data with respect to its effects on cancer and cardiovascular complications in the context of a heightened risk for bleeding. The review is full of fabulous information about what we know and the uncertainties that remain, all with practical suggestions at the end.”
But she also points to a possible selection bias:
“…(which) may very well mean that aspirin’s role is not as a cancer prevention, but more likely as a sort of a stress test for those with a subclinical cancer. So we are left again with the the chicken-and-egg question. But isn’t that, after all, what makes science exciting?”
I encourage you to read her analysis.
Addendum on March 22: Another noteworthy post – “The Lancet and aspirin and all cause mortality,” by Margaret McCartney.