The Apoquel study results posted here raise a lot of questions. Evidence of a correlation cannot be assumed to be causality. (For anyone who wants to understand more about that premise, I
highly recommend reading
Freakonomics, for some fun summer reading that's accessible and enjoyable for non-math/science types--any public library will have it on the shelves).
This short video helps explain the general idea:
https://www.youtube.com/watch?v=lbODqslc4Tg
And this one is a little better:
https://www.youtube.com/watch?v=t8ADnyw5ou8
The mere presence of dogs who got cancer alone in the Apoquel study group doesn't tell us enough to know the relationship between the drug and the cancers. Causation is extremely tricky to show with cancer, especially multiple kinds of cancer, as here. There
could be causality from a drug. Or it
could also just be nothing more than statistical "noise."
Things I'd like to know include:
-Age of the dogs in the study who developed cancer (cancer is a leading cause of death in dogs, with about half of all of them dying of it, so we would expect a large number of older dogs in
any group to die of cancer).
-Breeds of the dogs who developed cancer (and possibly even the lines they came from), because some cancers (including hemangio) appear likely to be genetic, or at least have a significant genetic component. For example, if the splenic tumors developed in pb Golden Retrievers and German Shepherds from certain showlines where a strong majority of the dogs for several generations have died of hemangio...then those dogs in the study most likely would have died from that cancer no matter what.
-Prior environmental exposures to known carcinogens also ought to be controlled for in the statistical analysis. One example would be farm dogs exposed to heavy loads of farming pesticides and herbicides known to be carcinogenic. Another example would be skin cancers in certain light-coated breeds where the dogs have spent a lot of time in their lives outside, exposed to the sun.
-Most intriguingly, I'd like to know whether itchiness in dogs somehow
itself has a systemic connection to cancer. I just read an article about psoriasis in humans correlating to a statistically significant higher risk of death by heart disease (300% higher!). The skin autoimmune disorder in humans has a heart connection, and it's believed to be related to inflammation. Maybe some skin disorders in dogs (which are poorly understood) have a systemic inflammatory component too, and maybe that unseen, internal inflammation could trigger some cancers under some conditions. All this is absolutely unknowable right now, but it makes me wonder if any data might point toward that possibility.
I'm not saying there's no connection between Apoquel and cancer. I'm just saying we don't know if there is -- but I hope more research is done. The connection could end up being like the "ice cream and polio" connection discussed in the first video I posted above....or not.