It's a fairly natural metric to choose if one wishes to gauge aspirin's effect on cancer risk, as the study's authors did.

Pardon me. Mentioning only curiosity was politeness. The more significant meanings I would supplement with are 'naive or suspicious'. By itself that metric really is worthless and reading this kind of health claim should set off warning bells. Lost purposes are a big problem when it comes to medicine. Partly because it is hard, mostly because there is more money in the area than nearly anywhere else.

Fortunately, the study's authors and I also interpreted the data by another standard. Daily aspirin reduced all-cause mortality, and didn't increase non-cancer deaths (except for "a transient increase in risk of vascular death in the aspirin groups during the first year after completion of the trials").

And this is the reason low dose asprin is part of my daily supplement regime (while statins are not).

"All cause mortality" is a magical phrase.