Last night at supper, a family member mentioned a person he follows on Twitter. That man has been a proponent of aspirin for preventing cancer and bemoans the slow pace of the medical world to agree. I looked him up on the web - he mentions having degrees in biology and microbiology, but is not practicing in that field.
I dug around on a few sites after supper, and found little. I tried Forbes, thinking they would be likely to give references to well-controlled studies. And of course, I am interested mainly in breast cancer. Their 2013 article led me to the Scottish study mentioned below, and also mentioned 2012 studies from The Lancet. Excitement, but not many specifics.
A Scottish study was mentioned in two articles indicating results that aspirin helped to prevent breast cancer. However, one article also mentioned that an American study got the opposite results.
Much reportage I found seemed to have inconsistencies that were not backed up by specific study results. In one report, aspirin was discussed as a help with colorectal cancer. Another article specifically stated that most good results for aspirin with colon cancer seemed to occur in the rising and transverse colon - the opposite side of the colon.
Almost every study report mentioned the ongoing danger of internal bleeding. Cancer Research UK was not helpful, no statistics in their aspirin-nsaid (ibuprofen,etc) mention. They did say you must not take aspirin for prevention if you have ever had an ulcer.
If I do more research, I'm going to stick with my tried and true formula:
Remember we have known for decades that aspirin can cause stomach bleeding.
Ignore opinions that say "studies show." Get the study name and the qualifications of the researchers, and any info on the study design for accuracy. And who paid for it!
Pay more attention to established top medical journals than to popular articles (even mine).
Get a second opinion. Maybe a third. Doctors are not always right. Not even on tv. Especially on tv.
Don't base decisions on reports given at conferences. Find out what gets printed in a peer-reviewed medical journal.