Prof Peter Rothwell, from Oxford University, and colleagues, who carried out the latest work, had already linked aspirin with a lower risk of certain cancers, particularly bowel cancer.
But their previous work suggested people needed to take the drug for about 10 years to get any protection.
Now the same experts believe the protective effect occurs much sooner - within three to five years - based on a new analysis of data from 51 trials involving more than 77,000 patients.
And aspirin appears not only to reduce the risk of developing many different cancers in the first place, but may also stop cancers spreading around the body.
Taking a low (75-300mg) daily dose of the drug appeared to cut the total number of cancer cases by about a quarter after only three years - there were nine cancer cases per 1,000 each year in the aspirin-taking group, compared with 12 per 1,000 for those taking dummy pills.
It also reduced the risk of a cancer death by 15% within five years (and sooner if the dose was higher than 300mg)
And if patients stayed on aspirin for longer, their cancer death risk went down even further - by 37% after five years.
Low-dose aspirin also appeared to reduce the likelihood that cancers, particularly bowel, would spread (metastasise) to other parts of the body, and by as much as half in some instances.
Oh yeah, the "you're welcome" part? You see, a distant relative of mine, let's call him 43rd cousin Heinrich, led the team at AG Bayer that developed what we know today as aspirin. Heinrich went on to develop yet another miracle drug - heroin. He thought it would have all the heroic qualities of a first-rate opioid but without being addictive. Oopsie! Forget about that part and take your aspirin, dammit.