Aspirin may increase rates of some cancers.

https://discover.dc.nihr.ac.uk/content/signal-000696/aspirin...

> In the ASPREE trial, older adults with no apparent cardiovascular disease who took daily aspirin saw no benefit in terms of reducing the chance of dying or having dementia or disability. Instead, it slightly increased their mortality and bleeding risk - aspirin was associated with an excess of 1.6 deaths per 1,000 people per year. Half of these deaths were due to cancer.

(Although this is at odds with other research and so we need to be careful when interpreting it).