Taking your numbers at face value, it seems the problem you're having is the epidemiological interpretation of risk as it pertains to patient populations. You can decide for yourself if a 1/2600 risk is acceptable to you, but doctors are in a position to decide for a far larger number of people.
If 10m people are exposed per year to the given risk you outline, the expected number of additional cancers is ~4k people over 20y. In 10 years of scanning, that's 40k additional cancers over the next 30 years. For elderly people over 70, this may be less of an issue, but for everyone else, this is definitely a problem!
If 10m people are exposed per year to the given risk you outline, the expected number of additional cancers is ~4k people over 20y. In 10 years of scanning, that's 40k additional cancers over the next 30 years. For elderly people over 70, this may be less of an issue, but for everyone else, this is definitely a problem!