There's also a lot of confusion due to reported survival rates which are basically always higher if you screen but that does not mean people live any longer (or happier).
Even if you could, it does not help if there isn't a good treatment.
That's why screening for some cancers (e.g. breast and prostate) is controversial.
First of all you might get false positives or negatives. False positives can harm patients since they get worried and might even get treatment for a disease they don't have.
Secondly even if the screening gives a valid result: In some cases (like mentioned before PC and BC) that does not mean the patients live any longer than the ones who where not screened.
There's a 5-year survival time metric which makes screening look very positive.
Let's say you and a friend have a cancer that will kill you in 10 years, no matter what. If you get screened after 4 years, you'll have a 100% 5-year surivival rate (so screening is celebrated as a success: more screening!).
However, you won't live a second longer than your friend. You will be worried though and might get treatment with serious side effects.
That's why the mortality rate is IMO an actually much more interesting metric.
https://www.youtube.com/watch?v=gNiORew3uRY