[gjulianm]

> If the test detects cancer that doesn't need treatment, don't treat it!!

How do you know which ones to treat and which ones to leave?

[IshKebab]

When the result is above a chosen threshold (which may depend on other factors like family history etc.).

[gjulianm]

Unfortunately that "chosen threshold" is really hard to know, specially if you want to balance individual and population level necessities.