In theory it’s possible the best early treatment is no treatment at all; that there might be such a thing as too-early detection.
For example, a PSA test is useful to detect cancer of the prostate, if a male patient has urination problems. But doing general screening for high PSA values in middle aged men is not considered a good idea, because there are too many false positives and it would likely lead to many unnecessary invasive interventions.
Two people develop a fatal cancer at T0. One is diagnosed at T1, the other at T2, both die at T3.
It looks like the first person survived longer with cancer than the second, but they didn't: the interventions had no effect, it's just a statistical artifact.
This is by no means always the case - earlier detected cancer is more treatable - but it still needs to be controlled for.