I lost my wife to melanoma that metastasized to her brain after cancerous mole and margin was removed 4 years earlier. They did due diligence and by all signs there was no evidence of recurrence, until there was. They think that the tumor appeared 2-3 months before symptoms (headaches) appeared, so it was unlikely that you’d discover it otherwise.
With something like this, maybe you could get lower dose immunotherapy that would help your body eradicate the cancer?
Literally anything that reduces cancer deaths is a win. I'm certainly not campaigning against early detection tests like this! Just talking about a challenge that comes up operationalizing them.