You are just assuming that all cancer must be treated if detected, even if it is medically unnecessary, therefore we must not detect medically insignificant cancer which would be net harmful to treat. You can detect things and determine no action should be taken. I can understand if that might be the modern standard of care, but if so then that is the problem; not early detection of cancer, which could be medically insignificant, but which may also allow the early detection of medically significant cancer.