There's a lot about biology that makes cancer fundamentally hard to treat, and the efficacy of cancer treatments fundamentally hard to measure. I'm optimistic that we'll eventually get to a point where we can meaningfully say we "cured cancer", but it will almost certainly be a cluster of thousands of treatment protocols which each have to be tested over 5-10 years for recurrence. There's no reason to expect that there should exist any broad-spectrum cancer treatment better than radiotherapy, or any fast test to determine whether long-term remission will be achieved.