Roadrunner, Siti said that she and her husband had to fight just to get him treatment. They literally went halfway around the world for it. So that was the necessary part. He was then fortunate enough to respond to the chemo, which wasn't guaranteed. That's the "not sufficient" part in many cases, but at least it has been working for him for quite a while now. But not every patient is willing or _able_ to do the first part.
My husband did not respond to FOLFOX (they didn't use bev with it). I have a hypothesis for why he might respond to irenotecan (with bev probably required as an adjuvant) and radiation, but not folfox, which if correct makes me doubt that "maintenance chemo" with 5FU alone, even with bev, will be effective. But there's a chance that the small lymph-node mets have been killed, so we have two larger ones to contend with. He missed a cycle and his CEA shot back up at probably the same rate it had been increasing before he started chemo, and now we seem to be fighting something to a draw. I am anticipating the recommendation will be do some more rounds of folfiri, then 5fu-bev, and if those mets start to grow (which I regard as a near certainty) then maybe they'll consider doing something about them. I'd really prefer they be more proactive. Also, at least one met may require proton treatment since it's in a former radiation field. That's not available locally (although it wouldn't be too far to drive to get to a facility) but if you have additional mets they are likely to refuse it, even if those mets may be gone or manageable. "Not a candidate." We may be able to fib and say they are causing pain; they will often be more accommodating then.
Your signature indicates you were Stage III and they really do treat Stage IV patients differently. I suspect that many, like Siti's husband, are just written off immediately. We are fortunate that this hasn't happened to us yet. But overall the standard practice is not to try to get the patient to NED or at least close to it, but to "stable disease," which is usually a misnomer since most of the time it really means they've just slowed it down.
But you're quite right that individual circumstances have the most influence over outcome. What mutations do you have, what type of spread, etc. They just do not yet have a sufficient pharmaceutical arsenal to treat the different mutations and to prevent resistance from evolving. For a different example, my brother-in-law has serious cardiovascular disease despite a good diet and normal weight and regular exercising. That is also a lethal, incurable disease, but there are treatments and procedures and he can live decades longer. There is no such treatment for my husband, not yet. Some patients are lucky and respond to 5FU--before the other drugs like oxaliplatin and irenotecan were invented, it had pretty good success on its own overall. But many do not respond even to the best treatments available.
Also, it should not be a surprise that math and formal logic may share some terminology