For some cancers yes, for other cancers, no. Sometimes resistance to therapy is a matter of time, not prior lines of therapy.

I wish I could find the article, but there is a clinic somewhere that ran trials where they deliberately wouldn’t treat the cancer too aggressively. Instead they experimented with treatment frequency but with control being the aim instead of elimination.

The theory being that they could keep it at bay indefinitely and lower the chance of selection pressure kicking in. The thought behind their approach is that they wanted their patients to die of something different than their cancer.