Hi Lis...my experience is that it took about a timeframe equal to the total rad/chemo treatment time before the effects of the treatments my Dad went through started to improve significantly. His treatments started beginning of April and went through almost end of May. By mid-July, started seeing some improvements, and by beginning of September, he was feeling well enough to get out and drive on short day-trips on his own.
So once that "low" following treatments was reached (about 4 weeks), he improved significantly week to week.
Alot of his improvement came with removal of the feed tube, as he felt more confident about being able to move around much more and that seemed to accelerate his improvement.
From a caregiver perspective, hope this helps a little.
Chuck