I had stage 4 colon cancer (mets to liver). When I was going through chemo, I made sure to work out the morning of an infusion day.

I recall seeing some articles that exercising can sometimes help make chemo more effective and help prevent muscle atrophy that can sometimes occur. I believe it helped me.

I often tell people that CrossFit and chemotherapy saved my life because I did not seek out or undergo any non-conventional treatments or therapies. Now, I had been working out and was in great shape before starting to decline and, ultimately, being diagnosed, so that starting state certainly helped me endure things as well. It was also wonderful to just be in the moment and focused on exercise for a little while instead of constantly thinking about cancer, so it was also a nice mental break in addition to any physical benefits. My friends at the gym were also phenomenal in terms of support, both moral and real world, e.g. meal trains, financially and any other way you can think of. It would have been a lot more difficult without their support.

Anyway, I know this is an old thread, but I just joined the site and thought I'd share my experience with this topic. Best wishes to those still going through it. Do what you can when you can, but never feel bad if it's all too much for you at times.