I was doing chemo for colon cancer when I started back in 2004. I had read a study that showed a strong negative correlation between exercise and the return of cancer, so I decided to get back into cycling. My first ride was three miles, and when I got back I spent 45 minutes on the bed panting, trying to catch my breath. A few days later blood work showed that the chemo had crashed my red blood count, and I got a couple of shots of Aranesp, a form of EPO. Believe you me, EPO is magic juice. My blood count jumped, and I felt much better.
The cancer came back in 2005, and I started back a second time in 2006 during my third, and last, session of chemo. In looking back at my records from that time, I note a ride of 17 miles (a route that has become a standard ride) that took 1:16:12, a speed of 13.4 mph. Less than a year later my PR was 52:19 over the same route.
There are two eternal truths about cycling: You can always get better, and there is always someone better than you.