cancer survivor and fitness I am a two-time cancer survivor ...head/neck and lung (they removed a lobe in the second instance) ... I have been biking for a couple of years now (I bought a fixie, since it was cheap and I wasn't sure I would be able to cut it), and I try to ride three or four times a week, but in the range of 5-8 miles each session.  I like to think this is helpful in terms of overall fitness and breathing, but haven't found anything to confirm this. Always trying to expand on distance, but so far stuck in this range.
 Thoughts?
A perfectly reasonable question.

Cycling is gererally thought of as being an excellent way of keeping fit. It is seen as beneficial for cardio- health and for leg muscles (not so much for arms), and is low-impact on joints. On top of that I would add that the benefits are proportional to the amount of effort you put into it.

Of course, how safe this exercise is for the individual would depend on the individual themselves, their existing fitness etc. and any pre-existing medical conditions. An individual should discuss any proposed fitness regime with their doctor. So where your question becomes impossible to answer is how reasonable your fitness regime is for you, and any improvements you could make. But that holds true across the board.