Hi,
I don't have bladder cancer (my sister had it), but I have a small bladder capacity and wake up between 3 and 5 times a night from a dead sleep to pee. It's horrible. The only thing that helps is to stop with all fluid intake after dinner...otherwise...and still, I get up a couple of times.
I think the only way to get any rest is to make sure you get all that water in before say, 7PM? maybe 8?
Best of luck with things, and I hope things return to normal for you very soon.
Wendy