You have to do what is right at the time
I don't know anything about chemo / bodily fluids but it sounds to me like you were advised to be super careful and that included using disps.
If you really want to (I know I would too) use cloth through the hard days perhaps buy something cheap which you can wash at 95 degrees just incase. Most nappies are not recommended to go that hot, but cotton terry squares would probably be the best option.
All of us, even 100% dedicated cloth users have some nappies sat in landfill (mine are from a couple of days in an incubator and then a 2 week holiday)