Hi Pamela,
First off, thoughts and hugs. It's never easy to be going through a serious medical challenge, and all of the paperwork that accompanies it doesn't help.
It is important to stay on top of that paperwork, as you know. Here is what I suggest:
For all paperwork related to this particular health challenge, I would suggest a you keep a portable file box for all of it...which it sounds like you're already doing.
Nothing else should go into this file box. It can include a folder for your oncologist bills, hospital bills, cancer information that you're following, current medication, insurance statements and bills, etc. This way, it's all in one place and you know where to go when you need any of it.
For all other long-term paperwork, a filing system is a must. For most people, I suggest a small filing cabinet. But you can get away with file boxes if you need to depending on your space and budget.
There are tons of categories that I have already been thought-out for you (including those you mentioned) and you can add your own as well.
For your short-term paperwork, which is essentially paperwork that's in process right now, a file box (like your tabletop file box) or a 3-ring binder with 3-hole punched pocket folders would be perfect for this purpose.
Think of this as your "Action Box."
You can either have categorized folders in there, such as "To Read," "Keep for 30 Days," or "Project A," etc. (Actually name your projects, though.)
Or, you can set it up as a Tickler File System with a folder for each day of the month, numbered 1, 2, 3, 4, etc. all the way to 31.
For papers you need to deal with on the 6th of the month, they go in the number 6 folder. For papers you're going to work on, on the 21st of the month, they go in the 21 folder. And so on.
Note: You have to be very good about checking this numbered system every single day, otherwise it's not going to work. Set your phone alarm to sound each morning and check the folder for whatever day it is.
Finally, you mentioned you have to keep track of appointments. As soon as you have an appointment, jot it into your paper calendar or type it into your phone calendar.
I hope some of these ideas help! Take care and please stay in touch.