I can't understand why you are still in the reserves!
In my 20 years of Navy service I NEVER heard of anyone with cancer who staying in the service - NEVER - and I new at least a dozen people who had cancer or other major illnesses who were discharged with some type of disability. Did you perhaps keep your cancer to yourself?
Perhaps you didn't persue all avenues available to you. Or perhaps you didn't really have cancer and are just bitching.
I tend to think that you are not being truthful in your letter. So I'm sorry to throw water on your fire, but the facts just don't add up.
I would say your 20 years was spent oblivious to exactly how the branches dealt with servicemembers that have/had cancer. I tell no lies, use your imagination and realize that everything you know is not everything.