In order to go on disabilty you usually need your doctor to state you are unable to work and your employer, these are they requirements for private insurers, such as your group disabilty, and privately owned disability in the USA. As far as govenment disabily you have to be off work for 6 months and they automatically decline the first request and you need to reapply with an attorney. you may want to check with your employer to find out the waiting period before they will pay the benefit.
I also was on lupron( I had one 3 month injection and never had another) and found the side effects very nasty to live with. Today I treat my cancer with holistic treatment and it has been successful for 3 years.
If you could convince your doctor to go along with it you have a good chance to collect from the insurance company.
hope this helps
Dan