I previously received LTD benefits for mental health issues. Just after the 2 year mark the insurance company discontinued my benefits. (I was subsequently approved for CPP disability benefits). I then hired a lawyer to dispute the denial from LTD insurance company but it is just at the starting point with no resolution yet. About 2 months ago I was then diagnosed with cancer, have had surgery and will continue with chemotherapy and radiation. Should I be applying for new ltd benefits under this new illness even though I have remained off work the entire time? I am still technically employed and still have benefits (and thus I’m assuming I still have access to the same LTD benefits). Or is it impossible because I am suing the LTD insurance company for discontinuing my previous claim? thanks 
If you have a lawyer handling your disability case this is a discussion you need to have with them. Generally speaking, you can only start a “new” disability claim if you are “actively at work”. It is not enough to continue to be employed, you have to be actively at work and that is usually defined as a minimum number of hours per week in each insurance Policy.