The only thing that has ever cleared up my cystic acne is low dose contraceptive pill (oestrogen and progestin combined). In talking to other acne sufferers I know, it seems like it's rather hit and miss as to whether people benefit.

I also use benzoyl peroxide most days to keep my non-cystic acne at bay.

If you've already went through a course of Accutane, there's a high chance that you've tried both of the above but that's what has helped me.