Have the doctors achieved the maximum tolerated dose of mitotane for your boyfriend?
Was he suggested radiotherapy?
Usually, clinical benefits (reduction in tumor mass, reduction in pain, weakness or anorexia and reduction of symptoms and signs due to excessive steroid production) are observed after 3 months at the maximum tolerated dose and if there are no benefits, it is considered a clinical failure.
Usage of metyrapone and ketoconazole for the correction of hypercortisolemia in Cushing’s syndrome is well established and they are often used preoperatively (mitotane is indicated in the treatment of inoperable adrenal cortical carcinoma, so, I guess that's why he wasn't suggested metyrapone and ketoconazole) Sorry, if I'm making unbiased conclusions.
Best wishes for you and your boyfriend!
Marija