My dad had liver cancer which was detected early. We went with liver transplant and 3 months later, cancer reoccurred in lymph nodes in his lungs. Now, he's on

My dad had liver cancer which was detected early. We went with liver transplant and 3 months later, cancer reoccurred in lymph nodes in his lungs. Now, he's on immunosuppressants (tacrolimus and everolimus) for organ rejection. Can immunotherapy still be tried on him?