Autoimmune Reactions in a Patient with Malignant Insulinoma Treated by Multiple Low Dose Streptozotocin*)

Abstract
A 66-year-old female patient with a malignant insulinoma was treated with streptozotocin (STZ; Zanosar) in 5 cycles every 4 weeks as 5 day courses with an intravenous dosage of 850 mg per day. Under this treatment hypoglycemic episodes decreased continously in number as well as severity and — after a delay of 12 months after the last treatment — an overt diabetes mellitus appeared. Plasma insulin concentrations dropped immediately after starting of STZ therapy. On the other hand, islet cell surface antibodies and their complement-dependent cytotoxicity increased continously, being at their highest 6 months after termination of STZ treatment. Thus, STZ is able to induce a specific immune response against islet cells with a progressive damage of malignant insulin producing cells.