Insulinomas, tumors of the insulin-secreting pancreatic cells, appear in middle-aged to older dogs and almost always metastasize. Treatment consists of surgical removal of visible lesions and includes dietary management and administration of drugs for hypoglycemia. The stage of tumor at diagnosis is the factor most closely correlated with survival time. Human unresectable or metastatic islet cell tumors, including insulinomas, have been responsive to streptozocin. Only a few cases of adjuvant use of streptozocin in dogs have been reported, and preclinical studies of toxic effects were shown to be dose-dependent.
In this study, a previously reported protocol for induction of diuresis during administration of cisplatin was adapted for use with streptozocin at a dosage of 500 mg/m2 IV every 3 weeks for dogs with metastatic insulinomas. Butorphanol was given IM as an antiemetic immediately afterward. Medical records of 17 dogs given this protocol were retrospectively reviewed and compared with those historical controls (15 dogs) treated traditionally with surgery, dietary management, and drugs for hypoglycemia. Only one dog treated with the streptozocin regimen developed azotemia. Serum alanine aminotransferase activity increased in some dogs but decreased when treatment was discontinued. Hematologic toxicosis was rare, and vomiting was uncommon but occasionally severe. Median duration of normoglycemia did not differ significantly between groups. Two dogs receiving streptozocin had rapid resolution of paraneoplastic peripheral neuropathy, and two others had measurable reductions in tumor size. Two dogs that developed diabetes mellitus after receiving five doses had the longest survival times.
COMMENTARY: This treatment can be safe and effective for metastatic insulinoma in dogs as long as renal function is supported via diuresis protocol during streptozocin administration.
Streptozocin for treatment of pancreatic islet cell tumors in dogs: 17 cases (1989-1999). Moore AS, Nelson RW, Henry CJ, et al. JAVMA 221:811-818, 2002.