Effect of streptozotocin in a case of glucagon-secreting malignant islets-cell tumor.

A case of a 65-year-old woman with a pancreatic tumor secreting insulin, glucagon, and associated with high PTH levels and hypercalcemia is reported. The patient underwent two Streptozotocin (STZ) treatments (1 g iv/week for 10 weeks) after liver metastases were found. Hormonal and metabolic parameters were monitorized . Before the first STZ treatment insulin levels ranged between 78 and 132 microU/ml. After STZ administration insulin decreased and then remained lower (8-48 microU/ml) until the death of the patient. Pre-treatment glucagon levels ranged between 1.3 and 3.9 ng/ml. STZ induced a decrease of glucagon to 0.5 ng/ml. Glucagon chromatography revealed the prevalence of high molecular weight (greater than 6,000 mol wt) immunoreactive glucagon (0.9 ng/ml) drastically reduced by STZ treatment (0.15 ng/ml). Hypoaminoacidemia was observed before STZ administration, but at the end of the therapy plasma amino acid concentrations were normal. Hypercalcemia too was sensitive to STZ, but not PTH value, which remained high. The second STZ treatment performed a year later was less effective and so a chemotherapeutic protocol was started. Our findings suggest a cytolitic effect of STZ on malignant A-cell, with reduction of glucagon levels and restoration of amino acid metabolism. This effect would be useful for medical treatment of non-operable glucagon secreting tumors.