Combination therapy with octreotide and alpha-interferon: Effect on tumor growth in metastatic endocrine gastroenteropancreatic tumors

OBJECTIVE: We investigated the antiproliferative efficacy of the addition o f alpha-interferon to the somatostatin analogue octreotide in patients with metastasized gastroenteropancreatic tumors unresponsive to octreotide mono therapy. METHODS: In an open prospective trial, 21 patients with metastasized neuroe ndocrine gastroenteropancreatic tumors (nine patients with carcinoid syndro me, eight with nonfunctioning tumors, four with gastrinoma) were treated wi th 5 x 10(6) IU alpha-interferon tiw in addition to 200 mu g of octreotide tid. All patients, including 16 patients with preceding monotherapy with 20 0 mu g of octreotide tid, had tumor progression documented by computed tomo graphy before entering the study. Growth response (computed tomography docu mented) and biochemical response were assessed at 3-month intervals. RESULTS: Inhibition of tumor growth was observed in 14 patients (67%), 11 o f whom had preceding octreotide monotherapy; complete regression was observ ed in one patient lasting for 49 months and stable disease (stand-still) in 13 patients lasting for 3 to 52 months (median, 12 months). Seven patients failing this combination therapy exhibited a significantly shorter overall survival (median, 23 months; range, 5 to 42 months) than the 14 patients r esponding to this regimen (median, 68 months; range, 12 to 112 months; p = 0.007). Two patients are still alive. Biochemical response was achieved in 69% of patients with functioning tumors: in three of four patients with gas trinoma and in six of nine patients with carcinoid syndrome. CONCLUSIONS: These data suggest that the addition of alpha-interferon to oc treotide has antiproliferative efficacy in a subgroup of patients with adva nced metastatic disease unresponsive to octreotide monotherapy. Prolonged s urvival was seen in the responder group.