Historically, limited trials evaluating biotherapy in treating metastatic neuroendocrine tumours have yielded mixed results. In this study, the efficacy of a novel combination therapy featuring long-acting Sandostatin LAR® plus α-interferon was evaluated. In a prospective case series, 12 patients with unresectable metastatic neuroendocrine tumours refractory to treatment initiated therapy with Infergen® and Sandostatin LAR®. Radiological response was followed serially at 3-month intervals. A biochemical response was considered significant if marker levels decreased by ≥50% compared with baseline. Inhibition of tumour growth lasting for greater than 3 months (mean response 22.6 ± 17.7 months) was seen in eight patients. Complete tumour regression was observed in one patient, lasting for 40 months; three patients exhibited partial tumour regression (mean response 29.3 ± 24.0 months), and four patients maintained a stable tumour response (mean response 13.3 ± 9.2 months). Four patients showed no response to therapy (mean response 5.0 ± 6.0 months). All enrolled patients are alive currently. The biochemical response seen in seven patients did not correlate with the radiological response. These results suggest that the novel combination of long-acting Sandostatin LAR® with an α-interferon may be at least as effective as either combination therapy with short-acting octreotide or monotherapy with Sandostatin LAR®.