We conducted a randomized , double-blind , placebo-controlled , multinational study of the somatostatin analogue lanreotide in patients with advanced , well-differentiated or moderately differentiated , nonfunctioning , somatostatin receptor-positive neuroendocrine tumors of grade 1 or 2 ( a tumor proliferation index [ on staining for the Ki-67 antigen ] of < 10 % ) and documented disease-progression status .