The present invention is directed to a method of decreasing the rate of proliferation of medullary thyroid carcinoma cells which comprises contacting medullary thyroid carcinoma cells with one or more SSTR2 agonist. A somatostatin receptor antagonist having the formula Cpa-cyclo(D-Cys-4-Pal-D-Trp-Lys-Thr-Cys)-Nal-NH2 is also disclosed.