Long-term treatment of metastatic medullary thyroid carcinoma with the somatostatin analogue octreotide.

Three patients with symptomatic metastatic medullary thyroid carcinoma (MTC), one with sporadic form and two with MEN IIa, were treated with the long-acting somatostatin analogue octreotide (SMS 201-995, Sandoz) for 3 to 17 months. Octreotide was administered subcutaneously in a starting dose of 0.6 to 1.0 mg/day by automatic pump (Travax ASH6, Travenol). Symptoms of diarrhoea, weight loss and malaise improved in all patients. Maximal percentage decrease in mean serum calcitonin was 47, 52 and 81% of the basal values, and was observed 1-3 months from the beginning of treatment. Likewise, carcinoembryonic antigen (CEA) levels initially dropped to 45, 60 and 63% of the levels before therapy. A continuing effect was seen in the two patients with MEN IIa after 15 and 17 months of treatment. However, after the initial decrease, calcitonin (CT) levels went up again to 67 and 68% of the basal values and the dose of octreotide had to be increased to 1.5 mg and 2.0 mg/day. CEA also returned to 84 and 105% of the pretreatment titres. Response to 1.5 mg/day octreotide was lost in the patient with the sporadic form of disease after 3 months. Side-effects were minimal. Effects on tumour size could not be evaluated. These suggest that octreotide might be a valuable adjuvant in the long-term management of metastatic MTC. Tachyphylaxis may occur.