Antiproliferative treatment of patients with metastatic endocrine gastroenteropancreatic tumours (GEP) is based mainly on chemotherapeutic protocols whereby drug toxicity is a major handicap. Octreotide is the first choice in the control of hormone mediated symptoms.

A prospective study was performed to determine the efficacy of octreotide (Sandostatin; SMS 201-995) 200 micrograms tid in controlling tumor growth. The study included 21 patients with metastasized endocrine GEP tumors: 6 gastrinomas, 8 carcinoid syndromes, 7 nonfunctioning tumors. Treatment was performed for 3 to 59 months (median 15 months). Evaluation of the response to octreotide was facilitated in 12 patients by a pretreatment observation period of 3 to 47 months (median 17 months) during which the natural growth behavior was determined. Based on the presence or absence of a control period prior to treatment, 5 patients were considered to be responders, 7 as questionable responders (no pretreatment phase available), and 9 as nonresponders. None of the 21 patients had documented shrinkage of the tumor mass. The most favorable response was tumor standstill. In all but one responder an escape to an initially favorable response occurred after 6 to 28 months (median 14 months). Proved inhibition of growth was paralleled by a reduction of serum and urine hormone parameters, whereas unaltered progression of tumor growth was observed also in the presence of hormone suppression. Tumor growth and hormone release was inhibited in the absence and presence of somatostatin receptors on the tumor. It is concluded that octreotide exerts a limited effect on metastatic GEP tumor growth. The evaluation of a response to octreotide is facilitated by an observation period prior to the drug that provides information on growth characteristics of the tumor. The presence of octreotide receptors does not predict the success of therapy.

One hundred and fifteen gastroenteropancreatic (GEP) patients with malignant endocrine tumours entered a prospective multicentre trial (12 patients with gastrinoma, 53 with carcinoid syndrome, 45 with nonfunctioning tumours and 5 with other endocrine GEP tumours) to determine the efficacy of 200 μg Sandostatin® t.i.d. in the control of tumour growth. This interim report describes the results in 85 patients. Thirty-four patients died, 14 before and 20 after the first follow-up investigation, indicating a ‘negative’ selection of patients included in the trial and suggesting that Sandostatin® is unable to prevent disease progression when it is far advanced. In the evaluation of 68 patients followed up for at least 3 months, partial regression was observed in 4.4%, stable disease in 50% and tumour progression in 45%. An initially favourable response occurred frequently, however, it was followed by a decrease in response, from 54.4% at 3 months to 38% at 12 months, for the whole group of patients. Proven inhibition of tumour growth was mirrored by suppression of serum and urine hormone parameters. It is concluded that Sandostatin exerts a beneficial effect on tumour growth in patients with metastatic endocrine GEP tumours. This beneficial effect decreases with time and is as yet unpredictable in the individual patient.

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