The aim of this study is to compare the efficacy and safety of lanreotide Autogel and Sandostatin LAR Depot, to see whether these two 28-day prolonged release formulations produce a similar clinical response in patients with carcinoid syndrome.

Inclusion Criteria:

• Histologically confirmed diagnosis of a neuroendocrine tumor of the carcinoid type.
• Documented evidence of carcinoid syndrome (flushing and/or diarrhea) attributable to a primary tumor of the lung, stomach or mid-gut.
• Previous positive Octreoscan.
• World Health Organization (WHO) performance score lower than 2.

At the baseline visit patients MUST satisfy the following criteria before they are randomized to receive study treatment:

• Stool and/or flushing frequency of greater than or equal to 3 episodes/day (average over a minimum five consecutive days).
• Patients who have previously been treated with somatostatin analogues must have discontinued treatment for a sufficient period of time (a washout period of at least 7 days for immediate release formulations and up to 2 months for prolonged release formulations is usually required). Compared with their "controlled" state on treatment, these patients must show a clinically significant deterioration (at least two episodes) of either symptom. For example, a patient considered to be controlled on their previous treatment with an estimated stool frequency of two episodes per day, must achieve a stool frequency of at least four episodes per day (average over a minimum five consecutive days).
• WHO performance score lower than 2.

Exclusion Criteria:

• VIPoma or other non-carcinoid tumor.
• Treatment with interferon, chemotherapy or radiotherapy given within 30 days prior to inclusion, or planned during the study.
• Radionuclide treatment within three months prior to inclusion, or planned during the study.
• Presence of other active malignant pathology (except basal cellular carcinoma of the skin and/or in situ carcinoma of the cervix/uterus).
• Surgical procedure or embolization procedure (with or without cytotoxic agents) of the tumor within three months prior to inclusion, or planned during the study.
• Life expectancy of less than 6 months.
• Any investigational drug given within 30 days prior to inclusion or expected to be given during the study.
• No access to a telephone for completion of the daily telephone diary.