Clinical and immunohistochemical studies of small bowel carcinoid tumours

Abstract: Small bowel carcinoid tumours arising from enterochromaffin cells in the jejunum and ileum are neuroendocrine tumours (NETs) characterized by secretion of serotonin, tachykinins and other bioactive substances. These substances may lead to the typical carcinoid syndrome as well as pronounced fibrosis locally and in the heart. Although the most frequent histological subtype of malignancy in the small bowel, small bowel carcinoids are rare and therefore difficult to study. We found that previous studies either described selected patients at referral centres, or were based on limited data from large registries. The main objective of this thesis was to investigate small bowel carcinoid patients from a geographically defined cohort with no selection bias.PAPERS I AND IIThe aims of papers I and II were to investigate the incidence, histopathological characteristics, stage atdiagnosis, symptomatology, surgical treatment, prognostic factors and survival of small bowel carcinoid.All patients resident in Jönköping County when diagnosed with small bowel carcinoid between 1960 and2005 were eligible for inclusion. After thorough review of medical records and reexamination of availabletumour specimens, 145 patients were included.A higher incidence of small bowel carcinoid than previously described was found: 1.12 per 100,000 persons and year. The incidence increased during the study period. Symptoms were most often uncharacteristic: the carcinoid syndrome was seen in only 13% of symptomatic patients. Many small bowel carcinoid tumours presented as surgical emergencies without preceding symptoms, often as intestinal obstruction (35%) caused by mesenteric fibrosis. The majority of small bowel carcinoid tumours had metastasized to the mesentery or the liver at diagnosis. Disease-specific survival after 5 years was 75.0% and after 10 years 63.5%. Independent prognostic factors for worse disease-specific survival were higher age at diagnosis, more advanced disease stage at diagnosis and incomplete tumour resection. Completeness of resection was of particular importance in patients with regional metastases.PAPER IIIThere are previous case reports describing small bowel carcinoid in two first-degree relatives, but it is unknown whether this represents hereditary disease forms or chance. Paper III was the first article to describe metastasizing ileal carcinoid tumours in three consecutive generations ? strongly suggestive of a hereditary disease form.PAPER IVWe recently demonstrated expression of cocaine- and amphetamine-regulated transcript (CART) in several types of NETs, including small bowel carcinoid. The aim of paper IV was to investigate whether content of CART in small bowel carcinoid tumours is associated with tumour characteristics, symptoms and survival. CART expression was examined in all available tumour specimens from the patients in Papers I and II ? 97 patients were included.Presence of CART IR tumour cells was associated with histological grade, but not with stage or age. CART expression in small bowel carcinoid tumours was not associated with clinical symptoms. Increasing levels of CART IR in small bowel carcinoid tumour cells was associated with worse disease-specific survival. CART was also found to increase cell viability in an enteroendocrine cell line in vitro. The results suggest that CART could be used as a prognostic biomarker and that CART is a potential anti-tumour treatment target.