Epidemiology of small intestine cancer in Iran

BACKGROUND: Little is known about the epidemiology of small intestine (SI) cancer in Iran, a rare cancer entity worldwide. AIMS: The aim of the present study was to investigate the incidence patterns and survival rates of SI cancer in Iran through a population‐based study. METHODS AND RESULTS: Data on all reported cases of SI cancer were extracted from the Iran National Cancer Registry based on ICD‐O‐3 codes. Age‐standardized incidence rates (ASIR), age‐specific incidence rates, standardized rate ratios (SRR), time trends, and absolute survival rates were calculated. During 2005–2015, a total of 4928 SI cancers (ASIR: 0.87/100 000) were diagnosed, including 2835 carcinomas (ASIR: 0.51), 214 neuroendocrine malignancies (ASIR: 0.04), 228 sarcomas (ASIR: 0.04), and 704 lymphomas (ASIR: 0.11). Carcinomas and lymphomas occurred more frequently in men than in women (SRR: 1.37/100 000 and 1.85/100 000, respectively), while the other two histological subtypes were almost equally distributed. 78% of carcinomas and 53% of neuroendocrine tumors were located in the duodenum. Sarcomas occurred most frequently in the jejunum (41%), while lymphomas were most frequently in the ileum (44%). From 2005 to 2015, the number of reported cases of SI cancer increased by 9.6% per year. The median age of diagnosis for women and men was 61. The absolute 5‐year survival rate was 35.3%, varying by sex, age, and subtype. Carcinomas had the lowest survival rate (24.1%) while neuroendocrine carcinomas had the highest survival rate (69.7%). CONCLUSION: Epidemiological patterns of SI cancer in Iran differed slightly from patterns in the United States and the United Kingdom. In contrast to other countries, the neuroendocrine form is presented as the rarest subtype in Iran. The overall incidence of SI cancer was lower in Iran than in high‐income countries. In contrast, the average prognosis of SI cancer was worse in Iran, indicating the need to improve early detection, diagnosis, and treatment.