Incidence patterns of small bowel cancer in a population-based study in Sweden: increase in duodenal adenocarcinoma

Increasing incidences of malignant small bowel tumours have been reported, but data from European populations are limited. This study aimed to clarify the incidence patterns of malignant small bowel tumours in Sweden.

Patients with a first and primary malignant small bowel tumour were identified from the Swedish Cancer Register during the study period 1960-2009. Sex-specific and age-standardised incidence rates of these tumours were calculated by their anatomical location and histological type in different time periods. Figures were plotted to show the proportions and incidence rates over time, and joinpoint loglinear regression models were estimated to assess any time trends.

A total of 6604 patients with malignant small bowel tumours were identified. The age-standardised incidence of all malignant small bowel tumours increased from 14.2 to 19.7 per 1,000,000 person-years during the study period. The incidence of duodenal cancer increased more than 3-fold (from 1.6 to 5.4 per 1,000,000 person-years), which was mainly expained by a dramatical rising trend of adenocarcinoma of the duodenum (from 0.7 to 4.2 per 1,000,000 person-years). Malignant tumours of small bowel with unspecified anatomical locations showed a slight increase (from 7.0 to 7.9 per 1,000,000). The incidence of small bowel tumours in other locations or of other histological types was more stable.

The incidence of small bowel malignancies has increased during the period 1960-2009. Among the specific types of small bowel cancer, a particularly rapid increase was found for duodenal adenocarcinoma.