Temporal trends of incidence and survival of sarcoma of digestive tract including Gastrointestinal Stromal Tumours (GIST) in two areas of the north-east of Spain in the period 1981-2005: a population-based study.

INTRODUCTION: The diagnostic approach of Gastrointestinal Stromal Tumours (GIST) was established in 2002. Before this, GIST had been classified with a wide range of histological terms. This fact and the consideration of potential malignity of all these tumours led to a false perception of an increasing incidence.
PURPOSE: This study aimed at evaluating the accuracy in registration of sarcoma of digestive tract and GIST and to elucidate the trends of incidence and survival of those.
MATERIALS AND METHODS: We used data from two population-based cancer registries in Spain. In the Girona's Cancer Registry we previously reclassified all sarcoma of digestive tract performing c-kit to confirm GIST and analysed the time period 1994-2005. In Tarragona's Cancer Registry, where we analysed the time period 1981-2005, this reclassification was not done.
RESULTS: We obtained a significant increasing trend in incidence of all sarcoma of digestive tract in the Tarragona Cancer Registry database, with an annual per cent of change of 3.87 but a non-statistically significant trend in incidence in the Girona Cancer Registry database. The incidence of GIST in Girona Cancer Registry was 1.24 cases/100,000 inhabitants/year. Survival rates did not change in time and was high in less aggressive GIST. The 5-year relative survival for low, intermediate and high risk of malignant behaviour GIST groups were, respectively, 80.5, 85.6 and 64.6 %.
CONCLUSIONS: The increase in the incidence of GIST could be explained by the improvement in their diagnosis and registration. The survival of low and intermediate risk of malignant behaviour is high and close to normal population survival.