BACKGROUND: Gastrointestinal stromal tumors (GISTs) have been recognized as the most common mesenchymal tumors of the gastrointestinal tract. The most effective treatment for unresectable tumors is imatinib mesylate, based on two phase II trials. Because no phase III clinical trial has been undertaken, we sought to determine both current population-based incidence and whether improved outcomes noted in both individual centers and clinical trials have also been observed in a large prospective cancer registry earlier and after the introduction of imatinib. STUDY DESIGN: The 13-center cumulative tumor registry (April 2005 release) from the Surveillance, Epidemiology, and End Results (SEER) database was queried from 1992 to 2002 to determine incidence and associated outcomes for patients diagnosed with GIST. Confirmations of incidence trends using the incident Florida Cancer Data System (FCDS, 2005 release) were also determined. RESULTS: A 25-fold age-adjusted increase in incidence of GIST, from 0.028 per 100,000 in 1992 to 0.688 per 100,000 in 2002, was observed. This increase is mostly because smooth-muscle tumors have been reclassified as GISTs, but it also represents a 50% increase in population- and age-adjusted gastrointestinal mesenchymal tumor diagnosis since 1992. Despite rising GIST incidence rates, there has been a marked improvement in survival since 2000, coinciding with the introduction of the tyrosine kinase inhibitor imatinib into clinical practice. CONCLUSIONS: The diagnosis of GIST has dramatically increased since 1992. Survivals have greatly improved since 2000, when imatinib mesylate was FDA approved.
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