4232 Background: The definition of gastrointestinal stromal tumors (GIST) has evolved over time and its true incidence is still unknown, probably underestimated. We have reviewed 161 cases of soft tissue tumors of the GI diagnosed in the province of Modena between 1988 and 2002 and registered in the Modena Cancer Registry, with the aim of establish the true incidence and the clinical behavior of the disease.
METHODS
Diagnostic samples were investigated by ICC for CD117 (Dako), PDGFR-A (Santa Cruz) actin, desmin, S100, and CD34. Cases were classified as GIST if resulted KIT+/PDGFR-A- or KIT-/PDGFR-A+.The tumor behavior was assessed on the basis of tumor size and mitotic count, according to the Consensus panel.
RESULTS
The diagnosis of GIST was confirmed in 113 cases, 98 KIT+ (87%) and 15 KIT- (13%). The incidence of GIST was of 13 cases per million inhabitants/year. The GIST identified in our population represent 1,1% of all GI cancers diagnosed in the last 15 years. Fifty seven (50%) were men and 56 (50%) women. Median age at diagnosis was 67 years. Sixty four tumors (57%) arose in the stomach. The risk of aggressive behavior was very low, low, intermediate or high in 13%, 12%, 19%, and 55% of cases, respectively. The most frequent symptoms were abdominal pain (37%) and GI bleeding (21%). Twenty one patients (19%) were asymptomatic. Eighty-six patients (76%) underwent radical surgery. After a median follow-up of 46 months (68 months for pts alive) the 5-year survival rate was 53%. At the same interval the survival rate was 75%, 70% and 72% for patients at very low, low and intermediate risk, and 42% for those at high risk (P = 0.0065). The 5-year relapse-free survival rate after radical surgery of primary GIST was 94% for patients at very low, low and intermediate risk, and 43% for patients at high risk (P < 0.0001).
CONCLUSIONS
GIST represent a rare but well recognizable disease. The risk of aggressive behavior is high in more than 50% of cases. The finding that after radical surgery all relapses but two occurred in patients classified at high risk of aggressive behavior, confirms the clinical usefulness of the Consensus approach. No significant financial relationships to disclose.