Prognosis of gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors (GIMT) of the gut. The aim of this retrospective study is to correlate the histological risk factors with the survival of our patients operated for GIST.

In our department, from 1980 to October 2003, 15 patients were operated for GIST. Their mean age was 58 years old and 8 of them were males; 10 (67%) were localized in the stomach and 5 (33%) in the small bowel. In 7 cases liver metastases were present at laparotomy and 4 of them also had peritoneal diffusion. We performed immunohistochemistry for c-Kit, SMA and S100p. Mitotic index (MI) and size neoplasm were the main pathological criteria for malignity. The patients with c-kit (CD117) positive neoplasms were divided according to NIH Consensus Conference risk class, MI, tumor size, localization, SMA or S100p presence, liver metastasis and peritoneal metastasis to compare the different 5-year survival rates. Survival analysis was performed using Kaplan-Meier method and log-rank test and a p < 0.05 was considered as significant.

Global survival rate after 5 years was 40% and the mortality was, in all cases, due to GIST. In our experience gender, age, tumor size, localization and S100p positivity did not play any role in predicting the prognosis of GIST. On the contrary high MI and SMA positivity are significantly associated to a lower survival rate (33% vs. 86% and 39% vs. 100% at 5 years, respectively). Finally patients with metastases at laparotomy have a significantly lower 5-year survival rate (hepatic 29% vs. 100%, hepatic and peritoneal 25% us. 78%).

In our experience high MI and in some cases SMA expression can be considered assessed risk factors. On the other hand, criteria of benign behavior did not completely predict the long-term clinical outcome.