[Survival factors in 152 patients with gastrointestinal stromal tumors]

The gastrointestinal stromal tumor (GIST) is the designation for a specific type of mesenchymal tumor of the digestive tract that is origin in the interstitial cells of Cajal (ICC) or its precursor multipotentials, its presentation is rare and therefore its best knowledge must affect a proper diagnosis and treatment.

To evaluate the clinical characteristics and to identify factors influencing survival of patients with gastrointestinal stromal tumor.

This study design is quantitative, non experimental, descriptive, retrospective and transversal. The study has been performed in 152 patients with gastrointestinal stromal tumor who were treated at the National Institute of Neoplastic Diseases (INEN), Lima, Peru, from January 1999 through December 2009. For the final diagnosis was registered the outcome of the surgical and histology was complemented by immunohistochemical test. To assess the normal distribution of the population was used the Shapiro-Wolk, Anderson-Darling, Lilliefors, regarding the use of inferential statistical tables for survival and to assess its significance in the univariate analysis (p <0.05 significance), was used the Wilcoxon test, Tarone-Ware Log-rank and also to evaluate the difference between groups in contingency tables used the chi square and Fisher's test. Multivariate analysis was performed using the proportional hazards model of Cox.

The group of 152 patients included 78 women (51%) and 74 men (49%) with age range from 16 to 92 years, with an average age of 54. The frequency presentation was increased from the fourth decade of life and reaches its highest expression between 50 and 70. The initial presentation was with localized disease to 79 patients (52%) and primary metastases in 73 patients (48%), with an average time of disease 14 months. The prevalence of GIST tumor in the different organs was as follows: stomach with 77 patients (50.65%), jejunum with 21 patients (13.82%), retroperitoneum with 17 patients (11.18%), duodenum 11 patients (7.24%), colon 11 patients (7.24%), ileum 8 patients (5.26%),pancreas, 3 patients (1.97%), rectum, 3 patients (1.97%) and esophagus with 1 patient (0.66%). The most common symptoms of GIST tumors in general were gastrointestinal bleeding, abdominal tumor and abdominal pain. There are organ-specific symptoms such as jaundice in pancreas, dysphagia in esophagus and obstruction in the ileum. The tumor size greater than 10 centimeters was found in 92 patients (60.51%), 39 patients had size between 5 and 10 centimeters (25.65%) and 20 patients had lesions smaller than 5 centimeters (13.15%). Immunohistochemistry tests performed in 75 patients show that for all locations, the expression of KIT (CD117) is 94.8%, followed by CD34 to 70.35%; on the other hand, actin (61.68%) and S-100 (57.56%) have a smaller range of expression. Retroperitoneal GIST tumors had an expression of CD117 of 92.86% and CD34 of 60%, and GIST tumors of the pancreas had an expression of CD117 of 100% and CD34 of 100%. We evaluated 27 patients with low mitotic index, of which 10 had primary metastases (37%), in turn, of 25 patients with high mitotic index, 8 had primary metastases (32%). Of the 152 patients, 93 had complete resection of the disease, 28 had partial resection, 24 were unresectable and 07 did not undergo surgery, the more aggressive behavior was observed in ileum, 03 patients were unresectable, 02 patients had partial resection and only 02 could be completely resected, the rest of the series in general, for each location, the GIST tumors completely resected outscored the unresectable and partially resected. Of 93 patients that had completely resected, recurrence was found in 32 of these patients (34.4%), recurrence was local in 8 patients, metastases in 18 patients and local recurrence + metastases in 6 patients, with an average time of recurrence 22 months. The overall cumulative survival at 5 years was 81.35%. The survival of patients under and over 50 expressed a p = 0.08, cumulative survival rates by tumor size expressed p = 0.56, cumulative survival rates for stomach and intestinal location shows a p = 0.056. The 5-year survival of completely resected patients was 87.70%. Overall survival of patients with and without metastasis expressed p = 0.001, the cumulative survival function completely resected patients, the resected and partially resected, expresses with p <0.0001. Multivariate analysis showed that the most significant factor for disease progression was the primary metastases with p = 0.007, and that survival was directly related to complete resection of the disease which is expressed with p <0.0001.

The most important prognostic factor of survival for gastrointestinal stromal tumors (GIST) is the complete resection of the disease. The factor that is associated with progression of the disease is the presence of metastases. In our series of 152 patients, tumor locations tend to relate better survival in gastric GIST that in intestinal GIST. Similarly, we found a tendency to express a lower survival in patients younger than 50 years. Differentiated tumor size in three size categories expressed no more related to survival. The low mitotic index associated with metastasis, not reflected a good prognosis of disease.