Prognostic analysis of patients with gastrointestinal stromal tumors: a single unit experience with surgical treatment of primary disease

Abstract

Background: Gastrointestinal stromal tumor (GIST), the most common type of mesenchymal tumors of the gastrointestinal tract, is a recently recognized tumor. The biological behavior of GIST is highly variable. Surgical resection remains the major treatment for GIST. In this study we retrospectively analyzed our surgical experience with 181 GIST patients to determine the effects of the treatment and the pathological features and prognosis factors of these GIST patients.

Methods: The clinicopathological features and follow-up data of the 181 patients with GIST who had received surgical resection between January 1999 and December 2007 at Ren Ji Hospital were retrospectively reviewed. Immunohistochemical stains including CD117 (KIT), CD34, and other markers were used. Tumor size, mitotic index and other pathological parameters were recorded. According to the consensus of NIH risk-group stratification system based on maximum tumor size and mitotic index (per 50 high power field), tumors were classified into very-low-risk group (15 tumors, 8.3%), low-risk group (48, 26.5%), intermediate-risk group (52, 28.7%) and high-risk group (66, 36.5%). Prognostic factors were analyzed by Cox analysis including age, sex, tumor size, tumor site, mitotic index, NIH categories and surgical procedures.

Results: One hundred and seven (59.1%) of the 181 tumors were located in the stomach, 51 (28.2%) in the small intestine, 9 (5.0%) in the colon and rectum, and 14 (7.7%) in other sites including the omentum and mesentery. The median age of the patients was 58 (range, 24-84) years, and 102 patients (56.4%) were male. Tumor size ranged from 0.5 to 30 cm, while the mean size was 7.02 cm. Metastasis was found in 7 patients. One hundred and seventy-six (97.2%) of the 181 patients underwent radical resection, and among them 26 patients received extensive resection with the adjacent organ adherent to the tumors. The positive rate for the KIT protein (CD117) in immunostaining was 94.5% (171/181), while that for CD34 was 86.2% (156/181). The 1-, 3-, and 5-year survival rates of the 181 patients were estimated to be 95.2%, 87.9% and 78.5%, respectively. There was a significant difference in age, tumor size, tumor site, mitotic index, NIH categories, and presence or absence of multivisceral resection (P<0.05). But there was no significant difference in sex between the groups. Cox hazard proportional model revealed that advanced clinical stage and large tumor size contributed to worse prognosis. The patients who were treated with imatinib because of recurrence and metastasis or high recurrence risk showed stable disease.

Conclusions: Surgical resection is the gold standard of treatment for primary GIST. NIH categorization is simple and effective to evaluate GIST behavior and prognosis. Targeted therapy such as imatinib, a KIT tyrosine kinase inhibitor, may play an important role in the treatment of GIST.