Prognostic factors for primary gastrointestinal stromal tumours: are they the same in the multidisciplinary treatment era?

Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumour of the gastrointestinal tract. The introduction of tyrosine kinase inhibitors (TKIs) has lead to increasing use of combination of medical and surgical therapy. The aim of this study was to look at outcomes from a series of surgically treated GISTs and determine prognostic factors in the context of multimodal therapy. We analysed 104 single surgeon's patients with GIST. End points of the study were disease-specific survival (DSS), disease-free survival (DFS) and post-operative complications. Three- and 5-year DSS rates were 96.7 and 94.6 %. On univariate analysis, clear resection margins were predictive of DSS. Patients with R2 resection had a worse prognosis (3-year DSS rate of 83.3 %; 5-year DSS rate of 62.5 %) compared to patients with R0 (3-year DSS rate of 98 %; 5-year DSS rate of 98 %) or R1 resection (3-year DSS rate of 100 %; 5-year DSS rate of 100 %) (R0 vs R1 vs. R2 p = 0.001). Pre-operative factors associated with R2 resection were clinical metastatic disease (p < 0.001), non-gastric tumour site (p = 0.002) and large tumour diameter (p = 0.031). Three- and 5-year DFS rates were 65.5 and 59.8 %. Serosal perforation (p = 0.013) and mitotic rate (p = 0.05) were found to be independently predictive of increased DFS. The presence of serosal perforation was associated with tumour site (p = 0.018), mitotic rate (p = 0.035), tumour diameter (p < 0.001), growth pattern (p = 0.007) and age (p = 0.040). In the multidisciplinary management of GIST, serosal perforation may represent an additional predictor of recurrence along with mitotic rate. Complete macroscopic surgical resection is the most reliable prognostic factor, and an aggressive surgical approach should be advocated.