Prognostic factors affecting survival after surgical resection of gastrointestinal stromal tumours: a two-unit experience over 10 years

BACKGROUND: Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal neoplasm of the gastrointestinal (GI) tract which has only been recently described based on their specific immunohistochemistry and the presence of particular KIT-related mutations which potentially make them targets for tyrosine kinase inhibition. METHODS: Sixty-one patients (29 M; 32 F, median age 60 years; range: 23–86 years) between June 1994 and March 2005, were analyzed from two allied institutions. Patient, tumour, and treatment variables were analyzed to identify factors affecting survival. RESULTS: Of the 61 patients, 55 (90%) underwent complete surgical resection of macroscopic disease. The 5-year overall survival (OS) rate in the 61 patients was 88% and the 5-year disease-free survival (DFS) in the 55 cases completely resected was 75%. Univariate analysis revealed that R0 resection was strongly associated with a better OSrate (p < 0.0001). Likewise, univariate analysis also showed high mitotic count of > 10 mitoses/per 50 HPF was a significant variable in worse prognosis for OS (≤ 10 mitoses/per 50 HPF 95% 5-year OS vs. > 10 mitoses/per 50 HPF 74% 5-year OS, respectively; p = 0.013). On subsequent multivariate analysis, only high mitotic count remained as a significant negative prognostic variable for OS (p = 0.029). Among patients resected for cure, there were 8 recurrences during follow-up. The mean time to recurrence was 21 ± 10 months (range: 4–36 months). Univariate analysis revealed that mitotic count of > 10 mitoses per 50 high power fields, intratumoural necrosis, and pathological tumour size (> 10 cm in maximal diameter) significantly correlated with DFS (p = 0.006, 0.002 and 0.02, respectively), with tumour necrosis and high mitotic count remaining as independent predictive variables affecting prognosis on subsequent multivariate analysis. CONCLUSION: Most GISTs are resectable with survival principally dependent upon mitotic count and completeness of resection. Future metabolic and genetic analyses will define the role of and resistance to induction or postoperative adjuvant targeted kinase inhibition therapy.