Prediction of morbidity following cytoreductive surgery for metastatic gastrointestinal stromal tumour in patients on tyrosine kinase inhibitor therapy.

BackgroundAlthough cytoreductive surgery has been shown to be beneficial in carefully selected patients with metastatic gastrointestinal stromal tumours (GISTs) treated with tyrosine kinase inhibitors (TKIs), factors predictive of postoperative morbidity have not been investigated previously. Methods: A surgical complexity score for GIST metastasectomy (GM-SCS) composed of patient-related and surgical factors was assigned retrospectively to patients with metastatic GIST treated with TKI therapy and surgery at two institutions between 2002 and 2014. The ability of clinicopathological factors and GM-SCS to predict postoperative morbidity was assessed by means of a multivariable logistic regression model. Postoperative complications were categorized using the Clavien-Dindo classification. Results: Some 400 operations on 323 patients with metastatic GIST on TKIs were included. Complications were observed following 110 operations (275 per cent) including 70 major complications (grade III-V) (175 per cent of 400 operations). Patients were divided into low (5 points or less; 100 patients, 250 per cent), intermediate (6-9 points; 191, 478 per cent) and high (at least 10 points; 109, 273 per cent) complexity scoring groups based on the GM-SCS. An intermediate (odds ratio (OR) 288; P = 0008) and high (OR 540; P < 0001) GM-SCS were independent predictors of overall complications, whereas only a high GM-SCS was independently predictive of a major complication (OR 365; P = 0018). Metastatic mitotic index was also an independent predictor of overall complications (OR 255; P = 0047). GM-SCS did not predict progression-free or overall survival. Conclusion: A gastrointestinal stromal tumour metastastectomy surgical complexity score can predict morbidity, which may help in preoperative risk stratification and optimal treatment planning.