Wild-type GIST: Who does it affect and where does it typically originate?

Wild-type (WT) gastrointestinal stromal tumours (GIST), though rare, tend to develop more frequently in older adults and commonly originate in the stomach or small intestine, a recent study has found. Though treatment options are limited, surgical resection and systemic therapy remain the principal modalities.

Drawing from the US National Cancer Database, the researchers assessed 244 patients in order to determine the clinicopathological features, treatment patterns, and other correlates of wild-type GIST. Kaplan-Meier analysis and Cox proportional hazards models were used to identify factors associated with disease outcomes.

Patients were diagnosed at a median age of 59 years, and most were male and Caucasian. The most common primary site was the stomach (n=139; 57.0 percent), followed by the small intestine (n=86; 35.2 percent), colon (n=8; 3.3 percent), oesophagus (n=5; 2.0 percent), rectum (n=5; 2,0 percent), and appendix (n=1; 0.4 percent).

Tumours were generally large, most of which had diameters exceeding 5 cm (43 percent); meanwhile, only 5 percent were 2 cm or smaller. Majority of patients (85 percent) were treated through surgical resection, which resulted in negative margins in 83.7 percent of cases. Fifty-three percent of patients received systemic therapy.

Only patients with stomach and small intestine primary tumours were eligible for overall survival (OS) analysis, which found that tumours originating in the small intestine significantly decreased OS, as did those that were highly mitotic.

“­This study adds to the growing global literature on WT GIST disease to further dispel the misconception that patients with WT GIST are predominantly paediatric aged, female, and limited to the stomach. ­The importance of accurate and complete molecular characterization of GISTs among patients across the age spectrum is important to identify and most appropriately treat patients,” the researchers said.