Abstract
Objective This study aimed to compare the tumor characteristics and long-term outcomes between EGIST and GIST. The confounding function was applied to improve the result credibility in the case of small sample size. Design, Setting, and Participants. This cohort study enrolled 55 patients with EGIST who underwent surgery and were selected from four high-volume hospitals in China and 221 GIST patients who were collected from one of the four hospitals between January 2006 and September 2017. We used propensity score matching (PSM) and subgroup analysis to compare EGIST with GIST in terms of prognosis. The confounding function was used for sensitivity analysis to reduce unmeasured confounding. Results We matched 43 patients in each of the GIST and EGIST groups by PSM. We compared EGIST data with GIST data to explore the prognostic factors between them. In the multivariate Cox regression model, tumor location of EGIST was negatively correlated with overall survival (after PSM: HR, 4.32; 95% CI, 1.22–15.26) or disease-free survival (after PSM: HR, 9.79; 95% CI, 2.22–43.31), which was also intuitively shown in the Kaplan–Meier survival curves (all P values < 0.05). In the subgroup analysis, EGIST with high risk factors had a worse prognosis than GIST. In unmeasured confounding analysis, the overall curve tends to show all combinations of c(0) of c(1) up to 2.0, none of which would bring the corrected relative risk to 1 for OS and DFS. Conclusions and Relevance. EGIST was associated with worse prognosis compared with GIST patients, particularly in EGIST patients with high risk factors, while there was a similar prognosis without those high risk factors.
Highlights
Extragastrointestinal stromal tumor (EGIST) is mainly located in the nongastrointestinal tract and is rarer compared to the gastrointestinal stromal tumor (GIST) [1]
Before propensity score matching (PSM), EGIST tended to have worse factors compared to GIST, suggesting that EGIST may be a worse malignant tumor. e median surgical time was 152 min in EGIST and 136 min in GIST. e median surgical bleeding was 100 mL in EGIST and 50 mL in GIST. ere was an obvious difference between the two, suggesting that EGIST resection is more difficult than GIST, owing to some special location
Other factors associated with GIST with overall survival (OS) or disease-free survival (DFS) in previous analysis were not statistically significant after PSM; we will inevitably think that tumor location has too much influence on OS or DFS to cover up other factors
Summary
Extragastrointestinal stromal tumor (EGIST) is mainly located in the nongastrointestinal tract and is rarer compared to the gastrointestinal stromal tumor (GIST) [1]. Several previous studies have sought the difference of EGIST from GIST using only the GIST data [7,8,9,10,11,12,13], while others have illustrated EGIST features without those data [2,3,4,5,6, 14]. Those have suggested that EGIST was negatively associated with prognosis. The therapeutic strategy of EGIST is with reference to the treatment of GIST and has poor prognosis in previous studies [2,3,4,5,6]
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