Few studies have investigated the prognosis of non-gastric gastrointestinal stromal tumors (GISTs) under the modified National Institutes of Health (NIH) consensus criteria in Korea. This study aims to clarify the clinical usefulness of the modified NIH criteria for risk stratification.

From January 2000 through October 2012, 88 patients who underwent curative resection for primary GISTs were included in this study. The enrolled patients were stratified to predict recurrence by the original NIH criteria and modified NIH criteria.

In all, 88 patients had non-gastric GISTs, including 82 and 6 patients with GISTs of the small intestine and colorectum, respectively. The mean age was 57.3±13.0 years, and the median follow-up duration was 3.40 years (range, 0.02-12.76 years). All patients who were placed in the intermediate-risk category according to the original NIH criteria were reclassified into the high-risk category according to the modified NIH criteria. Therefore, the proportion of cases in the intermediate-risk category declined to 0.0% from 25.0% (22/88), and the proportion of cases in the high-risk category increased to 43.2% (38/88) from 18.2% (16/88) under the modified NIH criteria. Among the 22 reclassified patients, 6 (27.3%) suffered a recurrence during the observational period, and the recurrence rate of high-risk category patients was 36.8% (14/38).

Patients in the high-risk category according to the modified NIH criteria had a high GIST recurrence rate. Therefore, the modified NIH criteria are clinically useful in selecting patients who need imatinib adjuvant chemotherapy after curative surgical resection.