Metastasis and lymph node spread in gastric gastrointestinal stromal tumors

While surgical excision is the treatment of choice for many patients with larger Gastrointestinal Stromal Tumors (GISTs), some patients with smaller tumors may be candidates for surveillance or minimally invasive endoscopic resections. This study examined the incidence and predictors of metastasis and lymph node (LN) spread for gastric GISTs in a large national database. Cases were abstracted from the National Cancer Database (NCDB) from 2004-2015. Exclusion criteria included cases with unknown patient, tumor, or management characteristics, presence of other cancers, and patients with chemotherapy, immunotherapy, or radiation preceding surgery. Univariate and multivariate analyses were performed using SAS JMP to characterize the relationship of patient gender and age, and tumor size and mitotic index, with metastasis or LN spread. Cases were stratified by size and mitotic index to examine the incidence of metastasis or LN spread. 14,979 cases of gastric GIST were identified in the NCDB. There were 5,069 cases in the analysis cohort after exclusions. Univariate analysis revealed that tumor size (P<.0001), mitotic index (P<.0001), and age less than 40 years compared to greater than 40 years (P<.0001) were predictors of metastasis or LN spread. On multivariate analysis, size >5 cm compared with ≤5 cm (OR 7.79: CI 4.95-12.26 [P<.0001]), high mitotic index compared with low mitotic index (OR 2.19: CI 1.57-3.06, [P<.0001]), and age <40 years compared with >40 years (OR 2.91: CI 1.77-4.78, [P<.0001]) were all independent predictors of metastasis or LN spread. There was no significant association with gender. Regardless of mitotic index, gastric GISTs ≤2 cm and those 2-5 cm in size had an incidence of metastasis or LN spread of <2% (Fig. 1). For gastric GISTs, size and mitotic index are strongly associated with metastasis and LN spread. Gastric GISTs ≤5 cm, regardless of the mitotic index, have a very low risk of nodal spread and metastasis. This subgroup may be more appropriate for minimally invasive resections. Larger gastric GISTs, particularly those with a high mitotic index, are at increased risk for metastasis or lymph node spread, and surgery with lymph node dissection may be indicated for patients who are surgical candidates.