Adherence to the guidelines and the pathological diagnosis of high-risk gastrointestinal stromal tumors in the real world

Background: A multidisciplinary approach based on guidelines and pathological diagnosis by specialized pathologists are important for improving the prognosis and QoL of GIST patients. This study examined the adherence to the guidelines and the concordance of the pathological diagnosis of high-risk GISTs. Patients and methods: Among 541 patients with high-risk GISTs recruited to the prospective registry between Dec. 2012 and Dec. 2015, 534 patients were analyzed after central pathology with KIT and DOG1 IHC and genotyping of KIT and PDGFRA. Results: Of the 534 patients, 432 (81%) received imatinib adjuvant therapy at a starting dose of 400 or 300 mg/day. Multivariate analysis indicated that age (HR 0.71; 95% CI 0.58–0.88), tumor size (HR for > 10 cm vs < 5 cm, 3.87; 95% CI 1.72–8.74), mitosis (HR for > 10 vs < 5, 3.54; 95% CI 1.84–6.79), tumor rupture (HR 3.69; 95% CI 1.43–9.52) and performance status (HR 0.55; 95% CI 0.31–0.99) were independently related to adjuvant therapy. Among the 534 high-risk GISTs diagnosed locally, 19 tumors (3.6%) were diagnosed as non-GISTs, and the other 93 (18.1%) GISTs were reclassified into lower risk categories by central pathology. Among 10 patients with non-GISTs and 8 patients with PDGFRA D842V mutations, 4 (40%) and 3 (38%) patients, respectively, continued the therapy after receiving the central pathology results. Conclusions: The adherence to guidelines and the concordance of pathological diagnoses were comparatively good for high-risk GISTs. Central pathology may contribute to improved diagnosis, but further refinements may be required.