A modification of NIH consensus criteria to better distinguish the highly lethal subset of primary localized gastrointestinal stromal tumors: A subdivision of the original high-risk group on the basis of outcome

Abstract

By reappraising the National Institutes of Health (NIH) consensus criteria, we worked on establishing a modified scheme to identify highly lethal gastrointestinal stromal tumors (GISTs), which have an imperative demand for sequencing analysis to assess the suitability of an adjuvant imatinib trial. Clinicopathologic features, including NIH and modified schemes, were retrospectively analyzed for 289 patients with localized GISTs. We combined the very low/low-risk GISTs into a single "risk level I" group (<or=5 cm, <5/50 high power fields [HPFs]) and redesignated the intermediate-risk GISTs as "risk level II" (either <5 cm, 6 to 10/50 HPFs or 5 to 10 cm, <5/50 HPFs). The GISTs of "risk level IV" group were >5 cm and >10/50 HPF, with the rest of high-risk GISTs defined as "risk level III." The cumulative 5-year rate of disease-specific survival (DSS) for all 289 patients was 82%, and the DSS rates for patients with GISTs classified as risk levels I to IV were 100%, 96%, 67%, and 25% at 5 years, respectively. The prognostic differences were striking between the risk level II and III groups (P < .0001) and between the risk level III and IV groups (P = .0002). The higher risk level of our scheme represented the strongest independent adverse factor (risk ratio [RR] = 11.299 for risk level III; RR = 33.815 for risk level IV; P < .0001), followed by mixed/epithelioid histology (RR = 2.837, P = .003) and older age (>or=70 years, RR = 1.955, P = .044). Remarkable prognostic heterogeneity exists in the high-risk category of the NIH scheme, which is not as effective as the modified criteria in identifying highly lethal GISTs that we classified as risk level IV.