Underreporting of Gastrointestinal Stromal Tumors: Is the True Incidence Being Captured?

Background: Hospital cancer registries are only required to report gastrointestinal stromal tumors (GISTs) if labeled malignant or metastatic, leading to potential loss of cases in national cancer registries. Our objective was to determine whether GISTs are underreported in the US. Methods: Retrospective review of pathology reports between 2010 and 2013 with diagnosis of GIST was performed at two academic medical centers. Recurrent GISTs were excluded. Pathology reports were cross-referenced to cases reported by each cancer registry. Risk for metastasis/death was determined according to National Comprehensive Cancer Network (NCCN) guidelines. Results: Forty-nine cases of non-recurrent GIST were identified. Only 19/49 (38.8 %) cases were reported. None of the 30 non-reported cases were labeled malignant/metastatic on final pathology. To illustrate malignant potential, these tumors were risk stratified. Most (60 %) of the non-reported cases were low risk, but there were 4 (13.3 %) cases each in the intermediate, high, and unknown risk groups. Additionally, 7/30 (23.0 %) cases were treated with tyrosine kinase inhibitors, highlighting clinical concern of malignant GIST. Conclusions: Our results show that nearly two thirds of GIST cases have been underreported, suggesting that current reporting practices underestimate its true incidence. Revision of reporting guidelines may result in a more accurate estimation of the US disease burden of GIST.