In Response: We read with great interest the comments of Cheung et al. and understand the nature of their criticisms. Their primary concern centers on the exclusion of patients who may have had gastrointestinal stromal tumor (GIST) but were potentially misclassified within the Surveillance, Epidemiology, and End Results (SEER) database, especially before the year 2000. The implication is that some sort of selection bias has occurred. The nature and the source of the purported selection bias, however, are not made clear. Having carefully considered their comments, we reaffirm that what Cheung et al. call a “major design flaw” was actually a carefully considered, hypothesis-based exclusion of cases in light of the realities and limitations of the SEER database.

With respect to the issue of the appropriate classification of GIST, we recognize that GISTs were misclassified to a large degree in the 1990s, and that only with further understanding of the...

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