Key Molecular Testing Remains Critical in GIST Management

Breelyn Wilky, MD, the director of Sarcoma Medical Oncology at the University of Colorado Anschutz Medical Campus in Aurora, Colorado, discusses what key molecular insights in gastrointestinal stromal tumor (GIST) management community oncologists should prioritize today.

Although rare in community settings, when GIST is encountered, identifying mutations, particularly in KIT, is crucial to guide therapy.

Wilky stresses that imatinib (Gleevec) typically produces a dramatic early response in most patients. If it doesn’t, which occurs in fewer than 10% of cases, it should prompt urgent reassessment, including a second biopsy and repeat molecular testing. She also advises that small biopsies may limit testing, and community oncologists should not hesitate to seek expert pathology review to confirm the diagnosis, especially when relying on markers like KIT and DOG1.

TRANSCRIPTION:

0:09 | I think probably the most important message to get out to our colleagues in the community is, again, you are not going to see these GISTs very often, and if you do come across one, probably the most important thing that you can do is to make sure that you have molecular testing at the time of diagnosis on the tumor, if at all possible. Some of these patients will only have biopsies performed, and they are very, very small biopsies, and so sometimes we do not get the opportunity to get good genetic testing to figure out where the mutation is in the KIT, but usually you can.

0:45 | And so let's say, if you have a patient that you are starting on imatinib therapy, or you want to and you do not have that molecular testing, it is super important to to follow that patient closely. And if imatinib does not work, recognize that that is really, really rare. That is less than 10% of patients where imatinib does not produce a dramatic response early. And so in those patients, considering a second biopsy to get that mutation testing is really, really critical. Again, we are pretty good at diagnosing KIT expression and a marker called DOG1 usually conceal the deal for securing a diagnosis of GIST, but never hesitate to send out for an expert review at a referral center, just to make 100% sure that nothing got missed.