Because gastrointestinal stromal tumor (GIST) has an estimated incidence of 3,300 to 6,000 new cases per year in the United States, comprising less than 1% of all gastrointestinal tumors, the rarity of this tumor type can make it more challenging for oncologists and other members of the cancer care team to stay up to date on the latest treatments. Michael C. Heinrich, MD, lead investigator of the phase 1 NAVIGATOR trial, recently spoke with i3 Health about the FDA's approval of avapritinib (AyvakitTM, Blueprint Medicines) for adults with unresectable or metastatic GIST with platelet-derived growth factor receptor alpha (PDGFRA) exon 18 mutations. The approval provides a promising treatment option for patients with this mutation, which has been linked to resistance to standard GIST therapies. In this second installment of his interview with i3 Health, Dr. Heinrich shares advice for oncologists regarding the best ways to help their patients with GIST.
How does the treatment of GIST still need to evolve?
Michael Heinrich, MD: I think the thing that really needs to evolve is something that should have evolved already: oncologists need to have GISTs tested to figure out what's wrong. We've been trying to get this message out for 15 years. We thought we were maybe getting up to 50% or 60% testing, and then a study was published recently by Dr. Florindez and Dr. Trent from the University of Miami saying that only 26.7% of GIST tumors in the United States are currently being molecularly profiled. That's a big problem: if we don't profile to find these PDGFRA exon 18 mutations, then we're going to be treating the patients inappropriately, giving them drugs that will not work and not going to the drug that would work, which, for patients with PDGFRA exon 18 mutations, is avapritinib. I'm hoping that going forward, this approval will finally shake oncologists up enough to do the testing that we should have already been doing.
What do you feel are the most significant challenges of treating with patients with GIST?
Dr. Heinrich: Well, I think it's the other way around: the patient has the challenge, not the doctor. GIST is an uncommon disease. There are 6,000 new cases in the United States every year, and probably about half of those turn out to be metastatic at some point. For the average GIST patient going to an oncologist, their oncologist likely has 0 to 2 GIST patients, so it's hard for oncologists to be totally on top of the new treatment developments. I think that the patients banding together and forming patient advocacy groups and patient education organizations––those organizations have educated the patients so that they can go in to see their oncologist and say, "Look, there's this new drug. I need my tumor tested." It just gives them the questions to ask their oncologists that sometimes will get the patients to a better place.
Honestly, though, if patients have more complicated situations, sometimes they would benefit from seeing a GIST specialist. Again, these patient advocacy groups generally try to vet doctors in different states in the United States and publish lists of doctors who they think are especially qualified to take care of GIST patients.
Do you have any words of advice for community oncologists who are treating patients with unresectable or metastatic GIST?
Dr. Heinrich: In real estate, we say location, location, location. In GIST, I say mutation, mutation, mutation. Please perform mutation testing. Using that information and the National Comprehensive Cancer Network (NCCN) guidelines, or now the package insert for avapritinib, I think we can get to a better place of how patients are being treated so that they get the right drug and the right dose.
About Dr. Heinrich
Michael C. Heinrich, MD, a medical oncologist, is a Professor of Medicine at Oregon Health & Science University. Dr. Heinrich is involved in both preclinical and clinical research, with his work ranging from the identification of novel molecular targets to the testing of new agents in clinical trials. His primary research interest lies in the development of novel tyrosine kinase inhibitors. His investigations into new treatments for GIST and other cancers have been published extensively.
For More Information
To gain additional expert perspectives from Dr. Heinrich, read the first installment of this interview regarding the approval of avapritinib for PDGFRA exon 18-mutated GIST.
Transcript edited for clarity. Any views expressed above are the speaker's own and do not necessarily reflect those of i3 Health.