John L. Marshall, MD
Treating patients with newly diagnosed metastatic colorectal cancer (mCRC) requires great foresight, explained John L. Marshall, MD.
State of the Science Summit™ on Gastrointestinal Cancers, Marshall, chief, Division of Hematology/Oncology, Medstar Georgetown University Hospital director, Otto J. Ruesch Center for the Cure of Gastrointestinal Cancer, Georgetown-Lombardi Comprehensive Cancer Center, discussed the current and future scope of mCRC.
OncLive: What is the importance of molecular profiling in patients with newly diagnosed mCRC?
: Molecular profiling is critical in frontline metastatic colon cancer. You need to know that right from the beginning. You have to know MSI, RAS, BRAF, HER2
, and NTRK
. Most physicians are doing broad molecular profiling. [In my presentation tonight], I also made the point of [differentiating between] left- versus right-sided tumors. In right-sided colon cancer, EGFR therapies don't seem to work as well. In left-sided colon cancers, it’s really important to know all of the molecular testing. If your patient is in that left-sided RAS
wild-type group, there are retrospective data looking at EGFR-targeted therapy. In that 20% of patients, the data suggest that there may be a benefit to using those drugs in that space. In the rest of patients, it probably doesn't matter. You can give everyone FOLFOX and bevacizumab (Avastin), but in that group you need to think twice about EGFR therapy.
Should HER2 amplification be accounted for on molecular profiling panels?
is a critical thing to look for in CRC, and how one measures it probably matters. Certainly, the higher the gene amplification, the more responsive [the patient will be to therapy]. Most physicians use immunohistochemistry. Those patients with high [HER2] expression seem to be the ones who benefit.
expression. You have to look for it.
What has been the impact of immunotherapy in patients with MSI-H as well as microsatellite stable tumors?
You have to know the MSI status of every patient with colon cancer, regardless of stage. Most of us test this using immunohistochemistry first, but you can do this with next-generation testing. Tumor mutational burden helps confirm that. You need that signal in colon cancer for immunotherapy to even be in play. It's not common, so you have to keep looking to find it. Most of your patients will not have that.
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