ONCAlert | 2018 ASCO Annual Meeting
Colorectal Cancer Case Studies

Charles Fuchs, MD: RAS Mutations and the Sequence of Therapies

Charles Fuchs, MD
Published Online:Apr 28, 2016
Case 2 examines a 52-year-old woman newly diagnosed with metastatic CRC who is genotyped as part of her initial work up.

Unresectable Colon Cancer with Charles Fuchs, MD and Tanios Bekaii-Saab, MD: Case 2

Unresectable Colon Cancer with Charles Fuchs, MD and Tanios Bekaii-Saab, MD: Case 1
Unresectable Colon Cancer with Charles Fuchs, MD and Tanios Bekaii-Saab, MD: Case 2
Unresectable Colon Cancer with Charles Fuchs, MD and Tanios Bekaii-Saab, MD: Case 1
Unresectable Colon Cancer with Charles Fuchs, MD and Tanios Bekaii-Saab, MD: Case 2


Once a patient’s RAS status is known, does this inform the sequence of therapies? How can RAS testing be used to inform later lines of treatment? 

In the U.S., the majority of patients receive EGFR antibodies after first line. To be clear, it's perfectly reasonable to give either bevacizumab or an EGFR antibody to patients in the frontline setting if they have a RAS wild type tumor. The practice in the U.S. has historically been to defer EGFR antibodies to later lines. Not that there's evidence that you should do it, it's just that it has been the practice. As such, all RAS testing is best done early in treatment so when you arrive at the point where you need to make a decision where there might be progression, you have in your hands to tell you whether a patient can or should receive an EGFR antibody.

Of course, if you're contemplating an EGFR antibody in the first line, you have to make sure that you can get all RAS testing quickly. I mention it because there are facilities that will do RAS testing, but it doesn't come back in a few days. Sometimes it can take a couple of weeks, and if you're pressed to start therapy and you don't yet know the RAS testing result, you may start with bevacizumab and defer on EGFR antibodies for later lines of therapy if indeed that patient is RAS wild type.

Unresectable Colon Cancer: Case 2

52-year-old woman newly diagnosed with metastatic CRC and is genotyped as part of her initial work up.

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