Transcript
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Janet Freeman-Daily:
Okay. So initially, we’ve just been talking about biomarker testing for initial diagnosis. Say a patient is on a targeted therapy, and the therapy then begins to fail, or they stop developing—they start developing other sites. Do we ever go back and do molecular testing to find out if they’ve developed a different cancer?
Dr. Camidge:
Essentially, acquired resistance after you benefit occurs in two main ways. Either you stop delivering the drug to the target, so that’s usually what happens when you’re progression occurs in your brain. You’re just not getting exposure. Or in the environment of the drug in your body, evolution has taken place. So there’s diversity in your cancer. There are different clones within it. The environment has the drug. And then, clones, which have the ability to grow, and that gets selected out. So imagine we’re on the Galapagos Islands. There are finches flying around.
We change the environment on one of those islands. And, gradually, the population of finches changes. And that’s what goes on in the cancer, and we can rebiopsy and reanalyze and see how it’s changed—see if the beak of the cancer has changed.
Janet Freeman-Daily:
If a patient is on a targeted therapy and progresses, and they change to something else, say chemo, can they ever become sensitive to that initial drug again?
Dr. Camidge:
Yeah, because you change the environment, so it adapts to the immediate environment. So it will now try and select clones, which have an advantage in the presence of chemotherapy. And if you stop the targeted therapy, assuming those mechanisms of resistance are not completely overlapping, that will fade away. And the chemo-resistant clone will—will—will gradually fade in.
Janet Freeman-Daily:
Okay. So, Nisha, are there any biomarkers we can use to test to see if a particular drug is being effective for a patient? I believe there was something that was shown as to whether or not certain patients would—could respond to EGFR.
Dr. Mohindra:
The way that I use a lot of the biomarkers are at the time of resistance. There is looking for the T790M mutation. In terms of looking to whether someone is sensitive, I usually—if they have a sensitizing mutation on their testing, that’s what I will utilize. Can you…
Janet Freeman-Daily:
I probably didn’t ask—ask the question very well. And maybe there isn’t a good answer to this. Are there any biomarkers we use to show whether or not a treatment is working?
Dr. Camidge:
Oh, like a pharmaco dynamic—you mean other than do you feel better, and does the scan look better?
Janet Freeman-Daily:
Yes.
Dr. Camidge:
Something fancier than that.
Janet Freeman-Daily:
Yes.
Dr. Mohindra:
Right. I mean, not in—in clinical practice. I think those—those are avenues that are going to be explored, especially with liquid biopsies moving forward. Is there a way to track your cancer? But I think, right now, the way it stands, not really, unless you guys…
Dr. Camidge:
Well, so, you know, this—people get religious beliefs on this. So I do use circulating serum tumor markers. And we, actually, have a paper that is—we’re just preparing on it. So we can find things that have names like CEA, CA125, CA199 and CA2729, which, if you look—if you Google them all, if you hit Dr. Google, they’re all associated with other cancers.
Colon cancer, ovarian cancer. But the trouble is your cancer hasn’t read the textbook. And about 90 percent of lung cancers will express at least one of these. And, you know, there are—they are an additional piece of information. So they will go up, if your cancer is progressing, and they will go down if your cancer is getting better. People have tried to use, you know, what’s recently called liquid biopsies. So it’s a very high-tech version of, essentially, the same thing where you’re measuring the—is that your next question?
Janet Freeman-Daily:
You read my outline.
Dr. Camidge:
I did not. I can’t even read that. You have to hold it up. All right. You can measure the quantity, let’s say, of your EGFR mutation. And you can show it goes down, and then it comes back up, which is, essentially, the same thing. It’s just, you know, 10 times more expensive and seems more high tech and will suffer the same, you know, slings and arrows of people saying well, you know, what does this tell you? It’s not a substitute for the scans. You can get mixed responses.
But, you know, they’re all—you know, there’s no one, you know, convicting piece of evidence. There’s lots of circumstantial evidence, and you take it all together when you make clinical decisions.
Please remember the opinions expressed on Patient Power are not necessarily the views of our sponsors, contributors, partners or Patient Power. Our discussions are not a substitute for seeking medical advice or care from your own doctor. That’s how you’ll get care that’s most appropriate for you.
Published By :
Patient Power
Date :
Dec 27, 2016
