bfarz
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Posts:7
Asian woman EGFR+ exon19 mut, stable on Tarceva for 4 years, very small progression added Alimta 5 tx,
liquide biopsy for t790m (-).
Does the negative T790 with a very small progression means anything? Does it become more important if there was more progression or any amount of progression should show T790 in liquid biopsy.
Also is there liquid biopsy for PDL/PD immune check points?
Forums
Reply # - September 26, 2016, 08:10 AM
Hi bfarz,
Hi bfarz,
Although liquid biopsies have begun to gain favor among oncologists and their accuracy is pretty fair, any type of biopsy can produce a false negative, and in this situation in which the progression is slight, it is possible that only a small subset of the cancer cells have developed the T790M mutation, or that resistance has occurred due to some factor other than T790M. It is also possible that not all of your cancer cells have an activating EGFR mutation, and that those are the cells showing progression.
It is also good to keep in mind that very small progression does not necessarily warrant a change of treatment or addition to the current EGFR TKI, as Dr. West discusses here.
There are liquid biopsy tests available for PD-L1 and PD-1 expression.
JimC
Forum moderator
Reply # - September 27, 2016, 08:15 AM
Hi bfarz,
Hi bfarz,
Just a data point......
Similar to your situation, my wife has EGFR del 19 and very slow progression. We watched for over 6 months. Later on we did liquid biopsy to test for T790M and results came back negative. The next was tissue biopsy and the results came back positive. Our oncologist at SCCA mentioned similar things also happened to other patients. The company offering the liquid biopsy was concerned about the sensitivity and accuracy of its test. They went back and reviewed the liquid biospy results and concluded there were low level of T790. So whatever the threshold the company established as a yes or no answer can lead to different conclusion or what Jim referred as false negative. It is my understanding that now the company dropped the threshold.
Net, it is my understanding that the liquid biopsy is useful in order to avoid tissue biopsy and the associated risk. If the results came back negative, the next step is tissue biopsy. I don't know if a tissue can be extracted from the progression area. It might be worth while.