dear Doctors.
In my last 2 PET scans, my main LUL tumor has grown (not just increased SUV), along with a new smaller lesion in lower lobe. 2 wks ago, I had biopsy of the upper lobe to see if I have the T790M mutation in order to enter the CO 1686 study in Stanford. well, it appears that I don't have the Exon T790, and I still have the same Exon 21 L858R mutation as I had when I was first diagnosed. Could this mean that I am still sensitive to Tarceva, although not as sensitive to it as before?? There was no other mutation study done so I don't know if I have other types of mutation, and I am not sure I should ask for that to be done - would that really be fishing?? I am taking higher dose of Tarceva (75mg/50mg) with more side effects, so if my tumor still grows despite, then I will start chemo, although I feel torn between more Tarceva or chemo??
thanks
ssflxl
Reply # - December 19, 2013, 09:19 PM
Reply To: biopsy result
I don't know if you've read much of what has been written here about "acquired resistance" , but I think you'd benefit from it. I'd start here:
http://cancergrace.org/lung/2012/08/05/acquired-resistance-faq/
The biopsy doesn't tell whether someone is still sensitive to an EGFR inhibitor: what shows that is whether there is still slow progression and less disease than was present before a person started the EGFR inhibitor on which they initially responded. Acquired resistance is a relative term, not an absolute one, so many people who are progressing slowly may well still benefit from continuing on an EGFR inhibitor, potentially in combination with chemotherapy -- it's unknown if that's the best approach.
I don't know what you'd gain from a search for other mutations. I don't see a value in doing tests for which you can't do anything with the result, and beyond T790M (and perhaps even including T790M), there isn't any expected mutation result in the setting of acquired resistance that is useful in making treatment recommendations.
The link above describes the many potential options for how to proceed in the setting of limited progression, though there is no consensus on any right answer, even among experts.
Good luck.
-Dr. West
Reply # - December 19, 2013, 10:28 PM
Reply To: biopsy result
Dr. West,
Thanks for your explanation. I see what you mean by relative vs absolute resistance - probably not too many people have absolute 100% resistance. However, I didn't realize that "The biopsy doesn’t tell whether someone is still sensitive to an EGFR inhibitor".
ssflxl