REMINDER Targeted Therapies Patient Forum

Tue, 07/06/2021 - 11:22


Dear Janine, 

sorry to bother you but we need your help again. My mother has been on tagrisso since nov 2020. Stage 4 egfr with one brain met and primary lung tumor. 

her pet scans in February 2021 and june 2021 showed a complete response and we are very happy. However she did a "cancer track" liquid biopsy test in april 2021 which showed a new mutation called TYMS and the earlier TP53 was still present. However the EGFR mutation had disappeared. Then she did a pet scan in june which was clear.  The liquid biopsy also showed a high circulating tumor cell count of 4 (down from 7 last year when diagnosed). 

last week she had a sudden low sodium level and we thought maybe she might have had progression.  Her next pet scan is scheduled for December and we are wondering if she should do it earlier. Her doctor thinks we should not change it. Also he is not a keen on a ct scan saying that it does not show metabolic activity.  

What would you do in such a situation? Would Dr West recommend doing an earlier pet scan? thank you in advance. You have been of immense help so far. We can insist on earlier scans if we want. Her ESR, CRP, CEA Levels are all normal. 

kind regards 


JanineT Forum …

Hi Rowan,  It's fine to wait for the scan unless she is having new or worsening symptoms.  While a PET/CT is fine, the pet manufacturers were never able to prove better outcomes when used in following lung cancer.  They help in the staging process but if stage IV is already evident it's not helpful to find more eariler than a CT can, though it can add lots of anxiety and even cause a change in treatment earlier than needed which in turn shortens all available options.  PETs are much more expensive.  With that said, my husband's onc insisted on using pet/ct which was not a battle I needed to fight as long as I had the info. 


I've asked for faculty input on standards of how to proceed with info on low sodium.  Is you mother having symptoms of hyponatremia?


Take care,






yes she was 'feeling bad' so we did the basic blood tests her doctor usually does and found low sodium at 126. Her normal level was hovering at 135. She reduced her water intake and added some salt to her meals and its now back up at 134. We are concerned with the sudden cause of low sodium. 

i got another opinion from an oncologist and she said to get a chest ct done as it will be useful. 



JanineT Forum …

I'm sorry rowan for the delay.  I don't think this answers the question of why.  That's not something we can do.  Though here is the thought process from Dr. Desai,


"I have a few questions:

  1. How low is the sodium
  2. What has the trend in sodium been, does she have a lower normal at baseline?
  3. As you asked, are there any symptoms?


As you know, Tagrisso can cause hyponatremia, which is graded from 1-5 as follows" (sorry but couldn't paste the graph from Dr. Desai but 134 appears to be above grade 1 and 125 without symptoms 2 and with symptoms grade 3)

Dr. Desai continued, "In clinical trials they had hyponatremia within all grades about 30%, but grade 3-4 was only 3%, if her numbers fall in grade 1-2 range, we can check it weekly or so to ensure it is stable ofcourse things will change if she has symptoms.

I hope that is helpful."


Weekly checks appear to be in order since her numbers have moved back to the normal range. 


Hello Janine, 


thank you very much for clearing that up. I did not know that tagrisso caused low sodium. She was at 126 two weeks ago and now its within normal range. 

I will contact you if i need further help. Thanks again. 

kind regards