T790M finally detected

Fri, 03/11/2022 - 00:47

Patient diagnosed with NSCLC EGFR+ Exon 19Del and treated with Erlotinib 150mg for 10 months until progression. Liquid biopsy was T790M negative and the subsequent tissue biopsy was 790M negative as well. Carboplatin Pemetrexed chemo for 4 cycles and progression detected and liquid biopsy was T790M negative as well. Docetaxel for 4 cycles and disease progression continued. Liquid NGS ordered and T790M (less than 1% SNV) detected along with PIK3CA and TP53. Patient started on Tagrisso 80mg on March 1, 2022. Any insight as to why to took so long for 790M to show up? Will the other mutations detect have an impact on current treatment? Thank you in advance for any insight on the matter.

JanineT Forum …

Hi and welcome to Grace. There's not always enough mutation to be caught in a sample of blood or a tissue biopsy.
Today, tagrisso is given as first line treatment and (at least often) given 2nd line no matter t790m detection especially since it is not always caught in testing.
Let me ask one of our faculty to comment further and/or correct me.
Thanks for your question and best of luck,

Dr West


It is important to note that no test is perfectly sensitive at detecting a target all the time, and this is definitely true for a "liquid biopsy", doing next generation sequencing from plasma. The technology for these tests has been improving over time, but it's less reliable in patients with a relatively low volume of disease, because it requires the ability to detect shed DNA from tumor cells. Because of this, in patients with only limited disease in the chest, it's notoriously less sensitive than it is for patients with more disease visible on scans, which correlates with more circulating tumor DNA to detect.

With regard to your question of other mutations detected, this is not yet extremely well established, but there are studies that have indicated that the duration of benefit from drugs like Tagrisso tend to be shorter in patients who also have other mutations like TP53 and/or other mutations present. However, we still treat and hope for the best result...it doesn't change our management plans.

Good luck.

-Dr. West


I am very grateful for your reply Dr. West and Janine. Looking forward to learning from your videos. Thanks also to Dr. Dagogo-Jack who convinced me in another video to insist on repeat liquid biopsy when the direction the oncologists are taking is palliative care.

JanineT Forum …

That is very exciting to hear that you can give tagrisso a chance. I don't know for sure but I feel that Grace can be at least partially credited for my husband's cancer outcome. Without a doubt, Grace helped me keep my sanity by allowing me enough insight to know he was getting the treatments best for him.

If I may point out a mistake and common misconception...Palliative care is comfort care given to anyone in need of comfort. Your docs were probably suggesting "hospice care" which is a type of palliative care but without life-prolonging, anti-cancer treatment. The terms are relatively new to medicine and have undergone some definition changes throughout the years. Always welcome palliative care, whether it's a slice of cake or acupuncture. :)

I hope you do well with tagrisso. If you need help finding anything let me know.
Best of luck,


Pet-scan revealed disease progression in both adrenal glands,L5 spine,elbows,hip bones and growth in primary lung tumor. Brain CT showed quite a number of small tumors. Patients final treatment will be radiotherapy to the L5 and will be on palliative home care until hospice care becomes necessary. Pain management is mainly Oxycontin and Oxynorm. Low dose steroids to reduce brain oedema. Not much time left.

JanineT Forum …

Oh JoJo I am so sorry. Deciding to stop treatment has got to be one of the bitterest options yet it's important to understand what that conversation would be like with the oncology team. So I'm glad you've shared this part of the cancer journey with us. We, at least in the US don't talk about death and dying and are taught to fear it unfortunately we are not shown how to approach it or talk about it. Hence we are slow to invite hospice care into the norm. Palliative and hospice care teams have end-of-life care experiences that go far beyond what most of us possess.

I wish your person and you peace,