huj123,
I too have NSCLC Adenocarcinoma with an ERBB2 (HER2) Exon 20 mutation. It is a small subset, so there aren't any targeted drugs approved at this time. I had a second opinion at MDAnderson and he spoke of Trastuzumab Deruxtecan having very positive results in NSCLC HER2+ patients. It is approved in breast and gastric cancers and is seeking approval in NSCLC. The trials available now are only 2nd line, but I would be sure to ask her oncologist about it. I am starting my chemo next week and hopefully will see some relief from the back and hip pain - where my bone mets are - and not too many side effects of the chemo. Keep fighting.