YO17 - A case report of EGFR T790M acquired resistant mutation in histological transition from adenocarcinoma to squamous cell carcinoma in advanced NSCLC

Date 18 December 2016
Event ESMO Asia 2016 Congress
Session Poster lunch
Topics Biomarkers
Non-Small-Cell Lung Cancer, Metastatic
Presenter Voralak Vichapat
Authors V. Vichapat, T. Reungwetwattana
  • Medical Oncology, Ramathibodi Hospital, 10400 - Bangkok/TH


Case Summary


Osimertinib was approved for treatment of T790M resistant mutation in EGFR positive metastatic NSCLC. However, its efficacy on a secondary differentiation of squamous histology was less known.

Patient history

A 60-year old Thai man presented with chronic cough. He was a light smoker for about 15 years and had already quit for 10 years. The chest CT showed a 3.1 cm solitary mass at LLL and a 1 cm mass at RUL. Percutaneous CT guided needle biopsy was performed revealing adenocarcinoma of the lung.

Course of treatment

In June 2012, the patient underwent LLL lobectomy together with RUL wedge resection. The pathological report showed moderately differentiated adenocarcinoma of the lung at LLL and RUL with 80% acinar and 20% micropapillary patterns. The final diagnosis was stage IV adenocarcinoma of lung. He received palliative chemotherapy (Paclitaxel and Carboplatin) for 6 cycles with partial response. Within a year, he had developed pleuritic chest pain. The chest CT showed multiple lung nodules suggesting a progressive disease. The mutated genes were checked to the primary tumor and it was EGFR positive (exon 19 del). He received Erlotinib for 23 months from May 2013 until progressive disease at his right femur in April 2015. Radiotherapy was given to palliate pain symptom at the femur for 2,000cGy. Re-biopsy was performed to the metastasizing site providing fibrosis due to post RT change. Afatinib was then started to control his disease. However, he had pathological fracture at his right femur in February 2016. Nail plate fixation was done along with a tissue biopsy at the surrounding soft tissue part. The pathological examination showed pure squamous differentiation harboring EGFR T790M acquired resistant mutation. His right thigh was getting worse in terms of pain, swelling, and tense. Osimertinib was then started in May 2016 with dramatically complete response in two months.


This patient is a rare case study of EGFR T790M acquired resistance in secondary squamous cell differentiation of metastatic NSCLC. Osimertinib potentially has its activity on both adenocarcinoma and squamous cell carcinoma given that the cancer is harboring T790M resistant gene.