2017 Volume 57 Issue 3 Pages 211-215
Background. Osimertinib is generally effective for T790M-positive epidermal growth factor receptor (EGFR) gene-mutant non-small cell lung cancer. Case. A 77-year-old female was diagnosed with lung adenocarcinoma in the lower lobe of the left lung harboring a 15-base-pair deletion in exon 19 (ex19 15-bp del) of the EGFR gene. Another nodule was detected in the right lower lobe. She had received gefitinib as a first-line treatment for two years, which resulted in shrinkage of both lesions. After disease progression occurred during gefitinib administration for one year, afatinib was consequently administered for another year; however, afatinib was also ineffective. A transbronchial re-biopsy for the left primary lesion revealed the existence of ex19 15-bp del and T790M double mutations. Osimertinib induced the clear shrinkage of the primary lesion and no change in the right lung lesion. However, right pleural effusion appeared and progressed, and the findings of the effusion were ex19 15-bp del-positive and T790M-negative. Left hydronephrosis developed two months later, and right hydronephrosis occurred three months after that, thus requiring percutaneous renal pelvis drainage. The patient was lost due to the progression of lung cancer at four months after osimertinib initiation. Conclusion. Treatment with osimertinib can occasionally result in different responses from multiple lesions because of the spatial heterogeneous T790M status of tumor cells in non-small cell lung cancer harboring an EGFR gene mutation.
