EGFR T790M mutation after chemotherapy for small cell lung cancer transformation of EGFR-positive non-small cell lung cancer

• Main Authors: Tomoaki Sonoda, Shingo Nishikawa, Rie Sakakibara, Masafumi Saiki, Ryo Ariyasu, Junji Koyama, Satoru Kitazono, Noriko Yanagitani, Atsushi Horiike, Fumiyoshi Ohyanagi, Hironori Ninomiya, Yuichi Ishikawa, Makoto Nishio
• Format: Article
• Language: English
• Published: Elsevier 2018-01-01
• Series: Respiratory Medicine Case Reports
• Online Access: http://www.sciencedirect.com/science/article/pii/S2213007117303921

In non-small cell lung cancer (NSCLC) with an epidermal growth factor receptor (EGFR) mutation, 50%–65% of cases acquire resistance after treatment with EGFR-tyrosine kinase inhibitors (EGFR-TKIs) because of an EGFR T790M point mutation and 3%–14% of these cases transformed to small cell lung cancer (SCLC). Generally, the EGFR T790M secondary mutation develops with ongoing ATP competitive inhibition. We present a case of a 76-year-old woman with lung adenocarcinoma harboring an EGFR-L858R mutation who received first-line gefitinib and developed SCLC transformation. She was administered several chemotherapy agents, including a platinum doublet. The primary lesion that showed SCLC transformation had reconverted to adenocarcinoma with EGFR L858R and T790M mutations at the time of a second re-biopsy. Therefore, she was administered osimertinib, which resulted in clinical remission. This case suggested that serial biopsies are necessary even after SCLC transformation. Keywords: NSCLC, EGFR mutation, SCLC transformation, T790M, Osimertinib