ERBB4 and small cell lung carcinoma: Afatinib differs from first-generation EGFR-TKIs in binding and blocking the ErbB family that inhibits EGFR, HER2, and HER4 irreversibly as shown in basic studies.[6–8] Moreover, afatinib therapy was superior to gefitinib in clinical research with respect to PFS and ORR.[10] The emergence of T790M might show a greater increase during afatinib therapy than during gefitinib therapy, while resistance mechanisms differing from T790M, MET amplification, and transformation to small cell lung cancer might emerge.