Major Clinical Response to Afatinib Monotherapy in Lung Adenocarcinoma Harboring EGFR Exon 20 Insertion Mutation

Here, we present the case of a patient with exon 20 insertion carrier NSCLC with strikingly differential responses to first- and second-generation TKI treatments (Figure 1A). In June 2016, a 61-year-old male never-smoker had an abnormality discovered on a routine x-ray examination of the chest. Computed tomography (CT) scan set up the preliminary diagnosis of pulmonary tumor in the superior lobe of the left lung with metastases in the right upper lobe and in the left lung (Stage IVa, T2N0M1a) (Figure 1B). In June, tumor mass reductive surgery was performed, although complete excision was not possible. His diagnosis was well-differentiated lung adenocarcinoma. Positron emission tomography (PET) scan showed a residual suspicious lesion in the right upper lobe (80 × 34 mm); fine needle aspiration cytology results confirmed metastasis of the excised adenocarcinoma. The presence of an exon 20 insertion, EGFR-H773_V774insNPH (also referred to as: EGFR-N771_H773dup; genotype c.2319_2320insAACCCCCAC) was detected in the histologic sample by Sanger sequencing.