Pembrolizumab and chemotherapy in non‐small cell lung cancer with EGFR ex20ins mutation: A case report

The efficacy of immunotherapy in non‐small cell lung cancer (NSCLC) with uncommon epidermal growth factor receptor (EGFR) mutations is not well clarified, even though immunotherapy has brought revolutionary improvements in EGFR wild‐type NSCLC. In addition, pseudoprogression has increased the difficulty in immunotherapy management and data on the incidence of pseudoprogression in patients with EGFR exon 20 insertions (ex20ins) is rarely reported. Here, we discuss the case of an advanced lung adenocarcinoma patient with EGFR ex20ins alteration. The patient received pembrolizumab plus chemotherapy as first‐line therapy and disease control was achieved. Progression‐free survival (PFS) was 9 months. The patient was subsequently treated with pembrolizumab plus docetaxel and bevacizumab as second‐line therapy and the disease remained stable. After two cycles of first‐line treatment, the patient showed improvement in performance and the primary left upper lung lesion was stable; however, there was an increase in size as well as number of small diffuse bilateral pulmonary nodules. Therapy was maintained with the original regimen and complete regression of the bilateral lung nodules was achieved after a third cycle of treatment. Pseudoprogression was diagnosed. In the case reported here, we advocate the use of a PD‐L1 inhibitor plus conventional chemotherapy in advanced NSCLC patients harboring EGFR ex20ins mutation and hope that our experience might be beneficial to other clinicians in distinguishing pseudoprogression from true progression.