Resistance to Both Chemotherapy and EGFR-TKI in Small Cell Lung Cancer With EGFR 19-Del Mutation: A Case Report.

Epidermal growth factor receptor (EGFR) mutations are common in non-small cell lung cancers, but rare in small cell lung cancers (SCLCs). In previous reports, some SCLC patients with EGFR mutations could benefit from EGFR tyrosine kinase inhibitors (TKIs). In this study, we reported a case in which an SCLC patient with EGFR exon 19 deletion (19-Del) mutation did not benefit from EGFR-TKIs. Interestingly, the standard treatment strategies for SCLC also failed to control tumor progression. Moreover, we screened 43 SCLC patients in China and found that the frequency of EGFR mutations in Chinese SCLC patients was about 4.65% by next-generation sequencing (NGS). Collectively, this case illustrated a rare subtype of SCLCs which harbored EGFR mutations and was intrinsically resistant to standard treatments and EGFR-TKIs. We also tried to explore the mechanisms underlying drug resistance. The literature concerning SCLCs with EGFR mutations is reviewed.

Lung Adenocarcinoma Harboring EGFR Kinase Domain Duplication (EGFR-KDD) Confers Sensitivity to Osimertinib and Nivolumab: A Case Report.

BACKGROUND: Kinase domain duplication of EGFR (EGFR-KDD) is a rare oncogenic driver alteration and serves as a potential therapeutic target. Its effect on EGFR-tyrosine kinase inhibitors (TKIs), especially the third-generation drug Osimertinib, and immune checkpoint inhibitors (ICIs) remains inconclusive. CASE PRESENTATION: A 45-year old male with lung adenocarcinoma progressed with liver metastasis after receiving pemetrexed and cisplatin as adjuvant chemotherapy. Targeted next-generation sequencing (NGS) identified an EGFR-KDD in the resected left upper lung. Icotinib was used in the following treatment and the liver metastasis was found to shrink but the progression-free survival (PFS) only lasted for 4 months with the appearance of right hepatic metastasis. Meantime, the same EGFR-KDD was identified in the left hepatic re-biopsy. Afterward, the patient benefited from the third-line therapy of Osimertinib with a PFS as long as 21 months. Then he progressed with enlarged mediastinal lymph nodes, and targeted NGS consistently identified EGFR-KDD, as well as a new RELN p.G1774E mutation. Given the continually increasing tumor mutation burden (TMB, 3.4 mutation/Mb) and PD-L1 expression-based tumor proportion score (TPS, 1%), Nivolumab was used as the fourth-line salvage therapy, which lead to considerable efficacy, with decreased blood carcinoembryonic antigen (CEA), regressed mediastinal lymph nodes, and reduced liver metastases. CONCLUSIONS: Our case provided direct evidence to support the role of Osimertinib in the treatment of EGFR-KDD, as well as added valuable insights into application of immune-based therapeutics in the specific subgroups bearing EGFR alteration(s).