Dynamic changes in pathology and PD-L1 expression in a patient with metastatic lung adenocarcinoma who received pembrolizumab therapy followed by two salvage surgeries two years later: A case report.

During chemotherapy, certain cancer cells undergo cell death, which alters the properties of remaining cells and leads to numerous changes in the constituent cells of lung cancer. Immunotherapy has been used as neoadjuvant therapy, and several studies have reported changes in lung cancer tissue following treatment with immuno-anticancer drugs in early stage disease. However, no research has currently discussed the pathological and PD-L1 expression changes in metastatic lung cancer. Here, we describe a patient with lung adenocarcinoma and multiple metastases who achieved complete remission after receiving initial carboplatin/pemetrexed followed by pembrolizumab treatment for 2-years. The initial biopsy revealed adenocarcinoma with high PD-L1 expression, and next-generation sequencing (NGS) identified KRAS, RBM10, and STAG2 mutations. After 2-years of treatment with pembrolizumab, the patient achieved complete response (CR). The patient underwent first salvage surgery for the oligo-relapse lesion, and the pathology result showed a large cell neuroendocrine tumor (NET) with adenocarcinoma and no PD-L1 expression. NGS revealed KRAS and TP53 mutations. After one year, a chest computed tomography (CT) scan revealed a small nodule in the right lower lobe, and the patient underwent second salvage surgery. Pathology results showed minimally invasive adenocarcinoma with no PD-L1 expression and no significant genetic mutations. This case report demonstrates the dynamic changes cancer cells undergo following pembrolizumab treatment and salvage surgeries and is the first report to compare pathological changes after immunotherapy and two subsequent salvage surgeries in metastatic lung adenocarcinoma. Clinicians must remain vigilant to these dynamic changes throughout treatment and consider salvage surgery for oligo-relapse lesions. By understanding these changes, new strategies can be developed to improve the long-term efficacy of immunotherapy.