The influence of STK11 mutation on acquired resistance to immunotherapy in advanced non-small cell lung cancer with Lynch syndrome: a case report and literature review

Immune checkpoint inhibitors (ICI) monotherapy or combination therapies have become increasingly popular in patients with advanced non-small cell lung cancer (NSCLC). However, there are still many unknowns concerning the predictive bio-markers and resistance mechanisms to immunotherapy. Patients with primary tumor STK11 mutation reportedly to have a lower response rate than the STK11 wildtype and possibly a primary resistance mechanism to ICIs. However, there is presently no data regarding the contribution of STK11 to acquired resistance to ICIs. Herein we report on a patient who was diagnosed with advanced lung squamous cell carcinoma accompanied by Lynch syndrome. The patient developed an STK11 mutation after receiving pembrolizumab as a first-line treatment. Programmed death ligand 1 (PD-L1) was highly expressed (50%) in the biopsy. HRAS Q61L and TP53 R158L were mainly detected. Unexpectedly, the patient carried an MSH6 heterozygous germline mutation, and was classified as proficient mismatch repair (pMMR). The patient subsequently received pembrolizumab (200 mg, ivgtt, q3w) as first line therapy and achieved stable disease (SD) as the best response. After eight treatment cycles, the patient suffered disease progression (PD), and an STK11 frameshift mutation was newly identified in his plasma circulating tumor deoxyribonucleic acid (ctDNA). This case study suggests that STK11 could contribute to pembrolizumab acquired resistance. Furthermore, the patient was also diagnosed with Lynch syndrome, which rarely occurs in lung cancer.