Complete disease remission in a TP53 and KRAS co-mutated brain oligometastatic lung cancer patient after immuno-chemotherapy and surgical resection: a case report

Lung cancer is the most common primary malignancy and tends to metastasize to the brain. A multimodal approach, including systematic therapy (targeted therapy, chemotherapy, immunotherapy) and local consolidative therapy (surgical intervention, radiation therapy, ablation therapy), is essential for treatment of oligometastatic lung cancer. The systemic immunotherapy has been shown to increase response rate and survival, which then has the potential benefit of making localized treatment more feasible for some cases of oligometastatic cancer. We present a 62-year-old male with stage IVB lung adenocarcinoma with five metastases in the brain. Molecular testing exhibited KRAS and TP53 co-mutation, with negative PD-L1 expression. The patient received six cycles of platinum-based chemotherapy plus pembrolizumab and minimally invasive lobectomy, followed by maintenance therapy with pemetrexed and pembrolizumab. The patient achieved complete disease remission, with no sign of recurrence for 22 months post-treatment. Moreover, we investigated PD-L1 expression and infiltration of immunological cells in biopsy tissue and surgical specimen prior to and after immuno-chemotherapy using multiple immunohistochemistry stains. The different infiltration levels of immune cells for TP53 and KRAS co-mutation were also explored using The Cancer Genome Atlas (TCGA) database and Cell type Identification By Estimating Relative Subsets Of RNA Transcripts (CIBERSORT). To our knowledge, this is the first reported case in which a brain oligometastatic non-small cell lung carcinoma (NSCLC) patient has achieved a complete response after immuno-chemotherapy plus local surgical resection.