Molecular-based targeted therapies have significantly benefited certain patients with cancer; however, those with leptomeningeal disease (LMD) persistently exhibit a poor prognosis and are often excluded from clinical trials. Tumor-derived cell-free (cf)DNA, found in the cerebrospinal fluid (CSF) of patients with LMD, can assist in diagnosis and tracking of disease progression. However, the utilization of CSF to direct targeted cancer therapy has yet to be extensively explored. The present study reported the case of a patient with lung adenocarcinoma and LMD who was monitored by performing a series of liquid biopsies of CSF and blood. Targeted sequencing was performed on cfDNA from the CSF and plasma, and the variant allele frequencies (VAFs) of BRAF and NRAS mutations were assessed and analyzed in conjunction with the clinical presentation of the patient. The patient then underwent serial chemotherapy, radiation therapy, immunotherapy and targeted treatment based on the results of the liquid biopsies. Upon the LMD diagnosis, a BRAF p.V600E mutation was detected in plasma cfDNA. Consequently, the patient was treated with vemurafenib and responded favorably to this consolidation treatment for 13 months. After a relapse in July 2018, both BRAF p.V600E and NRAS p.Q61K mutations were detected in CSF supernatant and sediment cell samples, suggesting drug resistance. Therefore, the treatment strategy for the patient changed to cobimetnib plus vemurafenib. Notably, the changes of VAF in the CSF supernatant samples were associated with the clinical status of the patient. The patient survived for 33 months post-LMD diagnosis. The present case report highlights the potential use of liquid biopsy in personalized therapy, as it was instrumental in informing the combinational treatment plan of the patient, which ultimately proved beneficial.
Keywords: BRAF V600E; NRAS Q61K; cerebrospinal fluid; circulating tumor DNA; drug resistance; leptomeningeal disease.
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