Circulating Tumor DNA Analysis for Patients with Oncogene-Addicted NSCLC With Isolated Central Nervous System Progression

Introduction: In patients with oncogene-addicted NSCLC and isolated central nervous system progression (iCNS), tissue biopsy is challenging, and the clinical utility of plasma liquid biopsy (i.e., circulating tumor DNA [ctDNA]) is unknown.

Methods: Patients with advanced NSCLC with known baseline genomic alteration (GA) (EGFR, ALK, BRAF, KRAS, HER2, ROS1, MET, PIK3CA, STK11, TP53) on tissue were divided into three groups on the basis of their disease progression pattern: iCNS, extra-CNS only (noCNS), or both (cCNS). All patients with available plasma ctDNA were included and were analyzed by next-generation sequencing InVisionFirst-Lung. ctDNA was considered positive if at least one GA was detected. Cell-free tumor DNA was analyzed in cerebrospinal fluid when available.

Results: Out of 517 patients screened, 247 were included: 54 had iCNS, 99 had noCNS, and 94 had cCNS progressive disease (64, 128, and 110 ctDNA samples, respectively). CtDNA was positive in 52% iCNS versus 84% in noCNS and 92% in cCNS (p < 0.00001), with lower detection of driver (37% versus 77% and 73%, respectively) and resistance alterations (6% versus 45% and 44%). Patients with iCNS and positive ctDNA were more at risk of extra-CNS progression (32% versus 7%, p = 0.026). In 12 patients with iCNS, ctDNA was positive in six (50%) plasma and in 10 (83%) paired cerebrospinal fluid (p = 0.193).

Conclusions: Although tagged amplicon-based next-generation sequencing has high detection rates of GA in plasma ctDNA in patients with NSCLC with extra-CNS disease, detection rate of GAs (52%) is lower in the subset of patients with iCNS disease. Complementary tests such as cerebrospinal fluid cell-free DNA may be useful. Further evidence would be beneficial to understand the genomic landscape in patients with NSCLC and iCNS.