Prospective Feasibility Study for Using Cell-Free Circulating Tumor DNA–Guided Therapy in Refractory Metastatic Solid Cancers: An Interim Analysis

Abstract

PurposeRetrospective studies have demonstrated that cell-free circulating tumor DNA (ctDNA) hotspot testing predicts matched therapy response to first- and second-line therapies in patients with advanced non–small-cell lung cancer (NSCLC). However, no prospective outcomes studies have evaluated ctDNA-guided matched therapy decision making on the basis of comprehensive plasma genomic testing including all four major classes of alterations. Here, we report the clinical utility of this approach in advanced solid tumor cancers.Patients and MethodsWe conducted a multiple parallel cohort, open-label, clinical trial using ctDNA-guided matched therapy when tissue was insufficient or unobtainable for next-generation sequencing. Plasma-based digital sequencing identified point mutations in 70 genes and indels, fusions, and copy number amplifications in selected genes. Patients with prespecified targetable alterations in metastatic NSCLC, gastric cancer (GC), and other cancers were matched to several independent targeted agent trials at a tertiary academic center.ResultsSomatic alterations were detected in 59 patients with GC (78%), and 25 patients (33%) had targetable alterations (ERBB2, n = 11; MET, n = 5; FGFR2, n = 3; PIK3CA, n = 6). In NSCLC, 62 patients (85%) had somatic alterations, and 34 (47%) had targetable alterations (EGFR, n = 29; ALK, n = 2; RET, n = 1; ERBB2, n = 2). After confirmation of ctDNA findings on tissue (to meet trial eligibility criteria), 10 patients with GC and 17 patients with NSCLC received molecularly matched therapy. Response rate and disease control rate were 67% and 100%, respectively, in GC and 87% and 100%, respectively, in NSCLC. Response was independent of targeted alteration variant allele fraction in NSCLC (P = .63).ConclusionTo our knowledge, this is the first prospective feasibility study of comprehensive ctDNA-guided treatment in advanced GC and lung cancers. Response rates in this interim analysis are similar to those in tissue-based targeted therapy studies.