Early ctDNA stratifies survival in locally advanced and oligometastatic lung cancer treated with radiotherapy
Clinical Cancer Research
Ayesha Hashmi, Jessica Linford, Pradeep S. Chauhan, Kaushal Parikh, Malvika Pillai, John Guittar, Rotem Ben-Shachar, Jyoti Patel, Halla Nimeiri, Matteo Bergsagel, Nicholas P. Semenkovich, Sean S. Park, Kenneth R. Olivier, Dawn Owen, David M. Routman, Katie N. Lee, Alexander D. Sherry, Aaron S. Mansfield, Daniel Morgensztern, Ramaswamy Govindan, Clifford G. Robinson, Carmen Bergom, Saiama N. Waqar, Pamela P. Samson, Bruna Pellini, Gregory R. Vlacich, Aadel A. Chaudhuri
Abstract
Purpose – Circulating tumor fraction estimate (ctFE) is a machine learning-derived composite metric of circulating tumor DNA (ctDNA) burden. We hypothesized that pre-treatment and early on-treatment ctFE could robustly risk-stratify patients with locally advanced (LA) and oligometastatic non-small cell lung cancer (NSCLC) treated with radiotherapy (RT).
Experimental design – In a prospective phase II clinical trial (NCT03916419), 26 patients with unresectable stage IIB to IIIC NSCLC received magnetic resonance (MR)-guided hypofractionated chemoradiotherapy (chemoRT) followed by immunotherapy. Plasma ctDNA was profiled at baseline and mid-treatment (days 10-14) to derive ctFE and maximum variant allele frequency (Max VAF). A burden-based ctFE threshold derived from baseline samples was applied unchanged to mid-treatment samples and validated in two external cohorts: LA NSCLC treated with chemoRT (LA-RW; n = 94) and oligometastatic NSCLC treated with RT (OM-RW; n = 309).
Results – Pre- and mid-treatment ctFE burden strongly stratified overall survival (OS) and progression-free survival (PFS), outperforming Max VAF and ctFE detectability. The baseline ctFE was prognostic for OS (HR 5.93, P = 0.005) and PFS (HR 11.08, P < 0.001) and remained significant at mid-treatment (OS: HR 7.08; PFS: HR 12.06; both P < 0.001). Early ctFE dynamics defined three molecular response groups with OS separation (median OS 60.8 vs. 13.0 vs. 2.9 months; P < 0.001). ctFE remained associated with survival in both validation cohorts.
Conclusions – Early ctFE derived from a clinically available, tumor-naïve ctDNA assay enables noninvasive risk stratification in LA and oligometastatic NSCLC treated with RT, supporting its use as a practical biomarker for precision treatment adaptation.
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