Immune and Circulating Tumor DNA Profiling After Radiation Treatment for Oligometastatic Non-Small Cell Lung Cancer: Translational Correlatives from a Mature Randomized Phase II Trial

Abstract

Purpose: NCT01725165 was a phase II prospective trial in which patients with non-small cell lung cancer were randomized to local consolidative therapy (LCT) versus maintenance therapy or observation (MT/O).

Methods and materials: Peripheral blood from patients enrolled on NCT01725165 were labeled as (1) baseline, (2) early follow-up (FU) if obtained in the first or second FU evaluation (6-18 weeks), and (3) late FU if obtained in the third to sixth FU evaluations (22-50 weeks). All patients who underwent LCT and were included in this analysis received radiation. Among 49 randomized patients, 21 patients underwent T cell CDR3 variable region sequencing using immunoSEQ, 31 patients underwent circulating tumor DNA (ctDNA) analysis using next-generation sequencing with a 1021 cancer gene panel, and cytokine concentration was assayed in 19 patients using enzyme-linked immunosorbent assay. All analyses were exploratory and not corrected for multiple testing.

Results: No associations were identified between baseline T cell repertoire and ctDNA metrics with patient outcomes. Among baseline cytokines, interleukin 1α was the only cytokine associated with both overall survival (hazard ratio, 0.02; 95% confidence interval, 0.1-0.5; P = .0006) and progression-free survival (hazard ratio, 0.5; 95% confidence interval, 0.2-0.9; P = .03). At early FU, LCT was associated with decreased ctDNA burden, including lower number of detected mutations (median, 2 [interquartile range {IQR}, 1-6] vs 6 [IQR, 4-18]) and decreased average variable allele frequency (VAF; median, 0.006 [IQR, 0.003-0.010] vs 0.011 [IQR, 0.007-0.014]) compared with MT/O. Among 6 patients with serial ctDNA analysis, a rise in ctDNA detected mutation burden preceded clinical progression by 6.7 months. At early FU, LCT was associated with changes in T cell clonality that suggested oligoclonal expansion specifically increased T cell clonality (median, 0.15 [IQR, 0.12-0.24] vs 0.10 [IQR, 0.05-0.13]) and frequency of top 10 clones (median, 0.14 [IQR, 0.06-0.18] vs 0.21[IQR, 0.19-0.28]).

Conclusion: LCT was associated with decreased ctDNA burden and oligoclonal expansion at early FU timepoints. Baseline interleukin 1α was associated with improved patient outcomes.