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Clin Cancer Res. 2018 Apr 15;24(8):1872-1880. doi: 10.1158/1078-0432.CCR-17-1341. Epub 2018 Jan 12.

Early Assessment of Lung Cancer Immunotherapy Response via Circulating Tumor DNA.

Author information

1
Department of Medicine (Medical Oncology), Yale School of Medicine, Yale University, New Haven, Connecticut.
2
Department of Therapeutic Radiology, Yale School of Medicine, Yale University, New Haven, Connecticut.
3
Simons Foundation, New York, New York.
4
Department of Genetics, Yale School of Medicine, Yale University, New Haven, Connecticut.
5
Yale Center for Analytical Sciences, Yale School of Public Health, New Haven, Connecticut.
6
Department of Biostatistics, Yale School of Public Health, New Haven, Connecticut.
7
Department of Thoracic Surgery, Yale School of Medicine, Yale University, New Haven, Connecticut.
8
Department of Pathology, Yale School of Medicine, Yale University, New Haven, Connecticut.
9
Department of Therapeutic Radiology, Yale School of Medicine, Yale University, New Haven, Connecticut. abhijit.patel@yale.edu.
#
Contributed equally

Abstract

Purpose: Decisions to continue or suspend therapy with immune checkpoint inhibitors are commonly guided by tumor dynamics seen on serial imaging. However, immunotherapy responses are uniquely challenging to interpret because tumors often shrink slowly or can appear transiently enlarged due to inflammation. We hypothesized that monitoring tumor cell death in real time by quantifying changes in circulating tumor DNA (ctDNA) levels could enable early assessment of immunotherapy efficacy.Experimental Design: We compared longitudinal changes in ctDNA levels with changes in radiographic tumor size and with survival outcomes in 28 patients with metastatic non-small cell lung cancer (NSCLC) receiving immune checkpoint inhibitor therapy. CtDNA was quantified by determining the allele fraction of cancer-associated somatic mutations in plasma using a multigene next-generation sequencing assay. We defined a ctDNA response as a >50% decrease in mutant allele fraction from baseline, with a second confirmatory measurement.Results: Strong agreement was observed between ctDNA response and radiographic response (Cohen's kappa, 0.753). Median time to initial response among patients who achieved responses in both categories was 24.5 days by ctDNA versus 72.5 days by imaging. Time on treatment was significantly longer for ctDNA responders versus nonresponders (median, 205.5 vs. 69 days; P < 0.001). A ctDNA response was associated with superior progression-free survival [hazard ratio (HR), 0.29; 95% CI, 0.09-0.89; P = 0.03], and superior overall survival (HR, 0.17; 95% CI, 0.05-0.62; P = 0.007).Conclusions: A drop in ctDNA level is an early marker of therapeutic efficacy and predicts prolonged survival in patients treated with immune checkpoint inhibitors for NSCLC. Clin Cancer Res; 24(8); 1872-80. ©2018 AACR.

PMID:
29330207
PMCID:
PMC5899677
[Available on 2019-04-15]
DOI:
10.1158/1078-0432.CCR-17-1341

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