Prospective, Cell-Free Circulating Tumor DNA (ctDNA) Profiling in Locally Advanced Lung Cancer Treated with Chemoradiation

PURPOSE/OBJECTIVE(S)

Liquid biopsy for cell-free circulating tumor DNA (ctDNA) allows for non-invasive, comprehensive genomic profiling. We explored the utility prospective liquid biopsy for (ctDNA) in among non-small cell lung cancer (NSCLC) patients treated with definitive chemoradiation.

MATERIALS/METHODS

This prospective clinical cohort consists of unresectable, locally advanced NSCLC patients who had liquid biopsy testing prior to initiation of cancer therapy. Liquid biopsy testing was performed using a next-generation sequencing assay (MSK-ACCESS) which includes 129 genes and paired white blood cell sequencing. An FDA-recognized database (OncoKB) was utilized to classify alterations associated with radiation resistance (including KEAP1, NFE2L2, STK11, and PIK3CA) and radiation sensitivity (including ATM, ATR, BRCA1/2, ARID1A, MLH1 and other DNA Damage Repair Pathway alterations). We evaluated progression-free survival (PFS) from the completion of chemoradiation using the Log-rank test.

RESULTS

Among 25 patients with prospective ctDNA testing prior to therapy initiation, 17 patients had stage III disease (68%), 8 patients had stage II disease (32%), 18 patients had adenocarcinoma (72%), 7 patients had squamous cell carcinoma (28%), and 23 (92%) were former or current smokers. The median radiation dose was 60 Gy in 30 fractions (range: 55 to 66 Gy in 20 to 33 fractions). 76% of patients (n = 18) had one or more alterations detected (median: 3 alterations, range: 1 - 8) including genomic markers of radiation response in 2 patients in BRCA1/2 (n = 2) and radiation resistance in 1 patient in KEAP1. The most common driver alteration detected was KRAS in 24% of the cohort (n = 6). Among patients with baseline detectable ctDNA, the median PFS was 21.3 months and was not reached among patients without baseline ctDNA detection (HR 4.54, p = 0.04).

CONCLUSION

Using an institutional assay, the presence of baseline cell-free ctDNA appeared prognostic in patients with unresectable, locally advanced NSCLC treated with definitive chemoradiation. We also detected driver alterations and potential markers of radiation resistance and response using ctDNA testing. Prospective cell-free ctDNA profiling may offer pathways to therapy personalization among patients with locally advanced unresectable lung cancer.

ctDNA-based detection of molecular residual disease in stage I-III non-small cell lung cancer patients treated with definitive radiotherapy

Background

Sensitive and reliable biomarkers for early detection of recurrence are needed to improve post-definitive radiation risk stratification, disease management, and outcomes for patients with unresectable early-stage or locally advanced non-small cell lung cancer (NSCLC) who are treated with definitive radiation therapy (RT). This prospective, multistate single-center, cohort study investigated the association of circulating tumor DNA (ctDNA) status with recurrence in patients with unresectable stage I-III NSCLC who underwent definitive RT.

Methods

A total of 70 serial plasma samples from 17 NSCLC patients were collected before, during, and after treatment. A personalized, tumor-informed ctDNA assay was used to track a set of up to 16 somatic, single nucleotide variants in the associated patient's plasma samples.

Results

Pre-treatment ctDNA detection rate was 82% (14/17) and varied based on histology and stage. ctDNA was detected in 35% (6/17) of patients at the first post-RT timepoint (median of 1.66 months following the completion of RT), all of whom subsequently developed clinical progression. At this first post-RT time point, patients with ctDNA-positivity had significantly worse progression-free survival (PFS) [hazard ratio (HR): 24.2, p=0.004], and ctDNA-positivity was the only significant prognostic factor associated with PFS (HR: 13.4, p=0.02) in a multivariate analysis. All patients who developed clinical recurrence had detectable ctDNA with an average lead time over radiographic progression of 5.4 months, and post-RT ctDNA positivity was significantly associated with poor PFS (p<0.0001).

Conclusion

Personalized, longitudinal ctDNA monitoring can detect recurrence early in patients with unresectable NSCLC patients undergoing curative radiation and potentially risk-stratify patients who might benefit most from treatment intensification.