Circulating Tumor DNA Dynamics as Prognostic Markers in Locally Advanced and Metastatic Esophageal Squamous Cell Carcinoma

Abstract

Importance: Esophageal squamous cell carcinoma (ESCC) is a deadly disease with frequent recurrence. There are unmet needs for prognostic biomarkers for dynamically monitoring disease progression and detecting minimal residual disease.

Objective: To examine whether circulating tumor DNA is clinically useful as a prognostic biomarker for ESCC recurrence and patient survival.

Design, setting, and participants: This single-center, population-based cohort study consecutively enrolled 147 patients receiving curative (n = 74) or palliative (n = 73) treatment at the surgery and clinical oncology departments of Queen Mary Hospital in Hong Kong from August 1, 2016, to September 31, 2021. Patients were followed up for 2 years. Plasma samples were collected at different longitudinal time points for a prospective circulating tumor DNA (ctDNA) next-generation sequencing profiling study of 77 actionable genes.

Intervention: Patients were treated with up-front surgery, neoadjuvant chemoradiotherapy plus surgery with or without adjuvant therapy, or palliative chemotherapy (CT).

Main outcomes and measures: Detection of circulating tumor DNA (ctDNA), progression-free survival (PFS), and overall survival (OS).

Results: A total of 478 serial plasma samples from 147 patients with locoregional or metastatic ESCC were prospectively analyzed. Among the 74 patients in the curative group (median [range] age, 66 [46-85] years; 56 [76.0%] male), 44 (59.5%) relapsed and 36 (48.6%) died. For patients receiving curative surgical treatment, a high ctDNA level (hazard ratio [HR], 7.84; 95% CI, 1.87-32.97; P = .005) and ctDNA alterations (HR, 5.71; 95% CI, 1.81-17.97; P = .003) at 6 months postoperation were independently associated with poor OS. Among patients receiving neoadjuvant chemoradiotherapy, postneoadjuvant ctDNA alterations were associated with poor PFS (HR, 3.16; 95% CI, 1.17-8.52; P = .02). In the 73 patients in the palliative group (median [range] age, 63 [45-82] years; 63 [86.0%] male), 71 (97.3%) had disease relapse and 68 (93.2%) died. Detectable pre-CT NFE2L2 alterations were independently associated with PFS (HR, 2.99; 95% CI, 1.35-6.61; P = .007) and OS (HR, 28.39; 95% CI, 7.26-111.03; P = 1.52 × 10-6), whereas high ctDNA levels (HR, 2.41; 95% CI, 1.18-4.95; P = .02) and alterations in pre-cycle III ctDNA (HR, 1.99; 95% CI, 1.03-3.85; P = .04) showed weaker associations with PFS. Alterations in pre-CT ctDNA were independently associated with OS (HR, 4.46; 95% CI, 1.86-10.69; P = 7.97 × 10-4).

Conclusions and relevance: The findings of this cohort study indicate that prognostic models incorporating ctDNA features are useful in ESCC. Both ctDNA level and NFE2L2 alterations pre-CT and before cycle III were found to be important prognostic factors in palliative groups, and ctDNA alterations after treatment and at 6 months after surgery may define high-risk groups for recurrence in the curative group. High-risk patients can benefit by a timely switch to the next therapeutic options.

Figure 1.. Genetic Profile of Circulating Tumor (ctDNA) in Patients With Esophageal Squamous Cell Carcinoma (ESCC)

The ctDNA genotyping results and clinical characteristics are shown for all patients with ESCC (n = 123). Each column represents a patient, and each row represents a gene or clinical parameter. The bar chart on the upper panel indicates the number of alterations in each patient, and the chart on the right indicates the number of patients harboring alterations in that gene. Pink dots represent alterations in hotspots identified in the public database. The top 30 most frequently altered genes are depicted.

Figure 2.. Longitudinal Circulating Tumor DNA Analysis for Relapse Detection and Disease Monitoring

The serial change in minor allele frequency during the clinical course was compared with the imaging results in the curative group (n = 33) and the palliative group (n = 46). Circles indicate the change in alterations at different time points, and arrows represent the imaging results.

Figure 3.. Change in Circulating Tumor DNA (ctDNA) Minor Allele Frequency (MAF) Preceding Disease Relapse Detected by Imaging

Comparison of the recurrence time measured by imaging vs ctDNA in the curative group (P < .001) and the palliative group (P < .001) by Wilcoxon paired signed rank test. Longitudinal dynamic change in MAF was highly associated with and preceded the conventional imaging in detecting disease. PD indicates progressive disease; PET, positron emission tomography; PR, partial response.

Figure 4.. Prognostic Ability of Circulating Tumor DNA (ctDNA) Level and Genetic Alterations in the Curative and Palliative Groups

For the curative group, patients with more than 1 alteration in ctDNA at 6 months postoperatively (n = 38) had an increased risk for progression-free survival (PFS) and overall survival (OS). For the palliative group, patients with NFE2L2 alterations in prechemotherapy ctDNA (n = 70) had an increased risk for PFS and OS. P values were adjusted from multiple testing correction. HR indicates hazard ratio; WT, wild type.