Total cell-free DNA measurement in metastatic colorectal cancer with a fast and easy direct fluorescent assay

Abstract

Treatment for metastatic colorectal cancer (mCRC) is focused on prolonging survival and maintaining quality of life. It is important to establish prognostic and predictive markers to avoid extended, ineffective treatment. The aim of the present study was, by a novel approach, to analyze the association between cell-free (cf)DNA levels and outcome in patients receiving systemic therapy for incurable mCRC. The study was a prospective non-interventional biomarker study for patients receiving standard of systemic treatment for mCRC. Patients with mCRC, who, according to standard guidelines, were considered for treatment with EGFR inhibitors, were included. The cfDNA levels in consecutive plasma samples were measured by a direct fluorescence assay. The study included 47 patients. Blood samples were available at baseline (n=47); prior to the third treatment cycle (n=31); the first (n=33), second (n=22) and third response evaluation during treatment (n=17); and at progression (n=22). The disease control rate was 42 and 91% in patients with high (≥75th percentile of baseline cfDNA levels) and low cfDNA levels (<75th percentile of baseline cfDNA levels), respectively (P<0.001). Median progression-free survival (PFS) was 3.8 and 8.5 months in patients with high and low cfDNA levels, respectively (hazard ratio=3.03, 95% CI 1.46-6.29, P<0.01). Median overall survival (OS) was 5.0 and 26.6 months in patients with high and low cfDNA levels, respectively (hazard ratio=3.48, 95% CI 1.44-8.44, P<0.01). In the multivariate analysis, baseline cfDNA levels remained a significant predictor of PFS and OS. In conclusion, cfDNA is a promising prognostic tool in the personalized treatment of mCRC. cfDNA levels were estimated by a simple, rapid and inexpensive method (OPTIPAL II: ClinicalTrials.gov identifier no. NCT03750175; registered November 21, 2018).

Keywords: biomarker; cell-free DNA; colorectal adenocarcinoma; metastatic colorectal cancer; systemic therapy.

Conflict of interest statement

The authors declare that they have no competing interests.

Copyright © 2020, Spandidos Publications.

Figures

Figure 1

Association of baseline plasma cfDNA levels with liver involvement in patients with metastatic colorectal cancer (n=47). Box and whisker plot with 25th, 50th and 75th percentiles, upper and lower adjacent values and outliers (dots) of cfDNA levels. Statistically significant differences are presented as P-values calculated using the Mann-Whitney U-test. cfDNA, cell-free DNA.

Figure 2

Relation between tumor burden according to RECIST version 1.1 (mm) and baseline plasma cfDNA levels (ng/µl) evaluated using a linear regression model for all patients (n=36). cfDNA, cell-free DNA.

Figure 3

Kaplan-Meier curves indicating the association between plasma cfDNA levels (ng/µl) and PFS and OS in 47 patients with metastatic colorectal cancer. Patients were dichotomized according to 75th percentile of cfDNA levels at baseline. Low cfDNA, <75th percentile; high cfDNA, ≥75th percentile. Tick marks indicate censored data. n.r., not reached; CI, confidence interval; cfDNA, cell-free DNA; PFS, progression-free survival; OS, overall survival.

Figure 4

Median plasma cfDNA levels at various time-points: Baseline; just before third treatment cycle; first, second and third response evaluation; and progression in (A) patients with metastatic colorectal cancer (n=47) and (B) a subgroup of patients with liver involvement (n=24). Box and whisker plots with 25, 50 and 75 percentiles, upper and lower adjacent values and outliers (dots) of cfDNA levels. P-values were calculated using the Mann-Whitney U-test. *P<0.01. cfDNA, cell-free DNA.

Figure 5

Relation between tumor burden according to RECIST version 1.1 (mm) and baseline plasma cfDNA levels (ng/µl) evaluated using a linear regression model for patients with liver involvement (n=18). cfDNA, cell-free DNA.

Figure 6

Kaplan-Meier curves indicating the association between plasma cfDNA levels (ng/µl) and PFS and OS in 24 patients with metastatic colorectal cancer with liver involvement. Patients were dichotomized according to 75th percentile of cfDNA levels at baseline. Low cfDNA, <75th percentile; high cfDNA, ≥75th percentile. Tick marks indicate censored data. n.r., not reached; CI, confidence interval; cfDNA, cell-free DNA; PFS, progression-free survival; OS, overall survival.