Abstract 90P
Background
There is a correlation of genomic alterations between tumor tissue and circulating cell-free DNA (cfDNA) in blood samples, mostly in advanced stages of cancer. The main objective of this study was the characterization of cfDNA of patients with non-small cell lung cancer (NSCLC) stages I–III before the adjuvant treatment (at the time of surgical intervention) and in those who relapse, with next generation sequencing (NGS). It was expected that the results could determine the changes that occur in cfDNA during treatment, follow-up and relapse.
Methods
Two blood samples were collected from each patient (before surgery and at relapse) and a paraffin tissue sample from the surgical specimen. cfDNA from blood plasma was sequenced using the 50-gene Oncomine Pancancer Assay panel. DNA obtained from tissues was analyzed with the 50-gene Oncomine Focus Assay panel.
Results
This prospective study included 73 patients with NSCLC of whom 22 met inclusion criteria (adjuvant treatment after surgery). The mean age was 63.36 years with a male/female ratio of 2.44. The concentrations of cfDNA were 1.42 ± 0.55, 1.57 ± 1.58 and 1.03 ± 0.45 ng/µl for stages I, II and III respectively with no significant differences. To date, two of the 22 patients have relapsed. The mean ratio of the cfDNA concentration (time of relapse/time of surgery) was 2.96. In the patient 1, no genetic variants were found in the three samples analyzed. The first liquid biopsy of patient 2 carried the p.R249S mutation in the TP53 gene and a 1.5-fold increase in CCND2 gene dosage. At the time of relapse, the allelic frequency of p.R249S alteration augmented from 3 to 40% and a 2.5-fold increase in CCND2 gene dosage was observed.
Conclusions
The use of liquid biopsy in early stages and the follow-up of patients with NSCLC is a potential tool for detecting tumor recurrence, as demonstrated by the increase in cfDNA concentration, mutated allele frequency and gene dosage after relapse. A long-term follow-up is required to assess the consistency and robustness of results.
Legal entity responsible for the study
Hospital Universitario Cruces- Biocruces Bizcaia Health Research Institute.
Funding
EITB Maratoia (BIO19/CP/003).
Disclosure
All authors have declared no conflicts of interest.