Liquid Biopsy Cell-free DNA Biomarkers in Patients With Oligometastatic Colorectal Cancer Treated by Ablative Radiotherapy.

ABSTRACT

BACKGROUND/AIM: To investigate the usefulness of cell-free DNA (cfDNA) in patients with oligometastasis. PATIENTS AND METHODS: This study included oligometastatic colorectal cancer (CRC) patients who underwent ablative irradiation using stereotactic body radiotherapy or proton beam therapy for metastatic lesions at a single institution. cfDNA was purified from the plasma of pretreated patients and gene mutations were analyzed by next-generation sequencing. Progression-free survival (PFS) was statistically compared according to gene mutation, clonality or allele frequency. RESULTS: A total of 20 patients were analyzed. Mutations were detected in the following genes; TP53 (45%), APC (40%), KRAS (15%), PIK3CA (15%), NF1 (5%), BRCA1 (5%), ERBB2 (5%), FBXW7 (5%), KIT (10%), and HRAS (10%). Patients with multi-clonality of gene mutation showed tendency for poor PFS (p=0.07). Among 7 patients whose metastatic site was the lung, those with no cfDNA detected had significantly better PFS than those with cfDNA (p=0.02). CONCLUSION: cfDNA profiles could be predictive tools for early recurrence of oligometastatic CRC patients after ablative radiotherapy.