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

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 purled 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%), NFI (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.

Automated summary

Analyzing cfDNA in oligometastatic colorectal cancer patients can predict the early recurrence after radiotherapy. The clonality of gene mutations may be associated with patient prognosis, and the presence of cfDNA has a significant correlation with PFS in patients with lung metastases.