BRAF V600E mutations in right-side colon cancer: Heterogeneity detected by liquid biopsy.

INTRODUCTION

The prognosis for metastatic colorectal cancer patients (mCRC) with the BRAF mutation is poor. BRAF mutation frequency is reportedly low among Asians; however, the frequency of the BRAF mutation in right-side colon cancer may not be low, even among Asians. In addition, spatial heterogeneity of BRAF mutations also exists, as for RAS mutations. In this prospective observational study, we evaluated BRAF mutations in cancer tissue and plasma of Japanese right-side colon cancer patients.

METHOD

215 patients with right-side colon cancer were included. BRAF mutations of cancer tissue and plasma were detected using droplet digital PCR. Blood plasma of patients with BRAF mutations in cancer tissue or plasma was drawn at intervals throughout chemotherapy, and BRAF mutations were evaluated.

RESULTS

BRAF mutations were detected in tissue samples from 35 of 215 patients (16.3%, cecum; 22.4%, ascending colon; 17.8%, and transverse colon; 9.0%). BRAF mutations were detected in plasma of 10 of 215 (4.7%) patients. Eight of the ten patients had BRAF mutations in their primary tumours, but two (both were Stage IV) patients did not. Sensitivity of liquid biopsy to detect BRAF mutations was 10.3% (3/29) in Stage I-III patients and 83.3% (5/6) in Stage IV patients.

CONCLUSION

BRAF mutations are observed in right-side colon cancer at high frequency, especially in the cecum. BRAF mutations can be detected in plasma and the detection rate is high in patients with advanced cancer. Spatial heterogeneity was observed using liquid biopsy.