151. Clinical Significance of BRAF Non-V600E Mutations in Colorectal Cancer: A Retrospective Study of Two Institutions
- Author
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Hiroshi Ichikawa, Masayuki Nagahashi, Shujiro Okuda, Yoshifumi Shimada, Hidehito Oyanagi, Yosuke Tajima, Kazuaki Takabe, and Toshifumi Wakai
- Subjects
0301 basic medicine ,Oncology ,Adult ,Male ,Proto-Oncogene Proteins B-raf ,Vascular Endothelial Growth Factor A ,medicine.medical_specialty ,Colorectal cancer ,Disease ,medicine.disease_cause ,03 medical and health sciences ,0302 clinical medicine ,Internal medicine ,Medicine ,Humans ,Clinical significance ,Egfr signaling ,Aged ,Retrospective Studies ,Aged, 80 and over ,Mutation ,business.industry ,Retrospective cohort study ,Middle Aged ,medicine.disease ,ErbB Receptors ,030104 developmental biology ,030220 oncology & carcinogenesis ,Surgery ,Female ,business ,Colorectal Neoplasms ,Progressive disease ,V600E - Abstract
Background Recent advances in next-generation sequencing have enabled the detection of BRAF V600E mutations as well as BRAF non-V600E mutations in a single assay. The present work aimed to describe the clinicopathological characteristics and clinical outcome of the BRAF non-V600E mutant-type in colorectal cancer (CRC). Patients and methods CRC samples from 111 Stage IV patients were analyzed for somatic mutations using a 415-gene comprehensive genomic sequencing panel. Patients were classified according to BRAF status as wild-type, V600E mutant-type, or non-V600E mutant-type. Differences between clinicopathological characteristics and genetic alterations were analyzed among the three groups. Overall survival (OS) and the response to anti-EGFR therapy were also analyzed. Results Comprehensive genomic sequencing revealed that 98 patients (88%), 7 patients (6%), and 6 patients (6%) were wild-type, V600E mutant-type, and non-V600E mutant-type, respectively. Non-V600E mutant-type tumors were frequently left-sided (83%), while V600E mutant-type tumors were frequently right-sided (86%; P = 0.025). Non-V600E mutant-type showed better OS than V600E mutant-type (P = 0.038), with no significant difference compared with wild-type tumors. The two patients with non-V600E mutations who underwent repeated metastasectomies showed no evidence of disease at final follow-up. Regarding the efficacy of anti-EGFR therapy, the patient with an I326V mutation had progressive disease (+115%) despite no genetic alterations detected in the EGFR pathway that could drive resistance, suggesting an alternate resistance mechanism. Conclusions Non-V600E mutant-type is more likely to be left-sided and demonstrates better OS than V600E mutant-type. Further preclinical and clinical investigations are needed to clarify the role of non-V600E mutations in CRC.
- Published
- 2018