講演情報
[P3-1-4]抗EGFR薬投与中の結腸直腸癌患者におけるctDNAのHER2増幅と治療抵抗性に関する検討
香中 伸太郎, 山田 岳史, 上原 圭, 進士 誠一, 松田 明久, 横山 康行, 高橋 吾郎, 岩井 拓磨, 宮坂 俊光, 吉田 寛 (日本医科大学付属病院消化器外科)
Background：Although the proportion of overamplified the human epidermal growth factor receptor 2 gene ERBB2（HER2）in colorectal cancer is not high（2-3％）, it is an important factor in the resistance to anti-EGFR therapy as well as therapeutic targets. Methods： We retrospectively collected and analyzed data of patients who underwent anti-EGFR therapy for metastatic or recurrence CRC from January 2014 to December 2020 at our department. The patients were divided into two groups：those who were responders for anti-EGFR therapy（RS-group, n=55）and those non-responders（NRS-group, n=67）. Results： There was a significant increase in HER2 amplification in the NRS group compared to the RS group（RS group：P=0.23, NRS group：P=0.02, respectively）. The post/pre HER2 ratio was significantly higher in the NRS group than in the RS group（0.97±0.35 vs. 1.37±1.52, P=0.04）. When the threshold was set at 1.77, the specificity of resistant for anti-EGFR therapy was 100％, and all cases with a post/pre HER2 ratio greater than 1.77 were non-responders. Conclusion： The non-responders for anti-EGFR therapy had significantly increased HER2 amplification. Particularly, the patients with a high post/pre-HER2 ratio（cut-off=1.77 in the present experiment）might be associated with resistance to anti-EGFR therapy due to HER2 amplification.