Abstract 563: Identification of a novel biomarker to predict pathologic complete response for neoadjuvant chemoradiotherapy in locally advanced rectal cancer

Abstract

Abstract Neoadjuvant chemoradiotherapy (CRT) followed by total mesorectal excision (TME) is the standard treatment for locally advanced rectal cancer (LARC). Good pathologic response to CRT is associated with better outcome. However, there is a lack of effective methods to select rectal cancer patients who would or would not have a benefit from CRT. Therefore, we aimed to perform whole-exome sequencing (WES) for rectal cancer to identify the novel genetic variations predicting CRT benefit in LARC. Two independent sets were used to evaluate the genetic differences between the good response group and poor response group to CRT. Fifteen patients who achieved pathologic complete response were divided into the good response group and 15 patients with pathologic stage III were classified as poor response group. Among these 30 patients, WES was examined. To validate discovery set, additional samples (n=67) were genotyped for candidate variants using TaqMan SNP genotyping assays or Sanger sequencing. Overall, the current study included a total of 97 LARC patients who were treated with neoadjuvant CRT followed by curative surgery at Kyungpook National University Medical Center. We found 5 candidate variants significantly associated with pathologic complete response (BCL2L10 rs2231292, DLC1 rs3816748, DNAH14 rs3105571, ITIH5 rs3824658, RAET1L rs912565) using WES. In the dominant model, patients with GC/CC genotype of DLC1 rs3816748 (p=0.032), AC/CC genotype of DNAH14 rs3105571 (p=0.009) and TT genotype of RAET1 rs912565 (p<0.0001) showed higher rate of pCR compared to those of other genotype patients. In the recessive model, the BCL2L10 rs2231292 (p=0.036) and ITIH5 rs3824658 (p=0.003) were significantly associated with pathologic CR. Four SNPs (DLC1 rs3816748, DNAH14 rs3105571, ITIH5 rs3824658, RAET1L rs912565) found to be significantly correlated with pCR in codominant model. However, none of the SNPs was associated with the relapse-free survival or overall survival. The present results suggest that the genetic variation of the BCL2L10 rs2231292, DLC1 rs3816748, DNAH14 rs3105571, ITIH5 rs3824658, and RAET1L rs912565 genes can be used as biomarkers predicting CRT response for patients with LARC. Citation Format: Jong Gwang Kim, In Hee Lee, Soo Jung Lee, Yee Soo Chae, Byung Woog Kang. Identification of a novel biomarker to predict pathologic complete response for neoadjuvant chemoradiotherapy in locally advanced rectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 563.