Abstract 510: A novel circulating cell free DNA-based assay in colorectal cancer patients during treatment with systematic chemotherapy
Authors: Toshima Toshiaki , Nagasaka Takeshi , Mori Yoshiko , Kawai Takashi , Fuji Tomokazu , Taniguchi Fumitaka , Kimura Keisuke , Yasui Kazuya , Kishimoto Hiroyuki , Umeda Yuzo , Tazawa Hiroshi , Goel Ajay , Fujiwara Toshiyoshi 
Published: July 2016

Introduction: Although circulating cell-free DNA (cfDNA) in blood plasma is being touted as a frontier noninvasive approaches, its clinical utility still remains questionable. The purpose of this study was to compare the efficacy of cfDNA by comparing blood CEA levels and radiological evaluation in patients with unresectable metastatic colorectal cancer (mCRC) who received systemic chemotherapy.

Experimental Procedures: In this study, we measured aberrant cancer-specific methylation in cfDNA and the concentration of cfDNA in plasma obtained following each treatment cycle of systemic chemotherapy in three patients with mCRC. To analyze aberrant cancer-specific methylation, we used a modified highly sensitive assay for bisulfite DNA followed by fluorescence-based PCR, as reported previously (JNCI 2009). This methodology can detect methylation status in eight regions, therefore both recovery score (RS) and methylation score (MS), ranged from 0-8 at a given time. We measured RS and MS two-times in each plasma specimen obtained before administration of systemic chemotherapies.

Results: In this pilot study, we examined a series of blood plasma obtained from three patients who received oxaliplatin-based chemotherapy together with molecularly-targeted agents. Despite initial tumor shrinkage in the metastases, all patients ultimately developed progressive disease (PD). Patient1 had wild-type KRAS, but had developed a sigmoid colon cancer with synchronous multiple liver and lung metastases. In contrast, Patient2 had mutant KRAS with sigmoid colon cancer and synchronous multiple liver metastasis. Both patients 1 and 2, demonstrated decreasing levels of CEA after the first-line chemotherapy, along with low methylation scores and concentration of cfDNA. Interestingly, in both patients, MS and concentration level of cfDNA increased prior to radiographic documentation of PD. Patient3 harbored BRAF V600E mutation, and a cancer in the ascending colon with systemic lymph node metastasis. Although, in this case, the tumor development progressed rapidly, similar to patients 1 and 2, MS and the concentration levels of cfDNA also increased prior to radiographic documentation of rapid PD.

Conclusions: Our novel DNA methylation and concentration-based monitoring assay is a novel methodology for capturing DNA methylation in circulating cell-free DNA in plasma, and is useful for the early identification of colorectal cancer patients who are at risk of developing PD prior to radiographic documentation.

Citation Format: Toshiaki Toshima, Takeshi Nagasaka, Yoshiko Mori, Takashi Kawai, Tomokazu Fuji, Fumitaka Taniguchi, Keisuke Kimura, Kazuya Yasui, Hiroyuki Kishimoto, Yuzo Umeda, Hiroshi Tazawa, Ajay Goel, Toshiyoshi Fujiwara. A novel circulating cell free DNA-based assay in colorectal cancer patients during treatment with systematic chemotherapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 510.