Abstract 3134: Prediction of early recurrence after resection of metastatic liver tumors from colorectal cancer using circulating cell-free DNA
Authors: Iwai Takuma , Yamada Takeshi , Kan Hayato , Koizumi Michihiro , Shinji Seiichi , Yokoyama Yasuyuki , Takahashi Goro , Kitano Shiro , Nakayama Masato , Naito Zenya , Ohta Keiichiro , Uchida Eiji 
Published: July 2016

Abstract
Background: We have reported that the amount of total circulating cell-free DNA (ccfDNA) increases with tumor growth and decreases upon tumor shrinkage. However, adverse effects of drugs and surgical stress can increase total ccfDNA because ccfDNA is derived from both normal and cancer cells. Thus, the ability to determine how much ccfDNA is derived from cancer cells is a critical issue. It has been reported that the length of ccfDNA derived from cancer cells is greater than 200 bp while that from normal cells undergoing apoptosis is less than 200 bp. Furthermore, the ratio of ccfDNA to β-globin reflects the amount of mitochondrial DNA derived from normal cells undergoing stress-induced apoptosis. We developed a new biomarker readout, the LINE-1 long fragment (longer than 200 bp) to β-globin ratio (LBR), based on this principle. In this study, we evaluated the clinical utility of the LBR to detect early recurrence of liver metastasis from colorectal cancer after liver resection.
Methods: We enrolled 20 patients who underwent curative liver resection of metastatic liver tumors from colorectal cancer. Total ccfDNA and LBR were measured pre-surgery, and at 1 week and 1 month post-surgery. ccfDNA was purified from 1 mL serum using the QIAamp Circulating Nucleic Acid Kit. Total ccfDNA was measured using Qubit Fluorometer. LINE-1 long fragment and β-globin in ccfDNA were measured using real time PCR. The Ethics Review Committee of our institution approved the study protocol. Written informed consent was obtained from each patient.
Results: We completed 1-year follow-up in 13 of 20 patients. Recurrence was detected in 7 patients and no signs of recurrence were detected in the other 6. Total ccfDNA increased 1 week after surgery in all 13 patients, which could have been caused by surgical stress. Total ccfDNA 1 month after surgery increased in 5 of 7 patients with recurrence. Total ccfDNA 1 month after surgery increased in 3 of 6 patients without recurrence. The 3 patients with increased ccfDNA had post-operative complications or drug-induced liver dysfunction. Notably, LBR increased in the 7 patients with recurrence and decreased in the 6 patients without recurrence 1 month post-surgery.
Conclusion: LBR has potential as a novel biomarker readout for early detection of recurrence after liver resection of metastatic liver tumors from colorectal cancer.
Citation Format: Takuma Iwai, Takeshi Yamada, Hayato Kan, Michihiro Koizumi, Seiichi Shinji, Yasuyuki Yokoyama, Goro Takahashi, Shiro Kitano, Masato Nakayama, Zenya Naito, Keiichiro Ohta, Eiji Uchida. Prediction of early recurrence after resection of metastatic liver tumors from colorectal cancer using circulating cell-free DNA. [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 3134.