Abstract 3139: Liquid biopsy (ctDNA) testing in clinical management of solid cancers: 5-years of experience
Authors: Benesova Lucie , Belsanova Barbora , Halkova Tereza , Pudil Jiri , Bunganic Bohus , Pesek Milos , Gal Bretislav , Zavoral Miroslav , Ryska Miroslav , Minarik Marek 
Published: July 2016

Abstract
Background: Detection and profiling of circulating tumor DNA (ctDNA) is an attractive tool for management of cancer patients, in particular for early detection of the relapse after surgery or monitoring of response to systemic therapy. The main advantage is minimal invasivity and applicability to a wide range of solid cancers. Methodologies are based on digital PCR with the limit of detection (LOD) below 0.01% mutated alleles, however, these often require significant amounts of input DNA (10s to 100s of ng). In the present work we demonstrate routine detection and clinical utility of ctDNA in a cohort of 423 patients covering a range of 5 different solid tumors.
Methods: ctDNA is detected by somatic mutations found in primary tumor tissue by applying a specific mutation panel targeted to the tumor tape. Detection was done by denaturing capillary electrophoresis (input DNA at concentrations of 5 pg, LOD 0.03 - 1%). The cohort included samples from 257 colorectal cancer patients (CRC), 97 patients with ductal adenocarcinoma of the pancreas (PDAC), 32 patients with non-small cell lung cancer (NSCLC), 12 patients with gastric adenocarcinoma (GA) and 6 patients with head and neck cancers (HNC). A longitudinal monitoring of ctDNA levels prior to surgery, a week after surgery and at three-month follow-up intervals, was performed in 16 CRC patients. Overall ctDNA detection rate, radicality of resection, disease recurrence, tumor dynamics and survival prognosis were evaluated.
Results: ctDNA rates were at 32% for NSCLC, 31% for CRC, 30% for GA, 25% for PDAC and 25% for HNC. When looking at a subgroup of patients in Stage IV of the disease the rates increased to 53% for NSCLC, 77% for CRC, 50% for GA, 46% for PDAC and 50% for HNC. 14 out 16 CRC patients with R0 resection remained ctDNA negative (88%), two patients dropped out of the study. Follow-up monitoring lead to detection of progression in 9 out of 13 patients (69%). In 3 patients (23%), ctDNA positivity preceded standard detection by CT scan. In 5 patients with follow-up exceeding 1 year (5 to 10 sample acquisitions over 15 to 28 month period) the ctDNA levels correlated with the clinical course of the disease (progression/stabilization/remission). There was a borderline statistically significance for prognostic role of ctDNA presence in PDAC patients with 140 days vs. 200 days (P = 0,0519, long-rank test) for ctDNA positive and negative, respectively.
Conclusion: We have introduced a ctDNA method to routine management of 5 different solid cancers. Our results indicate clinical utility for resection radicality confirmation as well as early detection of disease progression and tumor dynamics in CRC patients. The same is applicable to approx. 50% of patients with advanced GA, NSCLC and HNC. CtDNA positivity may also indicate a negative prognosis for PDAC patients. Supported by IGA MZ grant no. NT 13660.
Citation Format: Lucie Benesova, Barbora Belsanova, Tereza Halkova, Jiri Pudil, Bohus Bunganic, Milos Pesek, Bretislav Gal, Miroslav Zavoral, Miroslav Ryska, Marek Minarik. Liquid biopsy (ctDNA) testing in clinical management of solid cancers: 5-years of experience. [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 3139.