Abstract P2-02-21: Longitudinal analysis of circulating tumor cells and cell free tumor DNA by next generation sequencing in triple negative breast cancer
Authors: Howard K , Austin S , Ramirez AB , Ritter L , Boles D , Pruitt J , Collins H , Mahen E , Leonti A , Maassel L , Subia C , Tuuli S , Heying N , Deutsch K , Cox J , Lo FY , Stilwell JL , Kaldjian EP , Dorschner M , Blau S , Blau A , Eisenberg M , Anderson S , Madan A 
Published: May 2016

As the practice of genetically profiling patient tumors is considered for making clinical treatment decisions, recent methodologies for screening of genomic aberrations in circulating tumor cells (CTCs) and cell-free plasma DNA (cfDNA) may provide non-invasive tools for such applications. Genomic analysis of DNA from CTCs and plasma can also provide useful insight into tumor heterogeneity and thus disease progression by revealing sub-populations of tumor cells that evolve during treatment, have novel drug-resistant genotypes, or carry alternate cancer driver mutations not identified by the sequencing of primary tumors.

Comprehensive evaluation of DNA isolated from CTCs and cfDNA from a breast cancer patient by whole exome sequencing was performed to better understand the role of liquid biopsies in investigating the etiology of tumor progression. The patient was diagnosed with metastatic triple negative breast cancer (TNBC) six years after remission from estrogen receptor (ER-3+), progesterone receptor (PR-1+), human epidermal receptor growth factor 2 negative (Her2-), grade 3 intra-ductal carcinoma of the right breast. Metastatic lesions were found in the spine, pelvis and sacrum and bone-marrow. The patient was enrolled in the Intensive Trial of OMics in Cancer clinical Trial (ITOMIC-001; ClinicalTrials.gov ID NCT01957514) and initially received weekly cisplatin infusions followed by additional targeted therapy.

Peripheral blood was obtained during regular clinic visits over the 272 days the patient was enrolled in the clinical trial. CTCs were identified and enumerated from each blood draw using the AccuCyte® -CyteFinder® (AC/CF) system (RareCyte, Seattle WA). Multiple CTCs along with white blood cells (WBCs) were picked from various time points throughout the treatment regimen. The selected CTCs and WBCs were whole genome amplified and whole exome sequencing was performed to identify tumor specific variants. A comparative analysis with variants present in genomic DNA isolated from the bone-marrow metastasis tissue biopsy samples and cfDNA revealed the evolution of tumor-specific variants during therapy. Each CTC had somatic alterations in genes associated with therapies in current use or those in the clinical trials setting. Sequencing analysis of cfDNA provided similar information on potential therapeutic approaches. The monitoring of disease over time through genomic analysis of CTCs and cfDNA can identify novel sub-populations related to disease progression for the tailoring of cancer treatment regimens. Further analysis is being performed to better understand the evolution of the genomic heterogeneity among CTCs at the same time point and across different time points and therefore better understand the etiology of progression of metastatic breast cancer in this patient.

Citation Format: Howard K, Austin S, Ramirez AB, Ritter L, Boles D, Pruitt J, Collins H, Mahen E, Leonti A, Maassel L, Subia C, Tuuli S, Heying N, Deutsch K, Cox J, Lo FY, Stilwell JL, Kaldjian EP, Dorschner M, Blau S, Blau A, Eisenberg M, Anderson S, Madan A. Longitudinal analysis of circulating tumor cells and cell free tumor DNA by next generation sequencing in triple negative breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-02-21.