Abstract PR007: Comprehensive ctDNA profiling reveals potential metastatic genomic signatures in treatment-naive early-stage breast cancer patients
Authors: Shafi Gowhar , Dongare Manoj , Bharde Atul , Fauzul Moubeen , Hariramani Kanchan , D’Souza Alain , Jadhav Bhagwat , Kad Trupti , Prajapati Sangeeta , Jadhav Vikas , Kumaran ManojKumar , Haldar Sumit , Mehra Vatsal , Joshi Sujit , Aland Gourishankar , Dave Richa , Jayant Sreeja , Vasudevan Aravindan , Uttarwar Mohan , Khandare Jayant 
Published: January 2023

Abstract
Background: Genomic profiling has revolutionized precision oncology impacting the diagnosis, prognosis, and therapy decisions. Considering high spatiotemporal diversity and heterogenicity of breast tumor-cell genomes, small-gene panels often fail to capture rare but important genomic alterations. Conversely, comprehensive ctDNA sequencing approaches enable the identification of under characterized ‘long tailed driver’ genomic alterations and capture Intra and inter metastatic heterogeneity. Here, we demonstrate the clinical utility of comprehensive genome profiling with higher sensitivity to predict the possibility of metastasis in early-stage breast cancer patients. Methods: We retrospectively analyzed ctDNA and genomic DNA (gDNA) from FFPE samples as well as circulating tumor cells (CTC) in 10 treatment-naive hormone positive and HER2 negative, primary-stage breast cancer patients [GS1] using the OncoIndx comprehensive 600 gene panel. The panel captures all important cancer-relevant genomic alterations including Tumor Mutation Burden (TMB), Micro Satellite Instability (MSI), homologous recombination deficiency (HRD) prediction, and cfDNA tumor fraction (TF). CTCs were enumerated from 1.5 ml of blood using the OncoDiscover platform approved by the Drug Controller General of India having anti-EpCAM antibody-mediated immunomagnetic nanoparticles. CTCs were confirmed for cytokeratin 18+ and DAPI + markers and the absence of CD45. Results: Comprehensive genomic profile obtained from ctDNA and gDNA from FFPE of early-stage breast cancer patients predominantly exhibited the presence of alterations in PIK3CA and ESR1 signaling pathways. PIK3CA mutations were present in 77% and 44% of baseline ctDNA and gDNA samples, while ESR1 mutations were present in 44% and 22% of baseline ctDNA and gDNA, respectively. In addition, we observed about 70% additional driver mutations in ctDNA samples suggesting shedding of ctDNA together with CTC (80% positive), a likely positive biomarker of metastasis. About 50% of the patients showed higher TMB and HRD. Notably, TF representing ctDNA varied between 13% to 27% in blood samples with a corresponding ploidy range of 2.9 to 4.7. Surprisingly, ~50% of the patient population matched the mutation profile of clinically confirmed metastatic patients. All the patients harboring potential metastatic driver alterations showed the presence of CTCs in peripheral blood. Conclusions: Comprehensive ctDNA genomic profiling showed potential metastasis driving alterations suggesting the role of ctDNA-based liquid biopsy to predict metastasis in early breast cancer patients. We observed enhanced TF at the time of diagnosis, possibly due to the presence of distant metastasis, high disease burden, and aggressive tumor biology. Our results suggest that ctDNA dynamics at the time of disease presentation can predict early metastasis, and may demonstrate the divergent response of tumor heterogeneity to treatment in early-stage breast cancer.
Citation Format: Gowhar Shafi, Manoj Dongare, Atul Bharde, Moubeen Fauzul, Kanchan Hariramani, Alain D’Souza, Bhagwat Jadhav, Trupti Kad, Sangeeta Prajapati, Vikas Jadhav, ManojKumar Kumaran, Sumit Haldar, Vatsal Mehra, Sujit Joshi, Gourishankar Aland, Richa Dave, Sreeja Jayant, Aravindan Vasudevan, Mohan Uttarwar, Jayant Khandare. Comprehensive ctDNA profiling reveals potential metastatic genomic signatures in treatment-naive early-stage breast cancer patients [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr PR007.