Abstract A49: Viable circulating ensembles of tumor-associated cells persist in pretreated patients with solid organ cancers showing no radiologically detectable disease

The success of treatment in solid organ cancers is ascertained by radiologic imaging as per standard-of-care protocol, with PET-CT being the modality of choice. However, even in cases where complete resolution of the disease is noted radiologically, recurrence or emergence of new metastases is not uncommon. To explore the underlying cause of such recurrence, we hypothesized that circulating metastatic disease (CMD) in the nature of viable tumor cells or clusters would be a persistent systemic feature of solid organ cancers, although there may be no overt evidence of disease. We identified 1,217 patients with known and previously treated cases of various solid organ cancers (metastatic and nonmetastatic), where a recent PET-CT scan showed no radiologic evidence of disease. 15 mL peripheral blood was collected from these patients. Peripheral blood mononuclear cells (PBMCs) were harvested by centrifugation. Circulating ensembles of tumor-associated cells (C-ETACs) were enriched from PBMCs using an epigenetically acting stabilization process, which is cytotoxic towards nonmalignant cells but confers survival privilege on apoptosis-resistant cells of tumorigenic origin as well as their heterotypic clusters (C-ETACs). C-ETACs were characterized by immunostaining for EpCAM, pan-CK, and CD45 as well as for organ-specific markers. Among the 1,217 patients with no radiologic evidence of disease, C-ETACs were detected in 1,118 (91.9%) and were confirmed by immunostaining. In a subset analysis, C-ETACs from 80 samples were immunostained for organ- or subtype-specific antigens including those from head and neck (P63), breast (GCDFP15), colorectum (CDX2), liver (Hep Par-1), ovary (CA125), prostate (PSMA), cervical (P63), and lung (TTF-1/Napsin-A). Circulating metastatic disease (CMD) in the form of viable C-ETACs is a potent threat in patients with solid organ cancers despite complete radiologic response to treatment. Citation Format: Sewanti A. Limaye, Timothy Crook, Dadasaheb Akolkar, Darshana Patil, Pradip Devhare, Revati Patil, Shoeb Patel, Shabista Khan, Raja Dhasarathan, Vineet Datta, Cynthe Sims, Ajay Srinivasan, Rajan Datar. Viable circulating ensembles of tumor-associated cells persist in pretreated patients with solid organ cancers showing no radiologically detectable disease [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr A49.