Abstract PR002: The clinical relevance of circulating tumor cell size in head and neck squamous cell carcinoma patients
Authors: Woo Hyeongjung , Shin Hyun Young , Oh So Yeon , Lee Sun Min , Kim Minseok S. 
Published: November 2024

Abstract
Circulating tumor cells (CTCs) play a critical role in the metastatic process of cancer and are widely recognized as important biomarkers that provide valuable information related to tumor characteristics. While most research to date has focused on the biological markers and molecular properties of CTCs, their physical characteristics, particularly size, have been relatively underexplored. However, recent studies suggest that smaller CTCs exhibit enhanced tumor- initiating and metastatic abilities compared to larger CTCs. This indicates that CTC size is not merely a physical trait but may directly influence the invasiveness and metastatic potential of tumors. Such findings suggest that CTC size could be an important indicator for predicting tumor malignancy and provide a new perspective on understanding cancer progression and metastasis. As such, there is a growing emphasis on research that considers the size of CTCs. In this study, it was speculated whether CTC size holds clinical significance in patients with head and neck squamous cell carcinoma (HNSCC). The study was involved with 20 HNSCC patients, analyzing the morphological characteristics of CTCs collected from blood samples before and after treatment, while exploring the potential for monitoring treatment response. Our results found that CTCs were detected 20% more frequently in oropharyngeal cancer (OPC) patients compared to non-OPC patients. This is likely due to the rich vascularity in the oropharyngeal region, which may facilitate greater entry of CTCs into the bloodstream. Additionally, the cell size (23.9 μm in average) and nuclear size (16.4 μm in average) of HPV-positive patients were 32% and 10% larger, respectively, than those of HPV-negative patients (cell size: 18.1 μm; nuclear size: 12.60 μm). This suggests that the sizes of CTC and their nuclei may be associated with HPV status, which is presumed to be due to HPV causing disruptions in the cell cycle. In addition, we could successfully cultivate the CTCs obtained from HPV-positive patients with relatively smaller CTCs for 30 days, predicting that small CTCs have affordable for CTC culture. In conclusion, this study confirms that the physical characteristics of CTCs, particularly size, are linked to HPV infection status in HNSCC patients. CTC- and nucleus- size are closely related to tumor characteristics, demonstrating the potential for developing diagnostic and prognostic tools based on these physical traits. Although more in-depth research is required, poor prognosis in HPV- positive patients may also be related to the physical characteristics of CTCs.
Citation Format: Hyeongjung Woo, Hyun Young Shin, So Yeon Oh, Sun Min Lee, Minseok S. Kim. The clinical relevance of circulating tumor cell size in head and neck squamous cell carcinoma patients [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr PR002.