The Impact of Surgery on Circulating Malignant Tumour Cells in Oral Squamous Cell Carcinoma

SIMPLE SUMMARY: Question: What impact does resective surgery have on circulating malignant cells in patients with oral squamous cell carcinoma? Findings: This case series showed that surgery increased both single circulating tumour cells and clusters of malignant cells in the circulation. Circulating endothelial cells were also detected in the majority of patients. These three types of circulating malignant cells were persistently detected up to the seventh post-operative day despite M0 status and clear surgical margins. Meaning: Surgical management has the potential to systemically disseminate oral squamous cell carcinoma. ABSTRACT: Importance: The extent to which surgical management of oral squamous cell carcinoma (OSCC) disseminates cancer is currently unknown. Objective: To determine changes in numbers of malignant cells released into systemic circulation immediately following tumour removal and over the first seven post-operative days. Design: An observational study from March 2019 to February 2021. Setting: This study was undertaken at Queen Mary University Hospital, Hong Kong. Participants: Patients with biopsy-proven oral SCC were considered for eligibility. Patients under 18 years of age, pregnant or lactating women and those unable to understand the study details or unable to sign the consent form were excluded. Twenty-two patients were enrolled (12 male and 10 female) with mean age of 65.5 years. Intervention: Primary tumour management was performed in accord with multi-disciplinary team agreement. Anaesthesia and post-operative care were unaltered and provided in accord with accepted clinical practice. Main Outcomes and Measures: Three types of malignant cells detected in peripheral blood samples were enumerated and sub-typed based on the presence of chromosomal aneuploidy and immunohistochemical characteristics. To test the hypothesis that malignant cells are released by surgery, the numbers of single circulating tumour cells (CTCs), circulating tumour microemboli (CTM) and circulating endothelial cells (CTECs) were recorded pre-operatively, upon tumour removal and the second and seventh post-operative days. Results: Of a potential 88 data collection points, specimens were not obtainable in 12 instances. Tumour removal resulted in a statistically significant increase in CTCs and a non-statistically significant rise in CTMs. CTCs, CTMs and CTECs were detected in the majority of patients up to the seventh post-operative day. Individual patients demonstrated striking increases in post-operative CTCs and CTECs numbers. Conclusions/Relevance: Surgical management of OSCC has a significant impact on the systemic distribution of cancer cells. Malignant cells persisted post-operatively in a manner independent of recognised staging methods suggesting differences in tumour biology between individuals. Further investigation is warranted to determine whether circulating malignant cell enumeration can be used to refine risk stratification for patients with OSCC.