Association between central and peripheral circulating tumor cell (CTC) clusters in oral squamous cell carcinoma (OSCC): A prospective, observational study.

Abstract

e15548 Background: Around 90% of cancer-related mortalities are caused by tumor metastasis. CTC clusters, which constitute an intermediate stage of metastasis, have not been studied extensively in head & neck cancers. The mortality rate of oral cancers remains alarmingly high, despite multimodality treatment. The aim of the study is to identify the presence of CTC clusters in patients with Oral Squamous Cell Carcinoma (OSCC) and to correlate their presence with clinical and pathological factors. Methods: Fifty patients diagnosed with histologically proven OSCC, treatment naïve, and underwent surgery at HCG Cancer Centre, Bangalore, were consented and enrolled in the study. An IRB-approved protocol allowed for the collection of 10 ml of blood from central (jugular) and peripheral veins intra-operatively, prior to tumor removal. The culturing of CTC clusters was done using ellipsoidal microwell plates maintained at hypoxic conditions, at the Institute of Bioinformatics, Bangalore. After fourteen days of culturing, the cells were fixed and stained for DAPI, Pan-CK and CD45. The CTC clusters were classified into Loose, Tight and very Tight based on the median gray values obtained from DAPI staining on ImageJ software. Clinical data was collected from patient records and subjected to analysis using Descriptive statistics. Results: From the 50 patients included in the study, 22 (44%) patients exhibited tight clusters in central blood, while only 13 (26%) patients exhibited tight clusters in peripheral blood. A higher clinical stage was observed in a greater percentage of patients with tight clusters in central blood (early: 45.5% versus late: 54.5%), but the same findings could not be inferred with pathological staging (early stage: 59.1% versus late stage: 40.1%). No significant correlation with adverse pathological features was noted. Conclusions: This observational study provides an insight into the varying biological behaviours of similarly grouped cancers, which is based on the standard TNM staging. The study forms the basis for the hypothesis of tight clusters in the central and peripheral circulation, correlating with loco-regional and distant metastasis respectively, thus leading to poorer disease-free and overall survival rates.