Problem: In 2010, 23,880 new cases of oral cavity cancer were diagnosed and these were associated with 5,470 deaths. The prognostic implication of circulating tumor cells (CTCs) in oral squamous cell carcinoma (OSCC) has not been well-defined. The objectives of this research were: 1) To present and discuss a high performance negative depletion methodology for the isolation of CTCs in the blood of patients with OSCC, 2) To investigate whether or not a correlation exists between the presence of CTCs with specific histopathologic criteria and clinical outcomes.
Materials and Methods: A negative depletion process was used to isolate and quantify CTCs from the peripheral blood of patients with OSCC. This was accomplished by using an immunomagnetic separation method that was previously developed and validated. A histopathological review and prospective clinical follow-up study was evaluated from patients who had their peripheral blood examined for the presence CTCs at the time of surgical intervention.
This study included 24 patients, 26 to 81 years of age whom were diagnosed with OSCC. Blood samples were collected between March 2007 to July 2009 and an immunomagnetic enrichment method was used to begin the process of identifying circulating tumor cells. Immunostaining for cytokeratin was used to identify circulating CTCs, which were manually counted using fluorescent microscopy. A correlation analysis was performed to determine whether or not the presence of CTCs correlated with patients’ pathologic tumor stage, as well as the presence of perineural invasion, and lymphovascular invasion. In addition, a Kaplan-Meier plot was created to determine the significance of the presence of CTCs with regard to disease-free survival.
Results: For the 24 patients with OSCC, 17 (70.8%) had the presence of CTCs using the described negative depletion enrichment method. To date, pathologic stage and perineural invasion do not appear to correlate with the presence of CTCs, however lymphovascular invasion showed significant correlation (p=0.04). Clinical follow-up (range: 5-48 months), showed an early trend toward improved disease-free survival that was seen in patients with no identifiable CTCs, however, with longer follow-up, this has not shown significance (p=0.34).
Conclusions: An enrichment technology, based on the selective removal of normal cells, was used on the peripheral blood of patients with OSCC to identify CTCs. Histopathological characteristics of perineural invasion and tumor stage, which tend to relate to poor prognosis, do not appear to relate to the presence of CTCs. The presence of CTCs did correlate with lymphovascular invasion. The presence of CTCs was associated with a more aggressive early clinical course, and this brings into consideration the use of peripheral blood screening for CTCs as prognostic tool for patients with OSCC.