Microsatellite analysis of serum DNA in patients with head and neck cancer

We have shown previously that microsatellite alterations in serum DNA was predictive of distant metastasis in a study with 21 primary head and neck squamous cell carcinoma patients. To further investigate serum microsatellite alterations as a prognostic tool, we carried out microsatellite analysis of serum DNA with 10 markers on 152 patients with head and neck cancer. Forty-five percent (68/152) of patients had microsatellite alterations of serum DNA identical to corresponding tumor DNA. In 16 patients that had distant metastasis, 11 patients had a positive serum test (microsatellite alterations detectable in their serum DNA with one or more markers). The difference in distant metastasis rates between the negative and positive serum tests (6.0% [5/84] vs. 16.2% [11/68], RR = 2.7) was clinically significant and almost reached statistical significance (p = 0.06). When the analysis was restricted to patients with recurrent disease, a positive serum test correlated with those who developed distant metastasis (p = 0.04). Other parameters, such as development of recurrence, stage of the cancer, disease-free survival and overall survival, were not associated with a positive serum test. Detecting tumor DNA in serum by microsatellite analysis may help identify patients at risk for distant metastasis. Therefore, circulating tumor cells may contribute to the presence of tumor DNA in the serum. In the future if a serum test is positive, therapeutic approaches may by intensified, such as platinum-based chemoradiation, to reduce distant failures.