Tetranucleotide microsatellite instability in surgical margins for prediction of local recurrence of head and neck squamous cell carcinoma.

Postoperative radiotherapy is used to prevent local recurrence of head and neck squamous cell carcinoma in patients with positive surgical margins. We sought to determine whether tetranucleotide microsatellite instability could be detected in surgical margins and used to predict local recurrence. We prospectively collected tumor and surgical margin specimens from patients with head and neck squamous cell carcinoma who had undergone surgical resection at Institut Gustave-Roussy during a 1-year period. Margins were considered positive if extensive pathological examination revealed either carcinoma within 5 mm or dysplasia. We tested five tetranucleotide microsatellite markers (UT5085, L17686, D9S753, ACTBP2, and CSF1R) in the tumor specimens and paired surgical margins of the patients whose margins were negative on pathological examination. Pathological examination revealed that among the 76 patients, 22 had positive margins; therefore, these patients were excluded. Of the 54 remaining patients, 26 (48%) had tumors informative for markers UT5085, L17686, or both; the other 3 markers were not informative. Seven (27%) of the 26 informative tumors had the same instability pattern in the surgical margins. At a median follow-up of 26 months, 5 of the 7 local recurrences occurred in patients with molecularly positive surgical margins. A strong, independent association was found between positive surgical margins and local recurrence (P = 0.01; hazard ratio, 6.49). Tetranucleotide microsatellite instability in surgical margins may be a useful biomarker to predict local recurrence of head and neck squamous cell carcinoma in patients with apparently disease-free margins.