Background:Cisplatin-radiotherapy is a preferred standard for locally advanced, head and neck squamous cell carcinoma (HNSCC). However, the cisplatin-attributable survival benefit is small and toxicity substantial. A biomarker of cisplatin resistance could guide treatment selection and spare morbidity. The ERCC1-XPF nuclease is critical to DNA repair pathways resolving cisplatin-induced lesions.Methods:In a phase II trial, patients with untreated Stage III-IVb HNSCC were randomised to cisplatin-radiotherapy with/without erlotinib. Archived primary tumours were available from 90 of 204 patients for this planned substudy. Semi-quantitative ERCC1 protein expression (H-score) was determined using the FL297, 4F9, and 8F1 antibodies. The primary analysis evaluated the relationship between continuous ERCC1 protein expression and progression-free survival (PFS). Secondary analyses included two pre-specified ERCC1 cutpoints and performance in HPV-associated disease.Results:Higher ERCC1 expression was associated with inferior PFS, as measured by the specific antibodies FL297 (HR=2.5, 95% CI=1.1–5.9, P=0.03) and 4F9 (HR=3.0, 95% CI=1.2–7.8, P=0.02). Patients with increased vs decreased/normal ERCC1 expression experienced inferior PFS (HR=4.8 for FL297, P=0.003; HR=5.5 for 4F9, P=0.007). This threshold remained prognostic in HPV-associated disease.Conclusion:ERCC1-XPF protein expression by the specific FL297 and 4F9 antibodies is prognostic in patients undergoing definitive cisplatin-radiotherapy for HNSCC, irrespective of HPV status
