Validation of the eighth edition AJCC staging system in early T1 to T2 oral squamous cell carcinoma

Background To validate the newly proposed American Joint Committee on Cancer (AJCC) eighth edition staging in early T1 and T2 oral cavity cancers and its effect in predicting tumour control. Methods Retrospective analysis of treatment outcomes of 441 T1 to T2 oral squamous cell carcinoma (OSCC). Overall survival (OS), disease-specific survival (DSS), and tumour control were calculated and compared between the AJCC 7 and 8 staging systems. Results The 5-year OS was 78% and 61% for T1 and T2 tumours, respetively (P < 0.001) (AJCC 7) vs 87% and 67% (P < 0.001) (AJCC 8). The 5-year DSS was 78% and 61% for T1 and T2, respectively (P < 0.001) (AJCC 7) vs 89% and 71% (P < 0.001) (AJCC 8). For stages I and II tumours the 5-year OS was 81% and 76%, respectively (P < 0.302) (AJCC 7) vs 87% and 73% (P < 0.017) (AJCC 8). The 5-year DSS was 83% and 82% (P < 0.222) vs 89% and 77% (P < 0.016). With the AJCC eighth edition the 5-year local, regional, and distant control rates for T1 vs T2 tumours were 85% vs 74% (P = 0.003), 95% vs 77% (P = 0.001), and 95% vs 80% (P = 0.014), respectively. Conclusion The AJCC 8th staging system provided for more accurate prediction of OS, DSS, and disease control in early oral cavity cancers.