Validation of the ICON-S staging for HPV-associated oropharyngeal carcinoma using a pre-defined treatment policy.

OBJECTIVES: To determine whether the International Collaboration on Oropharyngeal cancer Network for Staging (ICON-S) for HPV associated oropharyngeal carcinoma (HPV+OPC) is a better discriminator of overall survival (OS), compared with the 7th edition (7th Ed) AJCC/UICC TNM staging following curative radiotherapy (RT). MATERIAL AND METHODS: The 5-year OS for all patients with non-metastatic (M0) p16-confirmed OPC treated between 2005 and 2015 was determined and grouped based on the 7th Ed AJCC/UICC TNM and ICON-S staging. RESULTS: A total of 279 patients met the inclusion criteria. The 5-year OS with the 7th Ed TNM classification were Stage I/II 88.9% (95% CI; 70.6-100%), Stage III 93.8% (95% CI; 85.9-100%), Stage IVa 86.4% (95% CI; 81.6-91.5%) and Stage IVb 62.3% (95% CI; 46.8-82.8%). On multivariate Cox regression analysis there was no statistically significant OS difference when comparing Stage I/II with, Stage III (p=0.98, HR=0.97, 95% CI; 0.11-8.64), IVa (p=0.67, HR=1.56, 95% CI; 0.2-11.94) and IVb (p=0.11, HR=5.54, 95% CI; 0.69-44.52), respectively. The 5-year OS with ICON-S staging were Stage I 93.6% (95% CI; 89.4-98.0%), Stage II 81.9% (95% CI; 73.7-91.1%) and Stage III 69.1% (95%; 57.9-82.6%). There was a consistent decrease of OS with increasing stage. On multivariate Cox regression analysis, when compared to Stage I, OS was significantly lower for stage II (p=0.007, HR=2.84, 95% CI; 1.33-6.05) and stage III (p<0.001, HR=3.78, 95% CI; 1.81-7.92), respectively. CONCLUSION: The ICON-S staging provides better OS stratification for HPV+OPC following RT compared with the 7th Ed TNM staging.