Radical (chemo)radiotherapy in a population-based dataset of real-world patients with oropharyngeal cancer: comparison of 7th and 8th staging systems


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Francesca De Felice1,Thomas Bird2,Andriana Michaelidou3,Selvam Thavaraj4,Edward Oddell4,Ann Sandison4,Gillian Hall4,Peter Morgan4,Andrew Lyons4,Luke Cascarini4,Alastair Fry4,Richard Oakley4,Ricard Simo4,Jean Pierre Jeannon4,Miguel Reis Ferreira4,Mary Lei4,Teresa Guerrero Urbano4
1Guy's and St Thomas' NHS Foundation Trust, London, Sapienza University of Rome, Rome, Italy,2Bristol Cancer Institute, Horfield Road, Bristol, BS2 8ED,3King's College London and Kent Oncology Centre,4Guy's and St Thomas' NHS Foundation Trust

Abstract

Background

To evaluate if the 8th staging system is a better discriminator of overall survival (OS) than the 7th edition in oropharyngeal cancer patients after definitive (chemo)radiotherapy (CRT).

Method

Data from oropharyngeal cancer patients treated with a curative CRT between 2010 and 2016 were reviewed. The p16 status was ascertained in all cases. Patients were prospectively staged on the 7th and retrospectively on the 8th edition systems. Demographics, tumor characteristics and treatment response data were included in univariate and multivariate analysis for OS. OS and disease-free survival (DFS) were estimated using the Kaplan-Meier method.

Results

273 patients were included. Median follow-up was 4.7 years. Overall 63 patients died. In multivariate analysis, p16 status, complete response at 3 months and ≤ 21 units/week alcohol were prognostic for OS. For the entire cohort, 5-year OS and DFS were 78.1% (95% confidence interval CI 0.719 - 0.831) and 73.9% (95%CI 0.677 - 0.792), respectively. 

When the 8th edition was used, there was a shift to stages I-II mainly due to lymph node staging reclassification. p16-positivity, a previously identified risk stratification approach, resulted in statistically higher discrimination in both OS rates (5-year OS 90.7% in low risk patients and 84.6% in intermediate risk, p = 0.05) and DFS rates (5-year DFS 91.5% in low risk and 76.1% in intermediate risk, p = 0.001).

Conclusion

TNM 8th edition provides better OS and DFS stratification in oropharyngeal cancer after definitive CRT compared to the 7th edition. Further analysis of additional clinical variables, such as complete response at 3 months, alcohol and smoking habits, is warranted to further refine prognostic groups in oropharyngeal cancer.