Prognosis of oral cancer: a comparison of the staging systems given in the 7th and 8th editions of the American Joint Committee on Cancer Staging Manual

The 8th edition of the American Joint Committee on Cancer (AJCC) Staging Manual introduces "depth of invasion" and "extranodal extension" into the head and neck section, and our aim was to find out if these changes have an impact on prognosis. We evaluated 174 patients who had had oral squamous cell carcinomas (SCC) resected between 2003 and 2012. The clinical records were reviewed, the patients' tumours restaged according to the 8th edition of the AJCC, and we analysed five-year survival to verify whether different correlations were made between the T and N stages and disease-specific survival using the 7th and 8th editions. We excluded seven cases because information was incomplete, and the final sample was 167 patients. The five-year overall survival was 68% and the five-year disease-specific survival was 78%. The variable pT was upstaged in 51 patients (31%), and no tumour was downstaged. When we used the 7th edition, the pT category did not correlate with survival (p=0.055), but when we used the 8th edition, there was a significant association between increased pT categories and disease-specific survival (p=0.01). In the pN category 23 cases were upstaged (14%) and this affected disease-specific survival using both the 7th and the 8th editions (p=0.001). When patients were restaged, there was an improvement in discrimination between T categories in relation to disease-specific survival, and confirmation of the prognostic impact of the variable pN. T stage and depth of invasion are complementary predictors of disease-specific survival, and their combination results in the new AJCC staging system giving a better prognosis.