Impact of changes to the American Joint Committee on Cancer T classification on outcome prediction in patients with oropharyngeal cancer.

Background: The efficacy of the current 6th edition of the American Joint Committee on Cancer (AJCC) tumor staging criteria in improving outcome prediction for patients with oropharyngeal cancer was analyzed.

Methods: From the database of the Department of Radiation Oncology at the University of Texas M. D. Anderson Cancer Center the authors identified 875 patients irradiated at the study institution for oropharyngeal cancer between January 1975 and December 1998. The tumors were restaged based on the 6th edition of AJCC tumor staging criteria to reassess the original outcome predictions, specifically overall survival (OS) and local control (LC).

Results: Applying the new 6th edition staging system resulted in the following T classification distributions: T2, 301 tumors (34%); T3, 248 tumors (28%); T4a, 224 tumors (26%), and T4b, 102 tumors (12%). The 5-year and 10-year OS rates based on the new system were: T2, 65% and 45%; T3, 44% and 28%; T4a, 30% and 23%; and T4b, 26% and 12%, respectively. The 5-year and 10-year actuarial local LC rates based on the new system were: T2, 85% and 83%; T3, 73% and 71%; T4a, 61% and 58%; and T4b, 42% and 42%, respectively. Differences in OS and LC rates stratified by stage were found to be statistically significant both for the overall distribution of survival and pairwise comparisons of the 4 tumor stage groups.

Conclusions: The modifications established in the 6th edition of the AJCC tumor staging system for oropharyngeal tumors appear to be useful to distinguish prognostic groups for both LC and OS based on tumor stage.