Validating the AJCC 8th Edition of the Oral Cavity Cancer Staging System: A Multi-institutional Collaborative Study

Abstract

We conducted a multi-institutional study to interrogate survival outcomes in patients with oral cavity squamous cell carcinoma (OC-SCC) treated definitively grouped according to the AJCC 8th edition staging system and compared them to the 7th edition system for best fit analysis. An IRB approved collaborative database of patients with primary OC-SCC stage I-IVb (AJCC 7th edition) treated with primary surgical resection between 1/1/2005 and 1/1/2015 with or without adjuvant therapy was established from 6 academic medical centers. From a total sample size of 1282 patients, we identified 1037 patients who had sufficient staging data to be included. Survival rates were generated using Kaplan Meier analysis. A Cox proportional hazards model was generated for each staging system and Akaike information criterion (AIC) was calculated for each. The study population consisted of 647 men (62%), 868 Whites (84%) with a median age of 61 and a median f/u of 56 months (1-180). Oral tongue was the most common location (38%), followed by floor of mouth (18%), alveolus (14%) and other. All patients had primary resection, 91% had a neck dissection, 46% had postop radiation therapy alone and 37% had postop chemoradiation. The stage was changed in 388 pts (37%) in the 8th edition, all of whom were upstaged (see Table 1). Relative to stage I, AJCC 8 failed to show a significant difference in survival for stage II (HR 1.2; p=0.63) and stage III disease (HR 1.5; p=0.14), while stages IVa (HR 2.5; p<0.001) and IVb (HR 4.8; p<0.001) demonstrated significantly inferior survival. AJCC 8 5yr OS rates were similar compared to AJCC 7 for stage I (81%) and II disease (77% vs 75%), higher for stage III (72% vs 65%) and stage IVa disease (55% vs 47%), and lower for stage IVb disease (34% vs 44%), respectively. The AIC were smaller for AJCC 8 (5,804 vs. 5,841) indicating better fit. The AJCC 8th edition upstaged 37% of patients with OC-SCC leading to more uniform representation within each stage. The 8th edition outperformed the 7th edition in distinctiveness, most notably in stage IVa and IVb disease.Abstract 41; Table 1Distribution of patients according to AJCC stageAJCC 7AJCC 8TotalIIIIIIIVAIVBI804112--133II-6952--121III--11237-149IVA---379246625IVB----99Total801101764162551037 Open table in a new tab