Declining Proportion of Incident Squamous Cell Carcinomas of the Oral Cavity Coded as Unknown for American Joint...

For squamous cell carcinomas of the oral cavity (OCSCC), American Joint Committee on Cancer (AJCC) TNM stage at diagnosis is widely used by clinicians. In US cancer registries, AJCC 6th edition stage was derived by computer algorithm from codes based on the Collaborative Stage System (CSS) for diagnoses from 2004-2015, but unknown stage is an issue.

A research database of population-based Surveillance, Epidemiology, and End Results (SEER) Program registries (covering about 28% of the US population) included AJCC stage for diagnoses in 2004-2014. Trends (2004-2014) were examined in the proportion of invasive OCSCC cases coded as unknown vs known (ie, I-IV) for AJCC stage group.

The proportion with AJCC stage unknown declined from 22.5% for 2004 to 12.3% for 2014, reaching as low as 9.8% for age 45-64 years (although higher for older age groups) and 8.1% for all cases with cancerdirected surgery. The largest decline was for the T (tumor size/local extension) component of TNM. The proportion coded as stage IV increased from 22.1% for 2004 to 31.5% for 2014.

The proportion with unknown AJCC stage declined substantially. Surveillance (including non-SEER registries) is needed using registry coding of extent of disease that has replaced CSS, and after the advent of registry coding using the AJCC 8th edition, which includes changes in staging of OCSCC that are relevant to clinicians.