Histological Grade As a Predictor of Oral Cancer Survival

Objective: Some recent studies suggest an association between the histological grade of oral cancer and relative survival rates. The purpose of this study was to explore that relationship.

Methods: Data for incident oral cancer (ICD-O 1.9-6.9) cases were obtained from the Surveillance, Epidemiology, and End Results (SEER) Program and used to calculate 8-year relative survival rates stratified by race, gender, age (<50, 50+), anatomical site, stage at diagnosis, and histological grade of differentiation. SEER* Stat was used to perform all analyses using the Actuarial method. The study included only first primary cancer cases diagnosed during 1996 through 2003, who were actively followed and whose tumors were invasive. Cases identified by death certificate or autopsy only were excluded from the analysis.

Results: Histological grade was a good predictor of relative survival among White males (both <50 and 50+) diagnosed with a localized stage of oral cancer (all sites combined). Grade 1 differentiation (highly differentiated) had the highest relative survival rates, while grades 2 (moderately differentiated) and 3 (poorly differentiated) had progressively lower survival rates, respectively. In sub-site analyses of survival data for White males (50+) with localized disease, the same pattern was observed for the anterior 2/3 of the tongue, but not for the floor of mouth or other sites. When White women (50+) with a localized stage of oral cancer (all sites combined) were analyzed separately, the highest relative survival rates were seen for grade 2. Finally, when White males (50+) diagnosed with a regional stage of oral cancer (all sites combined) were considered, survival rates were not notably different by grade; however, survival rates were generally highest for grade 3 and lowest for grade 2.

Conclusion: Based upon SEER data, histological grade did not consistently predict 8-year relative survival across specific anatomical sites, gender or stage at diagnosis.