Grade as a prognostic factor in oral squamous cell carcinoma: a population-based analysis of the data.

Abstract

Historically, histologic grade has not been considered a useful prognostic factor in head and neck squamous cell carcinoma (SCC). However, in other solid tumors, grade is known to affect prognosis. We test the hypothesis that histologic grade is an independent predictor of prognosis in oral cavity SCC. Population-based cohort study using the Surveillance, Epidemiology, and End Results (SEER) database of the National Cancer Institute. Fifteen year cause-specific survival. Multivariate analysis was performed on a subset of patients diagnosed between 2004 and 2008. Among patients 20 to 65 years of age with American Joint Committee on Cancer (AJCC) stage I or II cancer, the adjusted risk of death is 2.7 times greater (95% CI 1.72-4.11) if the tumor is poorly differentiated or undifferentiated than it is if the tumor is well differentiated. Among patients 66 to 94 years of age, the risk of death is 3.0 (95% CI 2.02-4.54) times greater. For those over age 65, moderately differentiated tumors also confer an estimated 42% increased risk of death, but this estimate is only borderline significant (P = 0.05). There is a strong association between histologic grade and survival in patients with AJCC stage I or II oral cavity SCC. High histologic grade in early stage oral cavity cancer is associated with poorer survival and carries independent prognostic value in addition to tumor size, node status, and presence of distant metastasis (TNM) stage. Thus, histologic grade should be considered clinically when making treatment decisions, and multivariable models of survival should include grade as a covariate to improve prognostic accuracy.