Comparative impact of grade on mortality across salivary cancers: A novel, unifying staging system

BackgroundThe comparative impact of histologic variants and grade has not been well described. MethodsSalivary cancer histologies were profiled using hospital and population-based cancer registries. Multivariable models were employed to assess relationships between histology, grade, and survival. ResultsOn univariate analysis, histologic variants exhibited a wide spectrum of mortality risk (5-year overall survival (OS): 86% (acinic cell carcinoma), 78% (mucoepidermoid carcinoma), 72% (adenoid cystic carcinoma), 64% (carcinoma ex-pleomorphic adenoma), 52% (adenocarcinoma NOS), and 47% (salivary duct carcinoma) (p < 0.001). However, on multivariable analysis these differences largely vanished. Worsening grade corresponded with deteriorating survival (5-year OS: 89% [low-grade], 81% [intermediate-grade], 45% [high-grade]; p < 0.001), which was upheld on multivariable analysis and propensity score matching. Recursive partitioning analysis generated TNM + G schema (c-index 0.75) superior to the existing system (c-index 0.73). ConclusionGrade represents a primary determinant of salivary cancer prognosis. Integrating grade into stage strengthens current staging systems.

Automated summary

This study investigated the impact of histologic variants and grade on the prognosis of salivary cancer. The results showed that histologic variants had different mortality risks, but these differences were diminished in multivariable analysis. In contrast, worsening grade was strongly associated with deteriorating survival. Integrating grade into stage can improve the predictive ability of the current staging system.