Poor tumor differentiation is an independent adverse prognostic variable in patients with locally advanced oral cavity cancer--Comparison with pathological risk factors according to the NCCN guidelines

Abstract

Methods: We sought to compare the prognostic impact of tumor differentiation with respect to adverse risk factors (RFs) identified by the National Comprehensive Cancer Network (NCCN) guidelines--including extranodal extension (ENE), positive/close margins, perineural invasion, lymphatic invasion, and vascular invasion--in patients with locally advanced oral cavity squamous cell carcinoma (OCSCC).

Results: Between 1996 and 2018, 1179 consecutive patients with first primary pT3-4 OCSCC were included. A three-level grading system was adopted--in which the final classification was assigned according to the most prevalent tumor grade. We identified 382/669/128 patients with well/moderately/poorly differentiated tumors, respectively. Compared with well/moderately differentiated tumors, poorly differentiated OCSCC had a higher prevalence of the following variables: female sex (4%/6%/11%), ENE, (14%/36%/61%), positive margins (0.5%/2%/4%), close margins (10%/14%/22%), perineural invasion (22%/50%/63%), lymphatic invasion (2%/9%/17%), vascular invasion (1%/4%/10%), and adjuvant therapy (64%/80%/87%). The 5-year rates of patients with well/moderately/poorly differentiated OCSCC were as follows: local control (LC, 85%/82%/84%, p = 0.439), neck control (NC, 91%/83%/70%, p < 0.001), distant metastases (DM, 6%/18%/40%, p < 0.001), disease-free survival (DFS, 78%/63%/46%, p < 0.001), disease-specific survival (DSS, 85%/71%/49%, p < 0.001), and overall survival (OS, 68%/55%/39%, p < 0.001). Multivariable analysis identified the following variables as independent prognosticators for 5-year outcomes: ENE (LC/NC/DM/DFS/DSS/OS), poorly differentiated tumors (NC/DM/DFS/DSS/OS), positive margins (LC/DFS), lymphatic invasion (DFS/DSS/OS), perineural invasion (DM), and age ≥65 years (OS).

Conclusions: In addition to ENE, poor tumor differentiation was identified as the second most relevant adverse RF for patients with pT3-4 OCSCC. We suggest that the NCCN guidelines should include poor tumor differentiation as an adverse RF to refine and tailor clinical management.

Keywords: histopathological risk factors; oral cavity; prognosis; squamous cell carcinoma; tumor differentiation.