Background:
The American Joint Committee on Cancer (AJCC) has recently made two major changes
in the staging system of oral squamous cell carcinoma (oSCC) in the 8th edition. One
is the inclusion of depth of invasion (DOI) of the primary tumor as a modifier to
the T category and second, extranodal extension (ENE) is introduced to upstage nodal
positive oSCC. This study aims to evaluate the performance of the AJCC 8 staging system
and compare it to its predecessor (AJCC 7).
Methods:
Analysis of 663 patients with oSCC from a prospective database was performed. Multivariable
analysis was performed using Cox proportional hazards competing risk model. To assess
staging system performance an explained variation measure (Proportion of explained
variation, PVE) and a discrimination measure (Harrell's concordance index, C-index)
was used.
Results:
Within the patient group, 35.6% (N = 235) were upstaged by AJCC 8. AJCC 8 shows weak
separation and limited monotonicity especially of the stage groups I to III. The estimates
for model performance reveal modest predictive capacity of AJCC 8 for overall survival
(OS) and disease specific survival (DSS) (Harrell's C of 0.70 and 0.74, respectively)
but improved predictive capacity compared to AJCC 7 (Harrell's C of 0.69 and 0.65,
respectively).
Conclusions:
The staging system of AJCC 8 is more complex than its former version due to the inclusion
of DOI and ENE. Compared to AJCC 7 it performs better in stratifying survival of oSCC
patients by their stage. Nevertheless the estimates for model performance reveal still
a limited utility and its applicability in daily clinical practice seems problematic.
