Validating the AJCC 8th Edition of the Oral Cavity Cancer Staging System: A Multi-institutional Collaborative Study

AJCC 8th Versus AJCC 7th as a Prognostic Indicator in Buccal Mucosal Squamous Cell Carcinoma

American Joint Committee for Cancer (AJCC) staging manual has been recently updated with 8th edition which led to an immense shift in the tumor, node, and composite stages, in comparison to the previous staging. This was mainly due to the incorporation of depth of invasion (DOI) and extranodal extension (ENE) in staging. The impact of new staging system is widely studied as combined subsites in oral cancer. This study is to focus on a single subsite of oral cavity which is known for its poor prognosis. We evaluated 109 patients who had buccal mucosal squamous cell carcinomas (BSCC) who underwent treatment, with a curative intend, between 2014 and 2015. Clinical records were reviewed and the tumors were re-staged as per 8th edition of AJCC; disease-free survival (DFS) was also analyzed. Our study population had a mean age of 54.5 ± 10.35 years and male to female ratio of 4:1. During a median follow-up of 41 months, 35 patients (32.1%) developed recurrence. There was a statistically significant shift in stages between AJCC 7th edition against AJCC 8th edition leading to 34% upshift in T-stage, 43.1% upshift in N-stage, eventually leading to a 23.9% upshift in the composite stage. Tumors which got upgraded due to upshift in nodal stage had a poor survival (p = 0.002). Newer staging system is easy to use in clinical practice. Around a quarter of the BSCC got upstaged with the introduction of the newer staging system. But it was surprising to note that there were no statistically significant differences in DFS between the tumors of the same composite stages with regard to the two staging systems.

Predictive nomograms for oral tongue squamous cell carcinoma applying the American Joint Committee on Cancer/Union Internationale Contre le Cancer 8th edition staging system

BACKGROUND

Nomograms applying the 8th edition of the TNM staging system aimed at predicting overall (OS), disease-specific (DSS), locoregional recurrence-free (LRRFS) and distant recurrence-free survivals (DRFS) for oral tongue squamous cell carcinoma (OTSCC) are still lacking.

METHODS

A training cohort of 438 patients with OTSCC was retrospectively enrolled from a single institution. An external validation set of 287 patients was retrieved from two independent institutions.

RESULTS

Internal validation of the multivariable models for OS, DSS, DRFS and LRRFS showed a good calibration and discrimination results with optimism-corrected c-indices of 0.74, 0.75, 0.77 and 0.70, respectively. The external validation confirmed the good performance of OS, DSS and DRFS models (c-index 0.73 and 0.77, and 0.73, respectively) and a fair performance of the LRRFS model (c-index 0.58).

CONCLUSIONS

The nomograms herein presented can be implemented as useful tools for prediction of OS, DSS, DRFS and LRRFS in OTSCC.

Geographical heterogeneity in the American Joint committee on Cancer oral cancer staging and prognostic implications

OBJECTIVES

The AJCC 8th edition (AJCC 8) has introduced depth of invasion (DOI) and extranodal extension (ENE) into staging for oral squamous cell carcinoma (OSCC). Although validations have been performed on institutional datasets have shown a good performance, particularly in early OSCC, there have been no studies on diverse patient populations that determine the impact on prognostic heterogeneity.

MATERIALS AND METHODS

Retrospective analysis of 4710 patients with oral squamous cell carcinoma (OSCC) treated with surgery +/- adjuvant therapy in 8 institutions in Australia, North America and Asia. With overall survival (OS) as endpoint, the prognostic performance of AJCC 7th and 8th editions were compared using Akaike Information Criterion (AIC), Bayesian Information Criteria (BIC), Harrell's concordance index (C-index).

RESULTS

When comparing AJCC 8 to AJCC 7, the heterogeneity in prediction of OS increased for T-category and N-category while remaining unchanged for TNM staging, suggesting AJCC 8 increased complexity with no improvement in predictive value. There were significant differences in median DOI and incidence of ENE between geographical regions, resulting in dissimilar rates of stage-migration when adopting AJCC 8.

CONCLUSION

In an attempt to improve prognostic performance, AJCC 8 introduced more variables; however heterogeneity in these results in significant geographical differences in model discrimination and performance. Caution should be applied as this may result in inaccurate and unreliable prognostic predictions that may impact treatment recommendations.