Assessment of the external validity of the American Joint Committee on Cancer 8th staging system for anal carcinoma

Abstract

Background: The current study evaluates the prognostic value of the 8th edition of the American Joint Committee on Cancer (AJCC) staging system for patients with anal carcinoma.

Patients and methods: The Surveillance, Epidemiology and End Results (SEER) database (2004–2014) was explored and AJCC 6th and 8th stages were formulated. Through Kaplan–Meier analysis, overall survival analyses were performed. The Cox regression model (adjusted for age, gender, histology, ethnicity, subsite and grade) was calculated for cancer-specific survival and, subsequently, pairwise comparisons of hazard ratios were calculated.

Results: A total of 11,934 anal carcinoma patients were included in the analysis. Overall survival was compared according to both AJCC 6th and 8th systems. For both staging systems, the p value for the trend in overall survival was significant (p < .0001). Nevertheless, for the AJCC 6th system, stage IIIA and IIIB curves were overlapping; while for the AJCC 8th system, the median survival for stage IIB was lower than the mean survival for stage IIIA (74 months vs. 96 months). Moreover, stage IIIB and stage IIIC curves were overlapping. The cause-specific (cancer-specific) Cox regression hazard was calculated for both staging systems. Pairwise hazard ratio comparisons between different AJCC 6th stages were performed and all p values for comparisons were significant (p < .05). Pairwise hazard ratio comparisons between different AJCC 8th stages were performed and only the following comparisons were significant (p < .0001) (I vs. IIA; IIA vs. IIB; IIIC vs. IV). The C-statistic (using death from anal carcinoma as the dependent variable) for the AJCC 6th staging system was: 0.681 (SE: 0.009; 95% CI: 0.664–0.698); while the C-statistic for the AJCC 8th staging system was 0.687 (SE: 0.008; 95% CI: 0.670–0.703).

Conclusions: There is no evidence of significant improvement in the AJCC 8th edition compared to AJCC 6th (or 7th) edition in terms of overall or cancer-specific survival prediction.

Keywords:

• Anal carcinoma
• AJCC
• staging
• prognosis
• SEER

Transparency

Declaration of funding

The manuscript was not funded.

Declaration of financial/other relationships

H.O., A.G., M.M., M.D., R.S. and O.A.-R. have disclosed that they have no significant relationships with or financial interests in any commercial companies related to this study or article.

CMRO peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Acknowledgments

None reported.