Revisiting the AJCC staging system of adrenocortical carcinoma.

OBJECTIVE

To evaluate the performance characteristics of AJCC 7th and 8th staging systems among patients with adrenal cortical carcinoma.

METHODS

Surveillance, Epidemiology, and End Results (SEER) 18-registry was accessed and patients with adrenocortical carcinoma who were diagnosed 2010-2015 with complete information about AJCC 7th staging system were included. AJCC 8th staging system information was then reconstructed for each patient using available TNM staging variables. Kaplan-Meier overall survival estimates, multivariable Cox regression analysis, and concordance index (C-statistic) were used to examine the performance characteristics of both staging systems.

RESULTS

A total of 574 patients with a diagnosis of adrenocortical carcinoma were included in the current analysis. Using Kaplan-Meier survival estimates, overall survival was compared among different AJCC stages for both versions; and the P value was significant (< 0.001) for both comparisons. C-statistic was then calculated for both staging systems and the results were as follows: for AJCC 7th version: 0.726 (95% CI 0.683-0.769); and for AJCC 8th version: 0.745 (95% CI 0.704-0.786). Patients with M1 disease (stage IV according to AJCC 8th edition) were then divided according to the extent of distant metastases into single versus multiple sites of metastases. Using Kaplan-Meier survival estimates, patients with a single site of metastases have better overall survival (P = 0.006). A C-statistic for a hypothetical modification of AJCC 8th staging system subdividing stage IV patients into IVA and IVB based on the number of metastatic sites was: 0.753 (95% CI 0.713-0.794).

CONCLUSIONS

There is a minimal difference in the prognostic performance between both versions of the AJCC staging system. Subdivision of stage IV cancer into stage IVA and IVB (according to the number of organs with metastatic deposits) should be considered in subsequent versions of adrenocortical carcinoma staging.