Assessment of the AJCC staging system of pheochromocytomas/paragangliomas

This study aims to assess the performance of the AJCC 8th staging system for pheochromocytomas and paragangliomas (PPGLs) based on a population-based cohort.

Surveillance, epidemiology, and end results (SEER)-18 registry database was reviewed, and patients with PPGLs diagnosed 2004-2015 were reviewed. AJCC stage for each patient was reconstructed from the collaborative stage dataset. Kaplan-Meier survival estimates according to the AJCC stage were reviewed, and multivariable Cox regression analysis was conducted to determine the impact of AJCC stages on overall and cancer-specific survival.

A total of 416 patients with PPGLs were eligible and were included in the current analysis. Using Kaplan-Meier survival estimates, patients with stage IV seem to have the worst overall survival (P < 0.001). When the results were stratified by the site of origin (adrenal vs. extra-adrenal), similar findings were observed in both strata (P < 0.001 in each stratum). Using multivariable Cox regression analysis for overall survival, HR for stage I vs. II was: 0.59; (95% CI: 0.27-1.27), HR for stage II vs. III: 0.82; (95% CI: 0.41-1.63), and HR for stage III vs. IV was: 0.37; (95% CI: 0.24-0.58). Likewise, for cancer-specific survival, HR for stage I vs. II was: 0.72; (95% CI: 0.26-1.97), HR for stage II vs. III: 0.64; (95% CI: 0.25-1.63), and HR for stage III vs. IV was: 0.33; (95% CI: 0.19-0.56). C-statistic for AJCC 8th staging system was: 0.723 (95% CI: 0.669-0.776).

Further improvements within AJCC 8th edition are possible, including the inclusion of the extent of metastatic disease in the subclassification of stage IV disease, and not considering primary tumor site when assigning T stage.