Statistical Tests Used to Validate the American Joint Committee on Cancer Eighth Edition Prognostic Stage Compared With the Anatomic Stage in Breast Cancer

To the Editor Weiss et al¹ validated the American Joint Committee on Cancer Eighth Edition prognostic stage and compared it with the anatomic stage in breast cancer in 2 large cohorts. The authors used the Harrell C index to qualify the models’ predictive performance based on prognostic stage and anatomic stage, respectively. The authors further determined the significance between the Harrell C index of the prognostic stage and anatomic stage using the R package compareC. In the MD Anderson cohort, the Harrell C indices for the prognostic stage and the anatomic stage are 0.8357 and 0.7370 (P < .001). In the California Cancer Registry, the Harrell C indices for the prognostic stage and the anatomic stage are 0.8426 and 0.8097 (P < .001).