Development and internal validation of an adrenal cortical carcinoma prognostic score for predicting the risk of metastasis and local recurrence

Objective To develop and internally validate a prognostic score to predict the risk of metastases or recurrence in patients with adrenal cortical carcinomas (ACC). Design Clinical, laboratory and pathological data from 129 ACC patients, treated in a tertiary centre, were retrospectively reviewed. Results Using a multivariate binary logistic regression analysis, we developed a prognostic score with five covariates: a functional pattern other than isolated hyperandrogenism, a tumour size >75cm, a primary tumour classified as T3/T4, the presence of microscopic venous invasion and a mitotic index >5/50 high-power fields. The prognostic score was calibrated according to the Hosmer-Lemeshow goodness-of-fit test (P=09329) and exhibited excellent overall performance (Brier score=00738). Finally, the discriminatory ability of the model, determined by the area under the ROC curve (A(ROC)), was near perfect (A(ROC), 09611; 95% CI, 092676-099552). The prediction model was internally validated with 200 bootstrap resamples and achieved excellent performance for estimating the risk of metastasis and recurrence in eight additional patients with apparently localized disease at diagnosis. Conclusion We developed and internally validated a prognostic score based on the clinicopathological data that are readily available to any attending physician. Our model can be used to accurately estimate the risk of unfavourable outcomes in ACC patients. This score could be beneficial for both patient counselling and the identification of patients in whom adjuvant mitotane is justified.