Background:Clinical outcome of adrenocortical carcinoma(ACC)varies because of its heterogeneous nature and reliable prognostic prediction model for adult ACC patients is limited.The objective of this study was to develop and externally validate a nomogram for overall survival(OS)prediction in adult patients with ACC after surgery.Methods:Based on the data from the Surveillance Epidemiology,and End Results(SEER)database,adults patients diagnosed with ACC between January 1988 and December 2015 were identified and classified into a training set,comprised of 404 patients diagnosed between January 2007 and December 2015,and an internal validation set,com-prised of 318 patients diagnosed between January 1988 and December 2006.The endpoint of this study was OS.The nomogram was developed using a multivariate Cox proportional hazards regression algorithm in the training set and its performance was evaluated in terms of its discriminative ability,calibration,and clinical usefulness.The nomogram was then validated using the internal SEER validation,also externally validated using the Cancer Genome Atlas set(TCGA,82 patients diagnosed between 1998 and 2012)and a Chinese multicenter cohort dataset(82 patients diag-nosed between December 2002 and May 2018),respectively.Results:Age at diagnosis,T stage,N stage,and M stage were identified as independent predictors for OS.A nomo-gram incorporating these four predictors was constructed using the training set and demonstrated good calibration and discrimination(C-index 95%confidence interval[CI],0.715[0.679-0.751]),which was validated in the internal validation set(C-index[95%CI],0.672[0.637-0.707]),the TCGA set(C-index[95%CI],0.810[0.732-0.888])and the Chi-nese multicenter set(C-index[95%CI],0.726[0.633-0.819]),respectively.Encouragingly,the nomogram was able to successfully distinguished patients with a high-risk of mortality in all enrolled patients and in the subgroup analyses.Decision curve analysis indicated that the nomogram was clinically useful and applicable.Conclusions:T
