Efficacy of EDP±mitotane chemotherapy in the treatment of metastatic adrenocortical carcinoma. Predictive and prognostic factors of efficacy

Introduction. Adrenocortical carcinoma (ACC) is an orphan disease with an unfavorable prognosis. The most effective therapeutic option in the treatment of ACC is EDP plus mitotane combination chemotherapy. However, no studies comparing the efficacy of the EDP regimen with or without mitotane have been published. Materials and methods. A retrospective analysis of health records of patients with histologically confirmed metastatic ACC, who received at least one chemotherapy cycle with EDP ± mitotane. The study included 73 patients, 49 of which received a combination of EDP and mitotane and 24 were treated with EDP chemotherapy. Results. The objective response rate was 18,4 % in the EDP + mitotane group versus 4,1 % in the EDP group. Disease control was reported in 25 (51 %) and 13 (54,2 %) patients, respectively. No significant differences were found in progression-free survival (PFS) rates between the EDP and EDP + mitotane groups; the median PFS rate was 6,5 and 6,0 months, respectively. The median overall survival (OS) in the total population was 20,9 months; no significant differences were found between the groups. However, an increase in median PFS was observed in patients who achieved a therapeutic concentration of mitotane. Moreover, the achievement of therapeutic mitotane concentrations was the only factor significantly associated with improved PFS (HR 0.44, p = 0.006). Significant unfavorable prognostic factors associated with lower OS were Ki-67 level in the primary tumor > 20 % (HR 10.5, p = 0.006) and more than 1 site of metastases (HR 3.82, p = 0.02). Conclusions. This study showed that the addition of mitotane to EDP chemotherapy does not improve the median PFS and OS in the total patient population, however, the achievement of therapeutic mitotane concentrations is significantly associated with improved progression-free survival.