Value of Molecular Classification for Prognostic Assessment of Adrenocortical Carcinoma

IMPORTANCE The risk stratification of adrenocortical carcinoma (ACC) based on tumor proliferation index and stage is limited. Adjuvant therapy after surgery is recommended for most patients. Pan-genomic studies have identified distinct molecular groups closely associated with outcome. OBJECTIVE To compare the molecular classification for prognostic assessment of ACC with other known prognostic factors. DESIGN, SETTING, AND PARTICIPANTS In this retrospective biomarker analysis, ACC tumor samples from 368 patients who had undergone surgical tumor removal were collected from March 1, 2005, to September 30, 2015 (144 in the training cohort and 224 in the validation cohort) at 21 referral centers with a median follow-up of 35 months (interquartile range, 18-74 months). Data were analyzed from March 2016 to March 2018. EXPOSURES Meta-analysis of pan-genomic studies (transcriptome,methylome, chromosome alteration, and mutational profiles) was performed on the training cohort. Targeted biomarker analysis, including targeted gene expression (BUB1B and PINK1), targeted methylation (PAX5, GSTP1, PYCARD, and PAX6), and targeted next-generation sequencing, was performed on the training and validation cohorts. MAIN OUTCOMES AND MEASURES Disease-free survival. Cox proportional hazards regression and C indexes were used to assess the prognostic value of each model. RESULTS Of the 368 patients (mean [SD] age, 49 [16] years), 144were in the training cohort (100 [69.4%] female) and 224were in the validation cohort (142 [63.4%] female). In the training cohort, pan-genomic measures classified ACC into 3 molecular groups (A1, A2, and A3-B), with 5-year survival of9%for group A1, 45%for group A2, and 82%for group A3-B (log-rank P < .001). Molecular classwas an independent prognostic factor of recurrence in stage I to III ACC after complete surgery (hazard ratio, 55.91; 95%CI, 8.55-365.40; P < .001). The combination of European Network for the Study of Adrenal Tumors (ENSAT) stage, tumor proliferation index, and molecular class provided the most discriminant prognostic model (C index, 0.88). In the validation cohort, the molecular classification, determined by targeted biomarker measures,was confirmed as an independent prognostic factor of recurrence (hazard ratio, 5.96 [95%CI, 1.81-19.58], P = .003 for the targeted classifier combining expression, methylation, and chromosome alterations; and 2.61 [95%CI, 1.31-5.19], P = .006 for the targeted classifier combiningmethylation, chromosome alterations, and mutational profile). The prognostic value of the molecular markerswas limited for patients with stage IV ACC. CONCLUSIONS AND RELEVANCE The findings suggest that in localized ACC, targeted classifiers may be used as independent markers of recurrence. The determination of molecular classmay improve individual prognostic assessment and thusmay spare unnecessary adjuvant treatment.