In a St. Jude Adrenocortical Tumor Registry and Children’s Oncology Group study reported in the Journal of Clinical Oncology, Pinto et al found that a positive Ki67 labeling index was associated with a poorer outcome in children with adrenocortical tumors independent of germline TP53 mutation status.
The study involved 42 female and 18 male pediatric patients from the St. Jude Children’s Research Hospital International Pediatric Adrenocortical Tumor Registry. Patients had a median age of 3.3 years (range = 0.25–21.7 years). Complete resection was accomplished in 32 patients with stage I and II disease, and 28 patients had stage III or IV disease. Genomic DNA was analyzed for TP53, CTNNB1, CDKN1C, ATRX, and chromosome 11p15 abnormalities, with β-catenin expression and Ki67 labeling index (positive = ≥ 15%) measured by immunostaining.
Factors Associated With Prognosis
Constitutional abnormalities of chromosome 11p15 were identified in 9 of 40 patients. Among all patients, progression-free survival at 3 years was 71.4%. In a single-predictor analysis, age, disease stage, tumor weight, somatic TP53 mutation (found in 9 of 54 patients), and Ki67 labeling index were significantly associated with prognosis. After adjustment for stage and tumor weight, Ki67 labeling index and age remained significantly associated with progression-free survival. Progression-free survival at 3 years was 48.5% among 27 patients with a Ki67 labeling index ≥ 15% vs 96.2% among 29 patients with a Ki67 labeling index < 15% (P = .002) The hazard ratio for relapse was 1.24 (P = .0057) for each 1-year increase in age at diagnosis.
The investigators concluded: “Our findings highlight the central role of genetic or epigenetic alterations on chromosome 11p15 in pediatric [adrenocortical tumors]. Ki67 [labeling index] is a strong prognostic indicator and should be investigated to improve the histologic classification of pediatric [adrenocortical tumors].”
The study was supported by the National Cancer Institute, the American Lebanese Syrian Associated Charities, and Centocor.
Raul C. Ribeiro, MD, of St. Jude Children’s Research Hospital, is the corresponding author of the Journal of Clinical Oncology article.
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