Copy number variants (CNVs) were identified and their relation to disease-free survival (DFS) was studied and validated in an independent cohort of 101 ASCC patients from the Multidisciplinary Spanish Digestive Cancer Group . Mitochondria and mitochondrial cell-cycle proteins were overexpressed in patients with CYP2D6 CNV . This study may be useful to suggest new treatment strategies to increase current therapy efficacy .