Fig. 1

Flowchart of the study. a The study population included a total of 224 patients with solid cancers treated with fluoropyrimidine (FL)-based therapy divided into cases (“toxicity group”) and controls (“no-toxicity group”). b Blood-derived DNA from cases and controls was genotyped using a customized targeted next-generation sequencing panel comprising 54 genes. c Raw sequencing data were processed through a data analysis pipeline that allowed identification/annotation of germline genetic variants. Variant classification based on minor allele frequency (MAF, common ≥ 1% and rare < 1%) and functional annotation of variants were also performed. d Variant analysis was performed using the Sequence Kernel Association Test (SKAT) for common and rare variants combined (SKATjoint). Variants were grouped at the gene and subpathway levels. These analyses allowed identification of candidate genes associated with risk of severe FL-related toxicity. e The predictive role of common or rare variants in the selected candidate genes for the risk of developing severe FL-related toxicity was further investigated. *MAF-based variant classification: very rare, MAF ≤ 0.1%; rare, 0.1% < MAF < 1%; common, MAF ≥ 1%; novel, MAF not registered + no rs ID. In SKAT analysis, very rare and novel variants are included in the rare group