ObjectiveAs more genes are incorporated into pharmacogenomic care processes and more importance is given to rare variants, the use of targeted capture sequencing panels has been proposed as a very efficient alternative due to their affordability, high throughput, and deep coverage, all of them characteristics of high-quality next-generation sequencing data. The purpose of this study is to describe the prevalence of clinically actionable pharmacogenetic variants previously described in the scientific literature, as well as that of new variants identified by next-generation sequencing technologies, and to evaluate the drugs potentially affected by such variants. MethodA panel of 18 clinically actionable pharmacogenomics-related genes was evaluated in 41 subjects diagnosed with breast cancer undergoing neoadjuvant treatment. The prevalence of previously described clinically actionable variants as well as of phenotypes classified according to current interpretation standards was studied. The pharmacological treatments potentially affected by the identified variants were also evaluated. An estimation was made of the prevalence of not previously described, possibly deleterious, variants selected using bioinformatics criteria. ResultsAll subjects carried clinically actionable variants, with a mean of 4.02 genes affected by each variant per individual. VKORC1, CYP4F2, CYP2C19, CYP2D6 and CYP2B6 were the most polymorphic genes and were present with actionable phenotypes in more than 50% of patients; 15-50% had actionable phonotypes in UGT1A1, SLCOIBI, CYP2C9 and TPMT and 2-15% in HLA-B, CYP3A5, HLA-A and DPYD. No actionable variants were identified in RYR1, CACNA1S, G6PD, F5 and NUDT15. These variants had the potential to affect response to 84% of the drugs described in the leading pharmacogenetic guidelines. Possibly deleterious variants not previously described accounted for 11.4% of all clinically actionable variants and were present in 12.2% of patients. ConclusionsThe results obtained show a high prevalence of clinically actionable variants, both common, i.e., previously described in the literature, and rare, i.e., not previously studied with conventional technological approaches. The latter are candidates for a more exhaustive molecular and/or clinical characterization.