Deep sequencing across germline genome-wide association study signals relating to breast cancer events in women receiving aromatase inhibitors for adjuvant therapy of early breast cancer Objective To identify additional genetic variants beyond those observed in a previous genome-wide association study (GWAS) in women treated on the MA.27 clinical trial in which women were randomized to 5 years of adjuvant therapy with anastrozole or exemestane. Patients and methods We performed a matched case–control study in 234 women who had a recurrence of breast cancer (cases) and 649 women who had not (controls). The analysis was restricted to White women with an estrogen receptor-positive breast cancer. Multiplex PCR-based targeted deep sequencing was performed of the MIR2052HG region on chromosome 8 between positions 75.4 and 75.7, a span of 300 kb, in an attempt to identify additional functional single nucleotide polymorphisms (SNPs). Results A total of 4677 unique variants were identified that had not been identified in the previous GWAS. Clinical Annotation of Variants analysis revealed 10 variants, including eight SNPs and two insertion–deletion mutations with moderate or high impact. However, none of the common and variant regions was significant after adjustment for the most significant SNP (rs13260300) identified in our previous GWAS. We performed haplotype analysis that revealed two regions in which the haplotypes lost significance when adjusted for this prior GWAS SNP and one region with two significant haplotypes (P = 0.046 and 0.031) after adjusting for the GWAS SNP. Conclusion We were unable to identify common or rare variant regions that added value to the findings from our previous GWAS. We did find two haplotypes that were significant after adjusting for our top GWAS SNP but these were considered to be of marginal value.

Assessing the clinical impact of CYP2C9 pharmacogenetic variation on phenytoin prescribing practice and patient response in an integrated health system Objective To assess the impact of CYP2C9 variation on phenytoin patient response and clinician prescribing practice where genotype was unknown during treatment. Methods A retrospective analysis of Resource on Genetic Epidemiology Research on Adult Health and Aging cohort participants who filled a phenytoin prescription between 1996 and 2017. We used laboratory test results, medication dispensing records, and medical notes to identify associations of CYP2C9 genotype with phenytoin blood concentration, neurologic side effects, and medication dispensing patterns reflecting clinician prescribing practice and patient response. Results Among 993 participants, we identified 69% extensive, 20% high-intermediate, 10% low-intermediate, and 2% poor metabolizers based on CYP2C9 genotypes. Compared with extensive metabolizer genotype, low-intermediate/poor metabolizer genotype was associated with increased dose-adjusted phenytoin blood concentration [21.3 pg/mL, 95% confidence interval (CI): 13.6–29.0 pg/mL; P < 0.01] and increased risk of neurologic side effects (hazard ratio: 2.40, 95% CI: 1.24–4.64; P < 0.01). Decreased function CYP2C9 genotypes were associated with medication dispensing patterns indicating dose decrease, use of alternative anticonvulsants, and worse adherence, although these associations varied by treatment indication for phenytoin. Conclusion CYP2C9 variation was associated with clinically meaningful differences in clinician prescribing practice and patient response, with potential implications for healthcare utilization and treatment efficacy.

Association between HNF4A mutations and bleeding complications in patients with stable international normalized ratio Objectives This study aimed to determine the association between hepatocyte nuclear factor 4 alpha (HNF4A) polymorphisms and bleeding complications in patients on warfarin with international normalized ratios between 2.0 and 3.0 after cardiac valve replacement. Methods Nineteen single nucleotide polymorphisms of HNF4A in addition to VKORC1 rs9934438 and CYP2C9 rs1057910 were analyzed. Univariate and multivariate analyses were conducted to evaluate associations between genetic polymorphisms and bleeding risk. Attributable risk and number needed to genotype (NNG) were calculated to assess clinical value of genotyping. Results Of 142 patients, 21 experienced bleeding complications. Multivariate logistic regression analysis was conducted using factors with P <0.1 in univariate analysis. Multivariate analysis showed that patients with the CC genotype of rs6130615 had an 8.4-fold increased risk of bleeding, compared with patients with the T allele. Attributable risk and NNG were 88.1% and 32.2, respectively. Patients with the TT genotype of rs3212191 had a 3.8-fold increased risk of bleeding, compared with C allele carriers, while patients with variant-type homozygotes for rs1884613 showed an 8.7-fold higher bleeding complication than C allele carriers. The attributable risk/NNG of rs3212191 and rs1884613 were 73.4%/17.6 and 88.5%/22.8, respectively. Among comorbidities, atrial fibrillation was the only significant risk factor for bleeding complications. Conclusion Bleeding complications during warfarin therapy in patients with mechanical heart valves were associated with HNF4A polymorphisms and atrial fibrillation.