Flockhart, David A.

Purpose No biomarkers have been identified to predict outcome with the use of an antiangiogenesis agent for cancer. Vascular endothelial growth factor (VEGF) genetic variability has been associated with altered risk of breast cancer and variable promoter activity. Therefore, we evaluated the association of VEGF genotype with efficacy and toxicity in E2100, a phase III study comparing paclitaxel versus paclitaxel plus bevacizumab as initial chemotherapy for metastatic breast cancer. Patients and Methods DNA was extracted from tumor blocks of patients from E2100. Three hundred sixty-three samples were available to evaluate associations between genotype and outcome. Genotyping was performed for selected polymorphisms in VEGF and VEGF receptor 2. Testing for associations between each polymorphism and efficacy and toxicity was performed. Results The VEGF-2578 AA genotype was associated with a superior median overall survival (OS) in the combination arm when compared with the alternate genotypes combined (hazard ratio = 0.58; 95% CI, 0.36 to 0.93; P = .023). The VEGF-1154 A allele also demonstrated a superior median OS with an additive effect of each active allele in the combination arm but not the control arm (hazard ratio = 0.62; 95% CI, 0.46 to 0.83; P = .001). Two additional genotypes, VEGF-634 CC and VEGF-1498 TT, were associated with significantly less grade 3 or 4 hypertension in the combination arm when compared with the alternate genotypes combined (P = .005 and P = .022, respectively). Conclusion Our data support an association between VEGF genotype and median OS as well as grade 3 or 4 hypertension when using bevacizumab in metastatic breast cancer.

Abstract Purpose: Genetic variation in cytochrome P450 2D6 (CYP2D6) and the gene expression ratio of the homeobox 13 (HOXB13) to interleukin-17B receptor (IL17BR) are associated with tamoxifen resistance. We sought to determine the combined effect of inherited (CYP2D6) and somatic (HOXB13/IL17BR) gene variation in tamoxifen-treated breast cancer. Experimental Design: Retrospective analysis of women with node-negative breast cancer randomized to receive 5 years of tamoxifen (North Central Cancer Treatment Group 89-30-52). CYP2D6 metabolism (extensive or decreased) was based on CYP2D6*4 genotype and presence/absence of a CYP2D6 inhibitor. Reverse transcription-PCR profiles for HOXB13 and IL17BR and the cut point separating patients into high- and low-risk categories according to disease-free survival (DFS) were used. A risk factor (CYP2D6:HOXB13/IL17BR) representing the four categories of combining CYP2D6 metabolism (extensive or decreased) and HOXB13/IL17BR (low or high) was created. The association between CYP2D6:HOXB13/IL17BR and DFS and overall survival (OS) was assessed using the log-rank test and proportional hazards modeling. Results: CYP2D6 metabolism and HOXB13/IL17BR gene ratio was available in 110 of 160 (69%) patients. The combined CYP2D6:HOXB13/IL17BR risk factor was significantly associated with DFS (log-rank P = 0.004) and OS (P = 0.009). Relative to women with extensive CYP2D6 metabolism and low HOXB13/IL17BR, those with either decreased metabolism or a high HOXB13/IL17BR ratio had significantly worse OS (adjusted hazard ratio, 2.41; 95% confidence interval, 1.08-5.37; P = 0.031), whereas women with both decreased metabolism and high HOXB13/IL17BR ratio had the shortest survival (adjusted hazard ratio, 3.15; 95% CI, 1.17-8.52; P = 0.024). Conclusions: An index composed of inherited (CYP2D6) and tumor (HOXB13/IL17BR) gene variation identifies patients with varying degrees of resistance to tamoxifen.

Purpose Polymorphisms in tamoxifen metabolizing genes affect the plasma concentration of tamoxifen metabolites, but their effect on clinical outcome is unknown. Methods We determined cytochrome P450 (CYP)2D6 (*4 and *6) and CYP3A5 (*3) genotype from paraffin-embedded tumor samples and buccal cells (living patients) in tamoxifen-treated women enrolled onto a North Central Cancer Treatment Group adjuvant breast cancer trial. The relationship between genotype and disease outcome was determined using the log-rank test and Cox proportional hazards modeling. Results Paraffin blocks were obtained from 223 of 256 eligible patients, and buccal cells were obtained from 17 living women. CYP2D6 (*4 and *6) and CYP3A5 (*3) genotypes were determined from 190, 194, and 205 patient samples and in 17 living women. The concordance rate between buccal and tumor genotype was 100%. Women with the CYP2D6 *4/*4 genotype had worse relapse-free time (RF-time; P = .023) and disease-free survival (DFS; P = .012), but not overall survival (P = .169) and did not experience moderate to severe hot flashes relative to women heterozygous or homozygous for the wild-type allele. In the multivariate analysis, women with the CYP2D6 *4/*4 genotype still tended to have worse RFS (hazard ratio [HR], 1.85; P = .176) and DFS (HR, 1.86; P = .089). The CYP3A5*3 variant was not associated with any of these clinical outcomes. Conclusion In tamoxifen-treated patients, women with the CYP2D6 *4/*4 genotype tend to have a higher risk of disease relapse and a lower incidence of hot flashes, which is consistent with our previous observation that CYP2D6 is responsible for the metabolic activation of tamoxifen to endoxifen.