Evaluation of RRP1B polymorphisms in relation to tumor biology and survival outcomes in early-stage breast cancer

Background and Objectives Breast cancer (BC) is a heterogenous disease characterized by substantial variability in tumor biology and clinical behavior. This heterogeneity is reflected in clinicopathological features, including hormone receptor status, human epidermal growth factor receptor 2 (HER2) expression, tumor histological grade, tumor size, and disease stage, which describe tumor features and are key determinants of prognosis. Single nucleotide polymorphisms (SNPs) have been proposed as potential contributors to inter-individual differences in these tumor features and clinical outcomes; however, their role in early-stage BC remains insufficiently defined. In this study, polymorphisms in the RRP1B gene, specifically rs2838342 and rs2051407, were investigated for their potential associations with BC features and outcomes. Material and Method Study population. A total of 191 adult female patients with primary stage I-II BC were enrolled. All participants provided written informed consent, and the study was approved by the Kaunas Regional Ethics Committee for Biomedical Research (nos. BE-2-10 and P1-BE-2-10/2014). Peripheral blood samples were collected for genetic analysis. DNA extraction and genotyping. Genomic DNA was extracted from peripheral blood using a spin column-based extraction method with a commercially available kit. SNP genotyping was performed using TaqMan allelic discrimination assays on a Quanstudio 3 Real-Time PCR System. Statistical analysis. Associations between SNPs and clinicopathological features as well as binary clinical outcomes (disease progression, metastasis status, and mortality status) were evaluated using logistic regression under an additive genetic model. Both univariate and age-adjusted multivariable analyses were performed. Sensitivity analyses using alternative genetic models were conducted for selected SNPoutcome associations showing non-linear patterns in genotype distributions. Progression-free, overall, and metastasis-free survival (MFS) were analyzed using Kaplan-Meier with log-rank tests and Cox proportional hazards regression models under an additive genetic model. Multivariable Cox models were adjusted for established clinicopathological prognostic factors. To account for multiple testing, the Benjamini-Hochberg false discovery rate (FDR) correction was applied separately for clinicopathological features (n = 12), binary clinical outcomes (n = 6), and Cox models (n = 6), using p-values from fully adjusted additive models. Kaplan-Meier analyses were considered descriptive and were not included in correction. Adjusted p-values (q-values) < 0.05 were considered significant. All statistical analyses were performed using IBM SPSS Statistics 30.0.0.0. Results Genotype distributions were as follows: for rs2838342, AA 30.9% (n = 59), AG 51.8%, (n = 99), and GG 17.3% (n = 33); for rs2051407, CC 36.6% (n = 70), CT 45.5 % (n = 87), and TT 17.8% (n = 34). The minor allele frequencies were 43.2% for rs2838342 and 40.6% for rs2051407. Genotype frequencies for both SNPs were consistent with Hardy-Weinberg equilibrium (p > 0.05). In age-adjusted additive logistic regression models, rs2838342 was associated with tumor size (p = 0.022) and histological grade (p = 0.032), although neither association remained significant after correction for multiple testing. Under a recessive genetic model, rs2838342 was associated with estrogen receptor (ER) status after adjustment for age group (OR = 0.38, 95% CI 0.17-0.85, p = 0.018), suggesting a lower likelihood of ER positivity among GG homozygotes. A similar nonsignificant trend under the same genetic model was observed for rs2051407 (p = 0.072). Kaplan-Meier analyses showed no statistically significant differences in survival outcomes across genotype groups. Consistently, no associations were observed in Cox regression analyses under unadjusted or multivariable-adjusted models accounting for age and clinicopathological variables. All results remained non-significant after Benjamini-Hochberg FDR correction. Conclusions and Recommendations No statistically significant associations were observed between the studied SNPs and clinicopathological or survival outcomes after multiple testing correction. However, nominal and model-specific associations for rs2838342 indicate a potential role in tumor biology requiring validation in larger, independent cohorts.