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PURPOSE: Local recurrence and distant failure after adjuvant radiation therapy for breast cancer remain significant clinical problems, incompletely predicted by conventional clinicopathologic markers. We had previously identified microRNA-139-5p and microRNA-1274a as key regulators of breast cancer radiation response in vitro. The purpose of this study was to investigate standard clinicopathologic markers of local recurrence in a contemporary series and to establish whether putative target genes of microRNAs involved in DNA repair and cell cycle control could better predict radiation therapy response in vivo. METHODS AND MATERIALS: With institutional ethics board approval, local recurrence was measured in a contemporary, prospectively collected series of 458 patients treated with radiation therapy after breast-conserving surgery. Additionally, independent publicly available mRNA/microRNA microarray expression datasets totaling >1000 early-stage breast cancer patients, treated with adjuvant radiation therapy, with >10 years of follow-up, were analyzed. The expression of putative microRNA target biomarkers--TOP2A, POLQ, RAD54L, SKP2, PLK2, and RAG1--were correlated with standard clinicopathologic variables using 2-sided nonparametric tests, and to local/distant relapse and survival using Kaplan-Meier and Cox regression analysis. RESULTS: We found a low rate of isolated local recurrence (1.95%) in our modern series, and that few clinicopathologic variables (such as lymphovascular invasion) were significantly predictive. In multiple independent datasets (n>1000), however, high expression of RAD54L, TOP2A, POLQ, and SKP2 significantly correlated with local recurrence, survival, or both in univariate and multivariate analyses (P<.001). Low RAG1 expression significantly correlated with local recurrence (multivariate, P=.008). Additionally, RAD54L, SKP2, and PLK2 may be predictive, being prognostic in radiation therapy-treated patients but not in untreated matched control individuals (n=107; P<.05). CONCLUSIONS: Biomarkers of DNA repair and cell cycle control can identify patients at high risk of treatment failure in those receiving radiation therapy for early breast cancer in independent cohorts. These should be further investigated prospectively, especially TOP2A and SKP2, for which targeted therapies are available.

Original publication

DOI

10.1016/j.ijrobp.2015.08.046

Type

Journal article

Journal

Int j radiat oncol biol phys

Publication Date

01/12/2015

Volume

93

Pages

1104 - 1114

Keywords

Adult, Aged, Aged, 80 and over, Antigens, Neoplasm, Antineoplastic Agents, Hormonal, Breast Neoplasms, Case-Control Studies, DNA Helicases, DNA Repair, DNA Topoisomerases, Type II, DNA-Binding Proteins, DNA-Directed DNA Polymerase, Female, Gene Expression Profiling, Genes, cdc, Genetic Markers, Homeodomain Proteins, Humans, MicroRNAs, Middle Aged, Multivariate Analysis, Neoplasm Recurrence, Local, Nuclear Proteins, Poly-ADP-Ribose Binding Proteins, Prospective Studies, Radiation Tolerance, Radiotherapy, Adjuvant, S-Phase Kinase-Associated Proteins