Local Recurrence after Breast-Conserving Therapy in Relation to Gene Expression Patterns in a Large Series of Patients

Abstract

Purpose: The majority of patients with early-stage breast cancer are treated with breastconserving therapy (BCT). Several clinical risk factors are associated with local recurrence (LR) after BCT but are unable to explain all instances of LR after BCT. Here, gene expression microarrays are used to identify novel risk factors for LR after BCT. Experimental Design: Gene expression profiles of 56 primary invasive breast carcinomas from patients who developed a LR after BCT were compared with profiles of 109 tumors from patients who did not develop a LR after BCT. Both unsupervised and supervised methods of classification were used to separate patients into groups corresponding to disease outcome. In addition, for 15 patients, the gene expression profile in the recurrence was compared with that of the primary tumor. Results: The two main clusters found by hierarchical cluster analysis of all 165 primary invasive breast carcinomas revealed no association with LR. Predefined gene sets (molecular subtypes and "chromosomal instability" signature) are associated with LR (P = 0.0002 and 0.003, respectively). Significant analysis of microarrays revealed an association between LR and cell proliferation, not captured by histologic grading. Class prediction analysis constructed a gene classifier, which was successfully validated, cross-platform, on an independent data set of 161 patients (log-rank P = 0.041). In multivariate analysis, young age was the only independent predictor of LR. Conclusions: We have constructed and cross-platform validated a gene expression profile predictive for LR after BCT, which is characterized by genes involved in cell proliferation but not a surrogate for high histologic grade.Local treatment for early-stage breast cancer can consist of mastectomy or breast-conserving therapy (BCT). Several randomized controlled trials have shown no difference in survival rates after BCT or mastectomy for stage I and II breast cancer (1-3). Unfortunately, BCT is associated with a higher rate of local recurrence (LR) compared with mastectomy (1-3). A LR rate of <1% per annum is generally considered as clinically acceptable for T1-2 N0-1 breast cancers. The choice for the primary treatment modality is therefore often based on risk factors for LR.Several of these risk factors for LR after BCT have been identified: involvement of the surgical margins by invasive carcinoma [hazard ratio (HR), 2.8-3.9] and/or extensive ductal carcinoma in situ (DCIS; HR, 2.5-4.2), vascular invasion (HR, 2.0-2.9), young age (HR, 2.4-9.2), and tumor multicentricity (HR,. The addition of a radiation boost after whole-breast irradiation and adjuvant systemic therapy reduces LR rates by 40% to 60%, especially in younger patients (9,11,16,17,19,20).The importance of preventing LR is illustrated by the updated analyses of the Early Breast Cancer Trialists' Collaborative Group showing that LR is associated with poorer survival (21) and by Voogd et al. (22) who suggest that early detection of LR could improve survival. Thus, robust r...

Development and Validation of a Gene Profile Predicting Benefit of Postmastectomy Radiotherapy in Patients with High-Risk Breast Cancer: A Study of Gene Expression in the DBCG82bc Cohort

“…[33][34][35][36] and after mastectomy (37) have been published previously, but none of them have been successfully validated. The study by Cheng and colleagues (37) identified 34 genes with significant association with LRR.…”

“…Nuyten and colleagues (33) and Kreike and colleagues (40) did not identify a specific geneset predicting risk of recurrence after BCT, though a gene profile based on the wound response signature was described as being of independent prognostic value. Later, the same group developed a 111-gene signature (35), but it did not show independent prognostic value in multivariate analysis, and lost prognostic impact when tested in independent cohorts (34,41 Time after treatment (years) identify patients developing LRR despite radiotherapy after BCT, could not be validated in other cohorts (35,36,41), and the most recent study by Sabatier and colleagues (36) did not succeed in determining a robust prognostic signature of LRR.…”

Search for a Gene Expression Signature of Breast Cancer Local Recurrence in Young Women

“…The fact that (young) age is the single most important risk factor, independent of all others (5), suggests that some unrevealed biologic characteristics of the primary breast cancer may be associated with a higher risk of developing a true local recurrence, that is, regrowth of clonogenic cells that were not removed by surgery or killed by radiotherapy (6). Gene expression profiling of primary breast carcinomas using microarray technology has already been used to try and discover a signature associated with a higher risk of developing true recurrence after BCT (7)(8)(9)(10). Results have been contradictory.…”

“…The most recent and largest study, by Kreike and colleagues (10), is for a series of 165 young ( 50 years old) premenopausal Dutch patients using the Human Genome Oligo Set version 3.0 array (Operon) and did not confirm previous classifiers, namely, those based on the wound response signature (8) and that defined by Nim eus-Malmstr€ om and colleagues (9). Kreike and colleagues were able to construct a local recurrence classifier based on the expression of 111 genes and validate this profile on an independent data set of 161 consecutive patients with breast cancer treated by BCT who used a different microarray platform (10). This classifier was mostly characterized by proliferation but did not bring a significant independent additive value, as young age remained the sole predictive factor of local recurrence in multivariate analysis.…”

High expression stability of microtubule affinity regulating kinase 3 (MARK3) makes it a reliable reference gene

“…In the recent years, experiments related to gene studies (1)(2)(3)(4)(5)(6) often require the usage of reference genes-genes that are constitutively and constantly expressed in different environmental conditions (7)(8)(9). Housekeeping genes, which are essential for the maintenance of the cell, are generally assumed to be stably expressed (10).…”