Abstract P3-06-01: Nuclear β-catenin negativity predicts for late relapse in ER+, tamoxifen-treated breast cancer
Authors: Hiscox Stephen , Smith Chris , Nicholson Robert I , Gee Julia , Harris Adrian , Bliss Judith , Kalaizak Eleftheria , Sestak Ivana , Dowsett Mitch , Cuzick Jack , Ellis Ian , Barrett-Lee Peter 
Published: May 2015

Abstract
Background: The annual recurrence rates of post-menopausal ER-positive breast cancers persist beyond the first 5 years of diagnosis and treatment and the mortality rates in this period are higher versus ER-negative cancers. Extended endocrine therapy past 5 years has been shown to be of benefit but is associated with increased toxicity and cost thus the ability to predict patients who are at highest risk of late relapse would be of significant benefit in clinical decision making in this context. β-catenin is an intracellular protein that undergoes Wnt-mediated nuclear translocation where it transactivates genes implicated in tumour development and progression. We have also previously reported that β-catenin can play a role in aggressive resistance that accompanies prolonged endocrine treatment in vitro. In this study, we thus investigated whether β-catenin expression in ER+ breast cancer was predictive of recurrence beyond 5 years in an analysis of three separate endocrine-treated cohorts.
Methods: Associations between β-catenin gene expression and relapse free survival (RFS) were performed using the online KMplotter tool. Immunostaining for total β-catenin was performed on tissue samples from 3 ER+ primary breast cancer series with long-term follow-up data: Nottingham 2000 (n=384, tamoxifen-only); ABC (n=570; tamoxifen only); transATAC (n=743; tamoxifen or ansatrozole). The association between subcellular (nuclear or cytoplasmic) β-catenin expression and RFS was determined in (i) the entire cohort, (ii) the first 5 years of tamoxifen treatment versus post-5 years.
Results: KMplotter analysis of β-catenin in ER+, tamoxifen-treated patient samples (n=665) revealed a significant relationship with improved RFS in the post-five year cohort [HR: 0.48 (0.34-0.68); p=0.000019) versus the first 5 years [HR: 0.91 (0.61-1.36; p=0.64)]. No significant association was observed in untreated ER+ patients. In the Nottingham series, nuclear β-catenin positivity was significantly associated with improved survival in the 20-year follow-up for tamoxifen-treated patients (p=0.047) but not in the first five years (p=0.239). Cytoplasmic β-catenin did not associate with survival. Further analysis in the ABC series revealed an association between nuclear β-catenin positivity and improved survival for tamoxifen-treated patients in the entire cohort (HR: 0.52 (0.18, 0.55); p=0.00005). However, nuclear β-catenin was more strongly associated with improved outcome in the post 5-year treatment group (HR: 0.30 (0.14, 0.66); p=0.01) versus the first five years of treatment (HR: 0.33 (0.15,0.73); p=0.06). No significant associations were seen with cytoplasmic β-catenin. The transATAC trial material again revealed an association between presence of nuclear β-catenin and reduced distant recurrence in the post 5-years endocrine-treated cohort (HR: 0.54 (0.33, 0.91): x2=5.52, p=0.018) versus years 1-5 (HR: 1.16 (0.67, 2.01); x2=0.29, p=0.59).
Conclusions: This is the first study to demonstrate that nuclear β-catenin may represent a predictive biomarker for late relapse following tamoxifen treatment in ER+ breast cancer where, contrary to traditional hypotheses and pre-clinical data, its nuclear expression is strongly associated with good outcome post-five years of treatment.
Citation Format: Stephen Hiscox, Chris Smith, Robert I Nicholson, Julia Gee, Adrian Harris, Judith Bliss, Eleftheria Kalaizak, Ivana Sestak, Mitch Dowsett, Jack Cuzick, Ian Ellis, Peter Barrett-Lee. Nuclear β-catenin negativity predicts for late relapse in ER+, tamoxifen-treated breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-06-01.