Abstract P1-05-03: Predictive value of de novo and induced epithelial-mesenchymal transition in locally advanced breast cancer treated with neoadjuvant chemotherapy
Authors: Redfern AD , McLaren SA , Dissanayake V , Chan A , Zeps N , Dobrovic A , Soon L , Thompson EW , Christobel SM 
Published: May 2016

The dynamic transformation of an adherent proliferative epithelial cell to a migratory and invasive mesenchymal state that can drive tumour metastasis has been widely acknowledged in in vitro models as epithelial-mesenchymal transition (EMT). We have characterized EMT status in tissues from 35 locally advanced breast cancer (LABC) patients before and after receiving anthracycline and taxane-based neoadjuvant chemotherapy (NAC). Routine analyses for ER, PR, HER2, lymphovascular invasion (LVI) and tumour staging parameters were available for all patients and five year recurrence and survival data was available for 34. Six patients (17%) had a pathological complete response (pCR), five of whom were hormone receptor (HR) negative and one HR positive. 11 patients (43%) had had disease recurrence and 10 (40%) had died from breast cancer at five years follow up.

Core biopsy tissue specimens were available prior to NAC from all 35 patients. Resected tissue following NAC was available from 17 cases with residual disease. Tissue sections were stained for the epithelial marker cytokeratin 19 (CK19) and the mesenchymal marker vimentin (VIM). Fluorescent, multi-channel microscopy identified co-localization of CK19 and VIM within tumour cells, indicating the presence of EMT.

Evidence of EMT prior to NAC was seen in 14/35 (40%) of LABC cases. There was no association between EMT status pre-NAC and pCR which was observed in 2/14 EMT positive and 4/21 EMT negative patients. However, in patients with detectable EMT pre-NAC there was significantly improved five year disease-free survival (86 vs. 52%, p=0.04) and a trend to improved five year overall survival (86 vs. 62%, p=0.12) compared to cases that were EMT negative pre-NAC.

Of the 17 cases without a pCR with tissue available for assessment of pre- and post-NAC EMT status, seven had disease recurrence and six died by five years. Four cases that were EMT negative pre-NAC developed EMT positive tumour cells following NAC, and all have subsequently developed metastatic disease and died from breast cancer. Two cases lost detectable EMT after chemotherapy, both of whom remain alive. In contrast to pre-NAC EMT, induction of EMT following NAC was associated with trends to worse five year disease-free and overall survival (45 v 75%, p=0.20) and (56 v 75%, p=0.40). Additionally, when events past five years are included in analysis, detectable EMT in the post-NAC tissue sample (induced and retained) correlated with a trend to increased recurrence (p=0.09) and to a statistically significant increase in overall mortality (p=0.04).

This is the first study to explore EMT induction and loss during NAC in the clinical setting. Although patient numbers are few, the data show EMT induction during chemotherapy in a moderate proportion of cases. Observations of significantly superior five year disease free survival in patients without detectable EMT pre-NAC and significantly inferior overall survival in those with visible EMT post-NAC need to be interpreted with caution. Larger studies are needed to further examine this potential prognostic differential between EMT detectable either before or after NAC, and to explore how this may guide therapy.

Citation Format: Redfern AD, McLaren SA, Dissanayake V, Chan A, Zeps N, Dobrovic A, Soon L, Thompson EW, Christobel SM. Predictive value of de novo and induced epithelial-mesenchymal transition in locally advanced breast cancer treated with neoadjuvant chemotherapy. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-05-03.