Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2018

Prognostic utility of CDX2 and PD-L1 in Rectal Cancer (#317)

Adel Shahnam 1 , Elizabeth Paver 1 , Bella Nguyen 1 , Mitali N Fadia 1 , Sayed Ali 1
  1. The Canberra Hospital, Garran, AUSTRALIAN CAPITAL TERRITORY, Australia

Introduction: The only definitive indication for neoadjuvant treatment for locally advanced rectal adenocarcinoma remains the presence of T3/T4 tumour radiographically, and there is no other available prognostic biomarkers for risk stratification. Recently the two biomarkers, caudal type homeobox transcription factor 2 (CDX2) and programmed cell death ligand 1 (PD-L1), have shown to have predictive and prognostic influence on response and survival in a number of solid tumours. There are no adequate published reports on the incidence of CDX2 and PD-L1 expression in rectal cancer patients receiving neoadjuvant therapy thus the clinical generalizability of these biomarkers remains unknown


Aims: In a pilot study, we set out to investigate the incidence of CDX2 and PDL-1 expression in rectal cancer patients.


Methods: A retrospective analysis of 60 patients diagnosed with rectal cancer, who received neoadjuvant chemoradiotherapy treatment between 2005-2016 at The Canberra Hospital was performed. Immunohistochemistry stains using CDX2 and VENTANA rabbit monoclonal primary PD-L1 antibody (clone SP263) were performed on paraffin blocks using an autostainer on patients pre- and post- treatment histological samples.


Results: The median age at diagnosis of our sample was 65 years (68.3% males (n=41) with 83.3% (n=50) having cT3 or cT4 tumor, classified on pre-treatment imagings. We found that there were no negative experessor of CDX2 within our patient sample. In terms of PD-L1, 1 patient was positive in the pre-treatment histological sample whilst 3 patients had positive expressions in the post-treatment sample (2 acquired positive expression compared to pre-treatment sample)


Conclusion: Further research is required to investigate the incidence of CDX2 and PD-L1 expression in rectal cancer and to determine the prognostic utility of these biomarkers to enable stratification of patients into risk groups to aid therapeutic decision-making.