Post-Therapy Fibrosis As A Surrogate Of Original Tumor Bulk In Locally Advanced Rectal Cancer (Lara): An Exploratory Study Of Radiographic Mis-Staging And Inflation Of Therapeutic Benefit

e14551 Background: Delivery of neoadjuvant chemoradiotherapy (NACRT) in LARA is predicated on MRI staging. Small series of direct-to-surgery patients (pts) suggested high rates of over/under-staging of pts. Tumour bed fibrosis reflects the extent of NACRT response and could be used as a surrogate of pre-therapy tumour stage. Comparing to fibrosis-based staging, we sought to examine 1.) rates of staging discrepancy and 2.) true magnitude of response to NACRT. Methods: Consecutive pts with diagnosis of LARA who received NACRT were identified from institutional database between January 2011 and November 2013. Demographics and clinical stages were extracted from health records. Histopathology reports were reviewed to obtain post-NACRT staging and to estimate pre-therapy staging based on extent of fibrosis according to AJCC 7th edition. Results: 60 pts were identified with a median age of 66 years (range: 27 – 85), of which 42 (70%) were males. Distribution of clinical, fibrosis-based, and post-therapy T- and ...