Abstract 433P
Background
Presence of extramural venous invasion (EMVI) by magnetic resonance imaging (MRI) is an independent poor prognostic factor in locally advanced rectal cancer (LARC). Nevertheless, the efficacy of both pre-neoadjuvant therapy (NAT) and post-NAT MRI EMVI assessment to predict pathological response and long-term benefit (in terms of disease-free survival (DFS) and overall survival (OS) has not been clearly established.
Methods
We analyzed 239 patients with LARC receiving NAT with continuous infusion fluorouracil (n=229) or capecitabine (n=10) diagnosed between 2009 and 2019. Baseline and post-NAT MRI EMVI status was assessed in 214 and 173 patients respectively by two radiologists with more than 20-year and 5-year experience. When discrepancies, EMVI status was decided by consensus. Post-surgical pathologic assessment detached good-responders (ypT0N0 and ypT1-2N0) from poor-responders (ypT3Nx or ypTxN1/2). Three-year DFS and 5-year OS were estimated using Kaplan-Meier product-limit method.
Results
Baseline EMVI positive (91/214; 42%) was significantly associated with poor pathological response (74/91; 81%) vs. EMVI negative (52/123; 43%), p=0.0001. In the subset of patients evaluated with pre and post MRI, 69/173 (40%) presented positive EMVI at baseline. 21/69 (30%) patients with positive baseline EMVI became negative after therapy (EMVI (+/-)). Three-year DFS was 80.9% in EMVI (-/-), 66.7% in EMVI (+/-), and 45.2% in EMVI (+/+), HR 1.84 (95% CI 1.38-2.44), p=0.000026. Five-year OS was 82.6%, 73.9% and 57.3%, respectively, with HR 1.67 (95% CI 1.26-2.23), p=0.0004.
Conclusions
Baseline EMVI accurately predicted pathological efficacy after conventional NAT. Patients that negativized EMVI (+/-) showed significantly better DFS and OS compared to patients that remained positive EMVI (+/+).
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
J. Maurel: Non-Financial Interests, Institutional, Advisory Role: Sitex Medical, Pierre Fabre, AstraZeneca, Servier, Sanofi; Non-Financial Interests, Institutional, Advisory Board: Shire; Financial Interests, Institutional, Research Grant: Merck Serono, Amgen, NanoString Technologies, Biocartis, Roche, Incyte; Financial Interests, Institutional, Other: Amgen. All other authors have declared no conflicts of interest.