Impact of perineural and lymphovascular invasion on oncological outcomes in rectal cancer treated with neoadjuvant chemoradiotherapy and surgery.

695 Background: The prognostic significance of perineural and/or lymphovascular invasion (PLVI) and its relationship with tumor regression grade (TRG) in patients with locally advanced rectal cancer (LARC) treated with neoadjuvant chemoradiotherapy (CRT) and surgery. Methods: A total of 324 patients with LARC treated with CRT were operated on between January 1992 and June 2007. Tumors were graded using a quantitative 5-grade TRG classification, and the presence of PLVI was studied histologically. Results: At a median follow-up of 79.0 months (range 3–250 months), a total of 80 patients (24.7%) relapsed. The observed 5- and 10-year overall survival (OS) was 83.2% and 74.9% respectively. The 5- and 10-year disease-free survival (DFS) was 75.1% and 71.4%, respectively. A significant correlation was found between the TRG and survival (log rank, p<0.001). The 10-year OS and DFS was 32.7% and 31.8% for grade 1; 63.8% and 58.6% for grade 2; 75.0% and 70.4% for grade 3; 90.4% and 88.4% for grade 3+, and 96.0% and...