The significance of extramural venous invasion in R1 positive rectal cancer

Evidence has shown that a positive resection margin (R1) is a key determinant of subsequent local recurrence and a poor prognostic factor in rectal cancer. The aim of this study was to evaluate the outcomes and prognosticators in patients with R1 resection of rectal cancer.

Retrospective study of all patients operatively managed within our institution between April 2008 and April 2013 for rectal cancer. Baseline demographics and multiple outcome measures recorded. Overall survival (OS), disease-free survival (DFS) and recurrence were the primary outcome measures.

Overall, there were 306 primary rectal cancers. Seventy-six percent were grade T3/4 tumours. OS was 30 months. R1 rate was 16 % (48 patients). Thirty-one patients underwent APR and 17 AR. In patients who responded to neoadjuvant chemotherapy (NAC), overall survival was 55 months, with no extramural venous invasion (EMV) seen in this cohort. In non-responders OS was 29 months, with EMV in 48 %. In patients who did not receive NAC, OS was 23 months, with EMV in 74 %. EMV is a strong predictor for poor survival following R1 (p = 0.001). We also found a correlation between number of positive nodes and OS/DFS (p = 0.004).

In this small cohort of patients with R1 positive rectal cancers, response to NAC is the strongest predictor of poor overall and disease-free survival. In patients who respond to NAC, OS and DFS has been shown to be positive, with a reduced rate of EMV.