Mural and extramural venous invasion and prognosis in colorectal cancer.

Background: Extramural venous invasion is a known independent predictor of poor prognosis after resection of colorectal adenocarcinoma, but the prognostic value of mural venous invasion alone and the association between venous invasion and prognosis within tumor stages has received little research attention.
Objective: This study aimed to determine whether associations between mural and extramural venous invasion and outcome differ among tumor stages after adjustment for other factors known to influence prognosis.
Design: This study is a retrospective analysis of prospectively collected data.
Settings: Data were drawn from a registry of 3040 consecutive patients undergoing resection between 1980 and 2005 under the care of specialist surgeons in a tertiary referral public hospital and an affiliated private hospital. A standardized protocol was used for the pathological assessment of specimens.
Main Outcome Measures: The primary outcomes measured were overall survival, cancer-specific survival, and recurrence.
Results: There was no significant association between venous invasion and survival in stages A (n = 544) or B (n = 1078). In stage C (n = 899), overall survival time was significantly shorter in patients with mural invasion alone or extramural invasion (both p < 0.001) than in those without invasion, and this persisted after adjustment for other prognostic variables. Equivalent bivariate associations were found in stage D, but only the effect of extramural invasion persisted after adjustment.
Limitations: Our findings arise from the experience of a single surgical group and may not be generalizable to other settings. Only hematoxylin and eosin staining was used.
Conclusions: The association between venous invasion and prognosis was stage specific. Both mural venous invasion alone and extramural venous invasion independently predicted overall survival in patients with stage C tumors, but not in patients with stages A, B, or D tumors. Although mural invasion alone was rare, the separate reporting of both mural and extramural invasion in patients with stage C tumor is informative and desirable.