MRI of Extramural Venous Invasion in Locally Advanced Rectal Cancer: Relationship to Tumor Recurrence and Overall Survival.

Purpose To study the relationship between MRI-defined extramural venous invasion (EMVI) prior to treatment and prognosis in patients with locally advanced rectal cancer treated with neoadjuvant chemotherapy-radiation therapy followed by surgery. Materials and Methods This retrospective study included 517 patients with locally advanced rectal cancer evaluated from August 2008 to December 2014. Baseline and posttherapy MRI and follow-up data were retrieved for all patients. After training by using 328 cases with pathologic evaluation of EMVI after therapy, radiologists evaluated baseline MRI for EMVI status in addition to tumor size and characteristics, nodal status, and invasion of the mesorectal fascia. Reader reproducibility was determined by using κ coefficient. Kaplan-Meier curves and adjusted Cox models were used to determine the relationship of baseline MRI parameters to overall survival, metastasis-free survival, and local relapse-free survival. Results Among 517 patients, 335 (64.8%) were men; the mean age was 55.6 years ± 11.5 (standard deviation). At baseline, radiologists identified 259 of 517 (50%) patients with EMVI by using MRI. In adjusted analysis, EMVI and mesorectal fascial invasion at baseline MRI were predictors of metastasis-free survival (hazard ratio, 0.3 and 0.6; P ˂ .01 and P ˂ .02, respectively) and overall survival (hazard ratio, 0.5 and 0.5; P = .01 and P = .02, respectively). EMVI was the only factor associated with local relapse-free survival (hazard ratio, 0.3; P ˂ .01). The κ coefficient for determination of EMVI was 0.80. Conclusion Extramural venous invasion (EMVI) can be reliably evaluated with MRI. The presence of EMVI was associated with greater risk of local and distant tumor recurrence and overall death in patients with locally advanced rectal cancer treated with neoadjuvant chemotherapy-radiation therapy. © RSNA, 2018 Online supplemental material is available for this article.