Extramural venous invasion on pretreatment MRI and surgical pathology: Is there a role in predicting prognosis in rectal cancer?

Abstract

e15165 Background: Extramural venous invasion (EMVI) describes tumor cells invading the veins beyond the muscularis propria and has been previously recognized as a predictor for survival and disease recurrence in rectal cancer. EMVI is generally diagnosed on pathology after surgical resection. Pretreatment MRI has been proposed as a surrogate imaging biomarker for recognition of EMVI. Our objective is to study the prognostic significance of EMVI in rectal cancers based on pretreatment MRI imaging to determine its correlation with overall survival (OS), local recurrence (LR), and distant metastases (DM). We also compare MRI-detected EMVI to EMVI detected on pathology to evaluate correlation. Methods: In this ongoing study, records of rectal cancer patients with a pretreatment staging MRI diagnosed between 2004-2015 were retrospectively reviewed (n = 180). Pretreatment rectal MRIs were evaluated for different imaging characteristics, including EMVI. The endpoint of OS was calculated using the Kaplan-Meier method and compared with a log-rank test. A p< 0.05 was considered significant. Cox proportional hazard ratios for LR and DM were generated using clinical, imaging, and pathologic characteristics. Results: Most patients were male (63%) with a median age at diagnosis of 63 years (28.5-95.2). Eighty percent of patients received neoadjuvant chemoradiation (nCRT) followed by surgery and adjuvant chemotherapy (AC); 20% received nCRT followed by surgery. A pathologic complete response was achieved in 17% of patients. Median survival was 48.5 months (2.6-145.2); five-year OS was 85%. The receipt of AC improved OS (HR 0.40, CI 0.2-0.9). Of 70 patients with EMVI noted on the pretreatment MRI, 22 (31%) had EMVI on pathology (p = 0.05). EMVI on MR was not found to be prognostically significant for OS, LR, or DM. EMVI on pathology was found to be significant for DM (HR 3.74, CI 1.8-8.0). Conclusions: Preliminary results show that pretreatment MR-detected EMVI was not found to be predictive for OS, LR, or DM, but pathologically-detected EMVI was found to be a predictor for DM. Further analysis of the relationship between this surrogate imaging biomarker on post-CRT MRI and outcomes is ongoing.