USPIO – enhanced rectal cancer specimen MRI: how well does it correlate with node identification at histopathology?

Abstract

Introduction: Detection of lymph node (LN) metastasis is important for the optimal management of rectal cancer patients. Ultrasmall‐particle superparamagnetic iron oxide (USPIO) contrast enhanced magnetic resonance imaging (MRI) has emerged as an effective method of assessing nodal involvement in various malignancies. We have investigated the correlation between nodes seen on specimen MRI and those found at histopathology and the optimum time interval between contrast injection and surgery in USPIO mesorectal lymphography.Method: Thirteen rectal cancer patients underwent MRI before and 24 h after intravenous infusion of USPIO contrast (Sinerem®, Advanced Magnetics Inc, Cambridge, MA, USA). Total Mesorectal Excision (TME) surgery was followed by fixed specimen MRI. Lymph nodes seen on specimen MRI and those found at pathology were compared for studies performed <5 days and ≥5 days prior to surgery.Results: Histopathological LNs found correlated well with those seen on specimen MRI (all patients, r = 0.73; P = 0.005, figure). Correlation was better for the <5 day group (r = 0.84; P = 0.01) than for the ≥5 day group (r = 0.54; P = 0.35). Discussion: USPIO specimen MRI is useful in mesorectal LN assessment. We demonstrate good correlation between specimen MRI and histopathology and show that fewer errors occur in assessment when the time interval between contrast injection and surgery is <5 days.