Heesakkers RA et al. (2008) MRI with a lymph-node-specific contrast agent as an alternative to CT scan and lymph-node dissection in patients with prostate cancer: a prospective multicohort study. Lancet Oncol 9: 850–856

Diagnostic pelvic lymph-node dissection (PLND) is the gold standard for detection of nodal metastases in patients with prostate cancer. Introduction of the lymph-node-specific intravenous contrast agent, ferumoxtran-10, has increased the potential accuracy of CT and MRI for detecting metastases. Heesakkers and colleagues carried out a prospective, multicohort study to compare the diagnostic accuracy of multidetector CT (MDCT) with that of magnetic resonance lymphangiography (MRL), and to investigate whether a negative MRL result can preclude the need for PLND.

A total of 375 patients with prostate cancer who had an intermediate or high risk of lymph-node metastases were enrolled in the study. In relation to the detection of lymph-node metastases, the sensitivity of MDCT and MRL were 34% and 82%, respectively. Specificity was 97% for MDCT compared with 93% for MRL. The negative predictive values for MDCT and MRL were 88% and 96%, respectively, and positive predictive values were 66% and 69%, respectively. A total of 61 patients had lymph-node metastases, and in 50 patients these metastases were detected by MRL. In at least 30% of patients with lymph-node metastases, positive nodes were detected only by MRL, as they were outside the routine PLND area.

The authors conclude that MRL has higher sensitivity than MDCT to detect potential lymph-node metastases in patients with prostate cancer. In patients with negative MRL findings, the probability of lymph-node metastases is low enough to preclude PLND.