Anuradha Saokar MD, Abstract Co-Author: Nothing to Disclose

Marion K Jantsch MD, Presenter: Nothing to Disclose

Peter Florin Hahn MD, PhD, Abstract Co-Author: Nothing to Disclose

Peter Raff Mueller MD, Abstract Co-Author: Nothing to Disclose

Mukesh Gobind Harisinghani MD, Abstract Co-Author: Nothing to Disclose

Lymph nodes measuring ≥ 10 mm on MRI are considered pathologically enlarged while smaller nodes are considered benign. Adopting this cut-off value often leads to undercalling metastases in subcentimeter sized nodes. The purpose of our study was to determine the optimal size threshold at MR imaging that would allow accurate diagnosis of nodal metastastic disease.

Sixty-five patients with genitourinary cancer (prostate (38), bladder (16), renal (4), penile (5), testicular cancer (2)) had 331 pathologically proven lymph nodes in the pelvis and retroperitoneum: benign = 179 and malignant = 152. The MR images were retrospectively reviewed and the short-axis diameter of the nodes was recorded. Sensitivity, specificity and predictive values were calculated using different size cut off values. Receiver operating characteristic curve (ROC) was drawn to determine the accuracy for optimal size threshold.

Of the 331 pathologically proven lymph nodes, 179 were benign and 152 were malignant. Using the conventional ≥ 10 mm size threshold, the sensitivity, specificity, negative (NNP) and positive predictive values (PPV) were 37.7 %, 96.7 %, 90.5 % and 64.9 % respectively. For other size thresholds the values were as follows; ≥ 7 mm: sensitivity 60. 3%, specificity 83.9%, PPV 90.5%, NPV 64.9%; ≥ 5mm: sensitivity 80.8; specificity 57.2 %; PPV 61.3 %; NPV 78.0 %; ≥ 15 mm: sensitivity 15.9 %; specificity 99.4 %; PPV 96 %; NPV 58.5 %. The area under the ROC curve for ≥ 7 mm was 0.791.

The optimal size threshold for characterizing abdominal or pelvic lymph nodes on MRI appears to be 7 mm. Size thresholds lower than 7 mm allow better sensitivity but at cost of specificity, and conversely thresholds above 7 mm allow better specificity but at cost of sensitivity.

Saokar, A, Jantsch, M, Hahn, P, Mueller, P, Harisinghani, M, Nodal Metastatic Disease: What Is the Optimal Size Threshold on MR for Detecting Metastatic Nodes.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4417227.html