Supreeta Arya MD, Presenter: Nothing to Disclose

Sonal Mahalwar MBBS, Abstract Co-Author: Nothing to Disclose

Nilesh Sable, Abstract Co-Author: Nothing to Disclose

To determine the incremental value of diffusion-weighted MR imaging over conventional MRI in the detection of metastatic lymph nodes in oral tongue squamous cell carcinoma (SCC).  

A prospective study was undertaken in 30 patients of stage T2 – T4 oral tongue SCC at a tertiary referral oncology centre. Cases receiving neoadjuvant therapy were excluded. All cases underwent MRI on a 1.5T magnet. Multiplanar spin echo sequences (T1W, T2W, STIR and postgadolinium T1W) were obtained for conventional MRI. DWIMRI was performed using b0 and b1000 values. ADC maps were used for calculating ADC values for nodes at each nodal station (IA, IB, II-V). All cases underwent elective neck dissection, either unilateral (n= 16) or bilateral (n=14). In all 44 necks were operated; modified radical neck dissection (MRND) in unilateral dissections and MRND/supra-omohyoid neck dissection on the contralateral side. The imaging findings were correlated with histopathology , both on a per neck basis and per nodal station level basis. Institutional review board clearance was obtained before recruiting patients for the study.

Conventional MR imaging using all criteria revealed a sensitivity of 66.6%, specificity of 90%, PPV of 88.8 %, NPV 69.2 %, and accuracy of 77.2% , on a per neck basis. On a per nodal station basis , a sensitivity of 63.8%, specificity of 90.9%, positive predictive value (PPV) of 69.6% , negative predictive value( NPV) of 88.5% and accuracy of 84.2% were obtained. There was significant overlap in the range of ADC values of benign and metastatic nodes. The cut off ADC value obtained from the ROC curve was 0.95x10-3mm2. Using this ADC value the incremental value of DWMRI over conventional MRI  yielded a sensitivity of 77.5%, specificity of 77.2 %, positive predictive value of 50.8%, negative predictive value of 92 % and accuracy of 77.3%.

DWI MRI added to conventional MRI increased sensitivity and NPV , but due to overlap in ADC values of metastatic and reactive nodes, the PPV reduced significantly. DWI of lymph nodes may not be as accurate as initially reported in literature.   

The debate between elective neck dissection and watchful waiting for the clinically negative neck is not yet settled. DWI MRI cannot improve surgical staging; but if watchful waiting is the decided policy,  adding DWI-MRI to conventional MRI could contribute by an increase in NPV.

Arya, S, Mahalwar, S, Sable, N, The Incremental Value of Diffusion Weighted Imaging over Conventional MRI for Detection of Metastatic Nodes in Squamous Carcinoma of the Oral Tongue: Do We See the Glass Half Full or Half Empty? .  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14017798.html