Squamous cell cancer of hypopharynx and larynx – Evaluation of metastatic nodal disease based on computed tomography perfusion studies

Abstract

In patients with squamous cell cancer metastatic disease in lymph nodes still remains the single most important negative predicting factor and when detected, it reduces overall 5-year survival by 50%. The aim of the study was to evaluate contrast-enhanced computed tomography (CECT) with computed tomography perfusion (CTP) examination in order to differentiate malignant from non-malignant cervical lymph nodes in patients with squamous cell cancer of hypopharynx and larynx. This was a prospective three-center study. From November 2007 until March 2010 33 consecutive patients with squamous cell cancer of the hypopharynx and 27 patients with laryngeal cancer underwent computed tomography (CT) examination followed by CTP. During first part of examination 80 ml of contrast was administered, with flow rate 1 ml/s and 100 s delay; standard head and neck examination was performed. Next, perfusion images were acquired with the coverage of 8 cm and different groups of lymph nodes were evaluated - groups II, III, IV and V. Perfusion maps for basic parameters (blood flow [BF], blood volume [BV], mean transit time [MTT] and permeability surface [PS]) were reconstructed for all patients using dedicated software. The long and short axis diameters, the density of the node before and after contrast medium administration and average values of each perfusion parameter were calculated for every node separately. Results were compared with histologic analysis of resected nodes. Out of the total number of 293 nodes evaluated on CECT and CTP it was possible to correlate 208 resected nodes with histologic findings. 125 of them were proven to be malignant and 83 were benign. Malignant nodes showed remarkably higher density and hyperperfusion, comparing to benign ones. The average density values in Hounsfield units (HU) for cervical nodes were: 91.9HU for metastatic comparing to 72.3 HU for non-metastatic, but this difference did not show statistical significance. The average value of BF in malignant nodes was 136.4 ml/100g/min, BV was 7.7 ml/100g, MTT was 4.4s and PS was 19.4 ml/100g/min. The average values for benign nodes were: BF was 80.7 ml/100g/min, BV was 4.7 ml/100g, MTT was 5.6s and PS was 12.8 ml/100g/min. Comparing to non-malignant nodes, malignant ones showed significantly higher BF, BV and PS values (p<0.05). Although CECT findings may draw our attention, pointing at abnormal morphology of the node, CTP seems to provide additional functional information regarding its possible malignancy. CTP may be useful in differentiation between malignant and benign lymph nodes, based on evaluation of the value of BF, BV and PS.