My name is Elizabeth Lee. I'm a fellow in the Department of Radiology at the University of Michigan. And we'll be discussing the role of CT in imaging of esophageal cancer. Objectives for this presentation include developing an understanding for the role, as well as limitations of CT in staging of esophageal cancer. We will first start with a pre-lecture assessment question. CT for staging of esophageal cancer allows for optimal assessment of A, the degree of esophageal wall involvement, B, local paraesophageal lymph node metastatic disease, C, sites of distant metastatic disease, or D, all of the above. Contrast enhanced CT of the chest and abdomen can help identify sites of metastatic disease and whether there is possible invasion of the tumor into adjacent structures, such as the trachea. Optimal imaging technique is performed with both oral and intravenous contrast when possible, given patient factors such as GFR in order to increase the conspicuity of the primary tumor and metastatic disease if present. The TNM classification of esophageal cancer uses depth of tumor invasion into the esophageal wall, lymph node involvement, and the presence of metastatic disease to stage patients and determine treatment plans. CT can provide information regarding each of these. The T stage is divided by the layers of the esophageal wall, with higher T stages indicating deeper invasion. CT, however, is not able to differentiate between T1, T2, and T3 disease accurately. This EUS image shows an isoechoic mass, denoted by the blue calibers invading into the muscularis propria, that is T2 disease. On the corresponding CT image, the tumor is not discernible, let alone the degree of wall invasion. Although CT is not able to determine T1 to T3 disease, it may allow for exclusion of T4 disease if there is preservation of the fat planes between the tumor and adjacent structures, as shown on this CT image. CT may be able to suggest T4 disease if findings, such as loss of intervening fat planes, displacement of mediastinal structures, greater than 90 degree contact of the tumor with aorta, or pericardial thickening or fusions are present. However, the reported sensitivities and specificities of these findings in the literature varies. Therefore, even if intervening fat planes are lost on CT, T4 disease may not be present, if the patient is taken to the operating room. Here is an example of T4 disease. On this contrast enhanced CT, there's extensive soft tissue abnormality in the mediastinum due to esophageal cancer. The tumor abuts the posterior trachea, indenting its wall, and there's loss of the normal intervening fat planes. In addition, there is loss of the fat plane between the esophagus and the aorta. Abnormal foci of gas are seen anterior to the descending thoracic aorta, as well as extravasation of intravenous contrast into the esophagus due to an aorto-esophageal fistula. Here is another example of T4 disease. On this contrast enhanced CT, there's esophageal wall thickening and abnormal soft tissue attenuation within the superior mediastinum. An acrotic central component of the mass is noted near the great vessels. The tracheal diameter is diminished, with irregularity of the wall due to tracheal invasion of esophageal cancer with fistula formation. CT can be used to assess for regional lymph node involvement or N stage. The sensitivity of CT, however, is poor, ranging between 42 and 50%. And this is due to the fact that normal sized lymph nodes may have metastatic disease. Specificity of lymph node enlargement is better with reported ranges of 83 to 93%. An example of regional lymph node involvement, this gastro-hepatic lymph node, measuring greater than one centimeters, is concerning for regional lymph node involvement in this patient with a distal esophageal cancer. M stage divides those with and those without distant metastatic disease and is a strength of CT in the imaging of esophageal cancer. The most common sites of metastatic disease from esophageal cancer include the liver, lungs, bone, and adrenal glands. Here is an example of a metastatic lesion to the liver from esophageal cancer. An ill defined hypo-enhancing mass is present within the anterior portion of the right lobe of the liver. Another example of metastatic disease from esophageal cancer, numerous lobulated pulmonary nodules are present in the lower lobes. There are additional limits of CT. First, in patients with symptoms suggestive of esophageal cancer, CT should not be used for initial assessment, given its limited sensitivity. Secondly as discussed before, CT cannot distinguish T1 to T3 disease, given its poor spatial resolution when compared to EUS. Finally EUS is more sensitive than CT when assessing regional lymph nodes for the presence of metastatic disease. An example of the inability of CT to identify primary tumors, on this contrast enhanced CT of the esophagus, the wall thickness is normal, and the normal fat planes are present. The PET scan, however, should clearly demark a hypermetabolic focus in the distal esophagus, representing the patient's primary tumor. Now for our post-lecture question, CT for the staging of esophageal cancer allows for optimal assessment of A, the degree of esophageal wall involvement, B, local paraesophageal lymph node metastatic disease, C, sites of distant metastatic disease, or D, all of the above. The best answer is C, sites of metastatic disease. Esophageal wall invasion is better assessed with EUS, as CT has limited ability to determine the degree of esophageal wall involvement, that is, T1 to T3 disease. Local paraesophageal lymph node involvement is also more sensitive when assessed with EUS compared to CT. These are our take home points. CT of the chest and abdomen, for the staging of esophageal cancer, allows for identification of sites of distant metastatic disease, may help identify gross mediastinal invasion, and is specific for regional lymph node disease when lymph nodes are enlarged. The findings on CT can help guide clinicians in initial staging and appropriate therapeutic options. Thank you for your attention. I hope you enjoy the remainder of the course.
