Lung Cancer.pdf

30 F.V. Fossella
Computed Tomography of the Chest
CT of the chest is much more precise than chest radiography in detecting
enlarged hilar and mediastinal lymph nodes, pleural and pericardial effusion,
invasion into the chest wall and mediastinal structures, lymphangitic
carcinomatosis, and smaller lung parenchymal metastases. All of these
findings would have an important bearing on subsequent diagnostic or
therapeutic measures and also on the patient’s prognosis.
When chest CT is used to evaluate mediastinal node metastases, one
must recognize the limitations of this imaging modality. Generally, mediastinal
lymph nodes larger than 1 cm are considered abnormal. However,
the incidence of false-positive findings on chest CT (i.e., detection of an enlarged
node that is not malignant) is about 30%. One reason for this relatively
high incidence of false-positives is the frequent occurrence of benign
causes of mediastinal lymphadenopathy in the lung cancer patient.
These include, for example, reactive hyperplasia from postobstructive
pneumonia, granulomatous inflammation, and anthracosis. The rate of
false-negative findings on chest CT (i.e., failure of CT to show any enlargement
of mediastinal nodes followed by subsequent documentation
of nodal metastasis at mediastinoscopy or thoracotomy) is about 10%.
Computed Tomography of the Abdomen
A dedicated CT scan of the abdomen is generally not required in the routine
evaluation of lung cancer patients because the chest CT typically includes
enough of the upper abdomen to permit evaluation for metastasis
to the liver and adrenals. However, if the clinician’s index of suspicion of
liver metastasis is high (e.g., if the chest CT suggests hepatic involvement
or if the patient has unexplained elevation of the results of liver
function tests), then a dedicated CT scan of the abdomen with a contrast
agent is warranted to conclusively rule out liver metastases if this finding
would affect the patient’s treatment (e.g., if the patient otherwise has
potentially operable NSCLC or if the patient otherwise has limited-stage
SCLC).
Because the incidence of benign adrenal adenoma in the general population
is significant, ranging from 2% to 10%, patients in whom adrenal enlargement
of uncertain etiology noted on a CT scan of the chest or abdomen
is the sole indication of possible metastasis should have further
evaluation to exclude a benign tumor. CT-guided adrenal biopsy would
provide a conclusive diagnosis in this setting. Magnetic resonance (MR)
imaging of the abdomen has also proven useful in this setting, offering a
sensitivity of 96% and a specificity of 100%.
Additional Radiographic Studies
In the “routine” staging of lung cancer, additional radiographic studies,
including CT and MR imaging of the brain and bone scans, should be