Lung Cancer.pdf

Thoracic Imaging Techniques 43
95% to 100% (Li et al, 1996; Klein and Zarka, 1997; Westcott et al, 1997).
Specific benign diagnoses are more difficult but have been made in up to
91% of patients with a benign lesion undergoing TTNA biopsy (Klein et al,
1996). Complications, most notably pneumothorax and hemorrhage,
occur in approximately 5% to 30% of patients. Hemorrhage is almost always
self-limiting, and only about 15% of patients with pneumothoraces
eventually require chest tube placement (Klein and Zarka, 1997).
TTNA biopsy of enlarged hilar and mediastinal nodes is useful in determining
the stage of lung cancer. CT-guided TTNA biopsy has been
proven to be more cost-effective and less invasive than mediastinoscopy
and can be used to sample nodes that are inaccessible at mediastinoscopy
(e.g., nodes in the aortopulmonary window or in the subcarinal/azygoesophageal
region).
Staging of Lung Cancer
Non–Small Cell Lung Cancer
In patients with non–small cell lung cancer (NSCLC), treatment and prognosis
are usually determined on the basis of the disease stage. Patients
with NSCLC are staged according to the International System for Staging
Lung Cancer (Mountain, 1997). This system describes the extent of
NSCLC in terms of the primary tumor (T descriptor), lymph nodes (N descriptor),
and metastases (M descriptor). The TNM descriptors can be determined
clinically with a history, a physical examination, and radiologic
imaging or by pathologic analysis of samples obtained with biopsy or
surgery.
Primary Tumor
The T descriptor defines the size, location, and extent of the primary
tumor. Because the extent of the primary tumor determines whether the
disease will be treated with surgical resection or palliative radiation therapy
or chemotherapy, imaging is used to assess the degree of pleural,
chest wall, and mediastinal invasion. CT and magnetic resonance (MR)
imaging are useful in confirming gross chest wall or mediastinal invasion
but are inaccurate in differentiating between anatomic contiguity and subtle
invasion. MR imaging has superior soft-tissue contrast resolution and
multiplanar ability and is thus particularly useful in the evaluation of superior
sulcus tumors—i.e., assessment of invasion of the brachial plexus,
subclavian vessels, and vertebral bodies (Figure 3–2).
Up to 33% of patients with NSCLC have a malignant pleural effusion or
pleural metastases at presentation. Such tumors are classified as T4 lesions
and are not resectable. The diagnosis of pleural metastases or malignant
pleural effusion can be difficult: CT often fails to show pleural thickening