Chest CT for Known or Suspected Lung Cancer

Chest radiograph fiberoptic bronchoscopy high-resolution CT magnetic resonance imaging node solitary pulmonary nodule tumor transbronchial needle aspiration transthoracic needle aspiration Lung cancer causes more cancer-related deaths in the United States than any other malignancy. Two facts account for this disturbing observation. The incidence of lung cancer in both men and women has progressively increased in recent years. Treatment of lung cancer remains largely ineffective. The overall 5-year survival rate for patients with lung cancer may be as low as 7 percent to 14 percent. The best survival rates are found in the subgroup of patients with lung cancer with surgically resectable tumors. Clinicians, therefore, are vitally interested in recognizing lung cancer early and determining surgical resectability accurately. Computed tomography (CT) was introduced into clinical practice in the 1970s as an exciting new method for imaging the thorax. Since then, clinicians have come to rely heavily on CT for evaluating potentially malignant chest lesions and the intrathoracic spread of lung cancer. A survey of thoracic surgeons in 1986 revealed that more than one third of these surgeons order CT routinely for all patients with lung cancer and 62 percent more selectively obtain CT scans.1Epstein DM Stephenson LW Gefter WB Van der Voorde F Aronchick JM Miller WT Value of CT in the preoperative assessment of lung cancer..Radiology. 1986; 161: 423-427Crossref PubMed Scopus (35) Google Scholar Despite the frequency at which clinicians obtain CT scans, it is still unclear what role CT plays in the treatment of patients with suspected and known lung cancers. Clinicians are especially concerned with how well CT performs in distinguishing benign from malignant solitary pulmonary nodules (SPN) and in staging the primary tumor (T) and regional node (N) extent of lung cancer (Table 1). In this review, the role CT should play in evaluating SPNs and assessing the T and N stages of lung cancer will be critically evaluated.Table 1The Role of CT for Primary Tumor (T) and Node Involvement (N) Staging in Non-Small-Cell Lung CancerStage and NodeCT Role EvaluatedPrimary tumor stage Tx or Tis Tumor not radiographically detectedNo! by definition T1 A tumor ≤3 cm in greatest dimension without local or proximal bronchus invasionYes for invasion and also to distinguish benign from malignant nodules T2 A tumor >3 cm in greatest dimension or with visceral pleura invasion or associated atelectasis/obstructive pneumonitisYes for invasion and bronchial spread T3 A tumor invading chest wall, diaphragm, or mediastinal pleura or pericardiumYes for invasion T4 A tumor involving heart, great vessels, trachea, esophagus, vertebral bodies, or carura; or with malignant effusionYes for invasion but no for malignant effusionNode involvement by tumor N0 No regional nodes involvedYes N1 Ipsilateral hilar nodes onlyNot emphasized N2 Ipsilateral mediastinal and/or subcarinal nodesYes N3 Contralateral mediastinal, hilar, scalene, and/or supraclavicular nodes; ipsilateral, scalene, and/or supraclavicular nodesYes Open table in a new tab An appealing way to distinguish between benign and malignant SPNs would be to rely on some combination of radiographic features seen on either the standard frontal and lateral chest radiograph (CXR) or linear tomography. Although there are no classic radiographic features of lung cancer, size is an obvious consideration. Nodules smaller than 8 mm are usually considered benign, and nodules larger than 3 cm are more often malignant. There are other radiographic features strongly suggesting the benign nature of an SPN. The most reliable of these radiographic features seem to be documented absence of growth of the SPN over a 2-year period and substantial calcification in either a central, diffuse, laminated, or popcorn pattern. Other variables considered include nodule shape, edge definition, satellite lesions, and cavitation. Unfortunately, evaluation of these radiographic features on standard roentgenograms may often be subjective. In 1980, Siegelman et al2Siegelman SS Zerhouni EA Leo FP Khouri NF Stitik FP CT of the solitary pulmonary nodule..AJR. 1980; 135: 1-13Crossref PubMed Scopus (225) Google Scholar suggested that CT could be used to distinguish between benign and malignant nodules in a quantitative fashion. Because CT is more sensitive than standard radiographic techniques in detecting calcification and the extent of calcification found on CT can be expressed quantitatively as a density, Siegelman's group postulated that an SPN with density numbers suggesting extensive calcification would be most probably benign. 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