Screening, diagnosis, and staging of lung cancer.

Lung cancer has now displaced coronary heart disease as the single leading cause of excess mortality among smokers in the United States. Because screening by chest radiography and sputum cytology did not result in a reduction in lung cancer mortality, current research is directed at identifying earlier markers of malignancy. Molecular genetic and immunohistochemical techniques may now be applied to sputum cytology, and it may be possible to use such tests to screen certain subpopulations who are at extremely high risk for the development of lung cancer. Computed tomography scanning remains the most sensitive imaging technique for the evaluation and staging of patients with both small cell and non-small cell lung cancer. Several prospective trials have now shown that the specificity and sensitivity of computed tomography in the assessment of mediastinal nodes are still too low to eliminate the need for mediastinoscopy. Patients should not be denied thoracotomy on the basis of enlarged lymph nodes detected by computed tomography scan alone, and histologic verification of tumor involvement is essential, especially for patients who have obstructive pneumonitis. For extrathoracic staging, the diagnostic sensitivity and specificity of computed tomography and ultrasound are similar for the detection of liver metastases, but computed tomography is a more sensitive tool for detecting extrahepatic abdominal metastases. Monoclonal antibody imaging techniques currently do not seem to be either sensitive or specific enough to replace any of the current staging procedures more commonly in use.