Future diagnostic procedures.

Although the exact proportion of patients with carcinoma in situ in whom disease will progress to invasive lung cancer is not known, and although there have been reports that some individuals may continue to show malignant cells in sputum for several years without symptoms or abnormality on chest radiograph, untreated or suboptimally treated carcinoma in situ has been shown to progress to invasive cancer or metastatic disease. A study by Frost and co-workers showed that cancer developed in approximately 10% of individuals with moderate atypia and 40% of those with severe atypia in sputum cytology. Therefore, the proportion of individuals with carcinoma in situ in whom invasive cancer will develop is likely to be greater than 40%. Lung cancer is almost uniformly fatal when untreated, and, if the disease is allowed to progress to the invasive stage, the results of currently available therapy are poor. A lesson must be learned from cervical cancer screening. As has been shown by Anderson and co-workers, if individuals harboring dysplasia or carcinoma in situ are actively sought for and treated by laser or cryotherapy, the incidence and mortality of invasive cervical cancer can be reduced to extremely low levels. If current work directed toward detecting early lung cancer in sputum cytology specimens in high-risk groups using quantitative image cytometry or molecular markers is successful, the ability to localize small preinvasive lesions with fluorescence bronchoscopy will become even more important for the pulmonologist or thoracic surgeon. Endoscopic ultrasound can be used to determine the depth of tumor infiltration into the bronchial wall or adjacent structures. Biopsy of mediastinal and peribronchial lymph nodes can be performed under sonographic guidance for more accurate staging. By coupling sensitive diagnostic tools to new treatment modalities, such as chemoprevention and various endobronchial therapies, it is hoped that the traditionally poor prognosis for patients with lung cancer can be altered in the near future.