Screening for lung cancer in high-risk groups: current status of low-dose spiral CT scanning and sputum markers

Lung cancer is the number one cause of death from cancer in the United States. Currently, there is no official recommendation to screen for lung cancer even in high-risk populations. Accordingly, we wait for patients to present with symptoms. Only 15-20% of patients are stage I lung cancer at diagnosis. Past screening trials with chest roentgenogram and sputum cytology did not show a reduction of lung cancer mortality in the screened population. Since the completion of those trials in the early 1980s we have learned that the chest X ray is not sensitive at detecting lesions <2 cm in size, and patients with chronic obstructive pulmonary disease (COPD) have a 4- to 6-fold increased risk of lung cancer independent of their smoking history. Recent trials with spiral computed tomography (CT) scan screening have detected 80-85% of lung cancers while they are stage I. The problems related to spiral CT screening are the cost and the frequent detection of benign lesions. Algorithms are being developed to try and prevent unnecessary biopsies and/or surgery. Sputum cytology is currently the only clinically approved sputum test for detecting lung cancer. However, in patients with moderate dysplasia of cytology, the LIFE autofluorescence bronchoscopy system may yield an increased sensitivity of detecting precancerous or cancerous lesions. More studies are needed before the LIFE system can be adopted as a standard clinical tool. Currently, investigators are evaluating the sputum for early lung cancer detection markers. The marker that is the most developed is the monoclonal antibody to the heterogeneous nuclear ribonucleoprotein A2/B1 on the sputum epithelial cell surface. Encouraging preliminary results have been reported and trials are ongoing. The future looks bright for the field of lung cancer screening.