• Department of Oncology/Hematology, Marshfield Clinic, Marshfield, WI, USA. Electronic address: hocking.william@marshfieldclinic.org.

Lung cancer is the major cause of cancer mortality. One of the aims of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) was to determine if annual screening chest radiographs reduce lung cancer mortality. We enrolled 154,900 individuals, aged 55-74 years; 77,445 were randomized to the intervention arm and received an annual chest radiograph for 3 or 4 years. Participants with a positive screen underwent diagnostic evaluation under guidance of their primary physician. Methods of diagnosis or exclusion of cancer, interval from screen to diagnosis, and factors predicting diagnostic testing were evaluated. One or more positive screens occurred in 17% of participants. Positive screens resulted in biopsy in 3%, with 54% positive for cancer. Biopsy likelihood was associated with a mass, smoking, age, and family history of lung cancer. Diagnostic testing stopped after a chest radiograph or computed tomography/magnetic resonance imaging in over half. After a second or subsequent positive screen, evaluation stopped after comparison to prior radiographs in over half. Of 308 screen-detected cancers, the diagnosis was established by thoracotomy/thoracoscopy in 47.7%, needle biopsy in 27.6%, bronchoscopy in 20.1% and mediastinoscopy in 2.9%. Eighty-four percent of screen-detected lung cancers were diagnosed within 6 months. Diagnostic evaluations following a positive screen were conducted in a timely fashion. Lung cancer was diagnosed by tissue biopsy or cytology in all cases. Lung cancer was excluded during evaluation of positive screening examinations by clinical or radiographic evaluation in all but 1.4% who required a tissue biopsy.