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The Philadelphia Pulmonary Neoplasm Research Project.

The Philadelphia Pulmonary Neoplasm Research Project (PNRP) was the pioneer prospective screening program for early detection of lung cancer and has been widely publicized.1The PNRP study population was composed of more than 6,000 men aged 45 years or more. Recruitment of subjects began Dec 4, 1951, and ended four years later.2 Screening was attempted by two techniques. Each subject had a 70-mm chest photofluorograph taken and completed a questionnaire about smoking habits, occupation, and respiratory symptoms. Anyone with obvious lung cancer on initial screening was excluded.2During the ensuing decade, a concerted effort was made to rescreen all subjects semiannually, in the hope that enough "curable" cases of lung cancer would be found to justify continuation or amplification of the program. Unfortunately, there were problems associated with the overall design of the PNRP. Twenty years ago, evidence linking cigarette smoking to lung cancer was not as