A population-based cohort study of chest x-ray screening in smokers: lung cancer detection findings and follow-up
1 Center for Thoracic Surgery, University of Insubria, Via Guicciardini, 9, 21100 Varese, Italy
2 Department of Public Health and Community Medicine, University of Verona, Strada Le Grazie 8, 37134 Verona, Italy
3 Epidemiology Observatory, Varese Local Health Authority, Via O. Rossi 9, 21100 Varese, Italy
4 Department of Radiology, Ospedale S. Antonio Abate, Via Pastori 4, 21013 Gallarate, Italy
5 Department of Human Morphology, University of Insubria, Via Monte Generoso 71, 21100 Varese, Italy
6 Respiratory Care Unit, Department of Medicine, Ospedale S. Anna, Via Ravona, 22020 San Fermo della Battaglia, Como, Italy
7 Thoracic Medicine Unit, Department of Medicine, Ospedale S. Antonio Abate, Via Pastori 4, 21013 Gallarate, Italy
BMC Cancer 2012, 12:18 doi:10.1186/1471-2407-12-18Published: 17 January 2012
Case-control studies of mass screening for lung cancer (LC) by chest x-rays (CXR) performed in the 1990s in scarcely defined Japanese target populations indicated significant mortality reductions, but these results are yet to be confirmed in western countries. To ascertain whether CXR screening decreases LC mortality at community level, we studied a clearly defined population-based cohort of smokers invited to screening. We present here the LC detection results and the 10-year survival rates.
The cohort of all smokers of > 10 pack-years resident in 50 communities of Varese, screening-eligible (n = 5,815), in July 1997 was invited to nonrandomized CXR screening. Self-selected participants (21% of cohort) underwent screening in addition to usual care; nonparticipants received usual care. The cohort was followed-up until December 2010. Kaplan-Meier LC-specific survival was estimated in participants, in nonparticipants, in the whole cohort, and in an uninvited, unscreened population (control group).
Over the initial 9.5 years of study, 67 LCs were diagnosed in screening participants (51% were screen-detected) and 178 in nonparticipants. The rates of stage I LC, resectability and 5-year survival were nearly twice as high in participants (32% stage I; 48% resected; 30.5% 5-year survival) as in nonparticipants (17% stage I; 27% resected; 13.5% 5-year survival). There were no bronchioloalveolar carcinomas among screen-detected cancers, and median volume doubling time of incidence screen-detected LCs was 80 days (range, 44-318), suggesting that screening overdiagnosis was minimal. The 10-year LC-specific survival was greater in screening participants than in nonparticipants (log-rank, p = 0.005), and greater in the whole cohort invited to screening than in the control group (log-rank, p = 0.001). This favourable long-term effect was independently related to CXR screening exposure.
In the setting of CXR screening offered to a population-based cohort of smokers, screening participants who were diagnosed with LC had more frequently early-stage resectable disease and significantly enhanced long-term LC survival. These results translated into enhanced 10-year LC survival, independently related to CXR screening exposure, in the entire population-based cohort. Whether increased long-term LC-specific survival in the cohort corresponds to mortality reduction remains to be evaluated.