Lung cancer mortality in the Mayo Lung Project: Impact of extended follow-up

Background: The Mayo Lung Project (MLP) was a randomized, controlled clinic al trial of lung cancer screening that was conducted in 9211 male smokers b etween 1971 and 1983. The intervention arm was offered chest x-ray and sput um cytology every 4 months for 6 years; the usual-care arm was advised at t rial entry to receive the same tests annually. No lung cancer mortality ben efit was evident at the end of the study. We have extended follow-up throug h 1996, Methods: A National Death Index-PLUS search was used to assign vita l status and date and cause of death for 6523 participants with unknown inf ormation. The median survival for lung cancer patients diagnosed before Jul y 1, 1983, was calculated by use of Kaplan-Meier estimates. Survival curves were compared with the log-rank test. Results: The median followup time wa s 20.5 years. Lung cancer mortality was 4.4 (95% confidence interval [CI] = 3.9-4.9) deaths per 1000 person-years in the intervention arm and 3.9 (95% CI = 3.5-4.4) in the usual-care arm (two-sided P for difference = .09), Fo r participants diagnosed with lung cancer before July 1, 1983, survival was better in the intervention arm (two-sided P = .0039). The median survival for patients with resected early-stage disease was 16.0 years in the interv ention arm versus 5.0 years in the usual-care arm. Conclusions: Extended fo llow-up of MLP participants did not reveal a lung cancer mortality reductio n for the intervention arm. Similar mortality but better survival for indiv iduals in the intervention arm indicates that some lesions with limited cli nical relevance may have been identified in the intervention arm.