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Abstract
Rationale: Prior studies have questioned whether prevailing eligibility criteria for
lung cancer screening are sufficiently inclusive of former smokers who remain at elevated
risk of disease outside current screening windows.Objectives: To characterize the
percentage of the reducible relative risk (RR) remaining for lung cancer as a function
of years since quitting (YSQ).Methods: MEDLINE and PubMed were searched from January
2011 to May 2018; key search terms included "smoking" and "cancer." Current smoker
RRs were extracted to represent former smokers at 0 YSQ; data were transformed assuming
a lognormal distribution.Results: The main review included 49 prospective cohorts
across 18 studies comprising a total of 139 RRs from 20 countries and territories.
At 1 year since quitting, the percentage of reducible RR remaining for lung cancer
was 81.4% (64.1-98.2%). At 5 YSQ, the percentage of reducible RR remaining was 57.2%
(45.7-67.3%); at 10 years, it was 36.9% (28.3-47.9%); at 15 years, it was 26.7% (20.2-34.3%);
and at 20 years, it was 19.7% (13.3-26.4%). If eligibility criteria in the United
States were broadened to screen former smokers at up to 20 YSQ, we estimate an additional
4.2 (3.9-4.5) million former smokers between 55 and 80 years of age would be eligible
for lung cancer screening.Conclusions: At the critical screening threshold of 15 YSQ,
the percentage of excess risk for lung cancer remains high and only marginally declines
at time points afterward, excluding millions of former smokers who remain at elevated
risk of malignancy. A risk-based algorithm for lung cancer screening that deemphasizes
time after cessation as a key screening determinant would more likely capture these
former smokers who remain at elevated risk of malignancy.