What we could know from the semiannually repeated screening with low-dose helical CT in a high-risk cohort over 10 years: Update of Anti-Lung Cancer Association project

Abstract

7568 Background: There have been several randomized trials of low-dose helical CT (LDCT) screening for lung cancer. However, all trials are in progress. Therefore, before they are completed, we summarized what we could know from an update of Anti-Lung Cancer Association project, which was regarded as a longer-term study with LDCT performed at shorter intervals and with a larger number of detected cancers than any other single-armed studies. Methods: Among 2,120 participants, 1,877 (mean age 64 years, 88% male, and 84% smoker) underwent semiannually repeated screening from 1993 to 2004 (median, 3.5 years). We investigated (1) survival of patients with screening detected lung cancers, (2) presence of a stage shift (indicator of a mortality benefit), (3) appropriate duration of repeated screening, (4) identification of high-risk group by age, sex, and smoking, and (5) appropriate screening intervals by high-risk group (6 months or 1 year). Results: (1) The 5- and 10-year survival rates were 84.5% and 84.5%, respectively, in repeated screening group (n = 57) and were 68.7% and 38.1%, respectively, in initial screening group (n = 19) (P = 0.208). (2) Only in invasive adenocarcinoma, both proportion of stage II to IV and tumor size were negatively correlated with duration of repeated screening (r = −0.77, P = 0.007 and r = − 0.60, P = 0.029, respectively). (3) Detection rate of all incidence cancers were positively correlated with duration of repeated screening (r = 0.50, P = 0.020). However, detection rate remained unchanged until 5 years of repeated screening. Moreover, stage shift did not occur until 5 years of repeated screening. (4) Female sex (HR 2.9, P = 0.015) and smoking (HR 2.7, P = 0.046) were demographic risk factors for lung cancer detection at repeated screening. The accumulated 10-year detection rates for female smokers (n = 91), male smokers (n = 1,557), and non-smokers (n = 229) were 15.1%, 6.2%, and 4.3%, respectively (P = 0.002). (5) The estimated relative cancer detection powers of annual screening to semiannual screening were 50% and 57% for female and male smokers with lung cancer, respectively. Conclusions: Semiannually repeated LDCT screening over 5 years might be beneficial to smokers, especially female smokers. No significant financial relationships to disclose.