Final results of the Lung Screening Study, a randomized feasibility study of spiral CT versus chest X-ray screening for lung cancer
Introduction
Lung cancer is the leading cause of cancer-related mortality in both men and women in the United States [1]. Early detection of lung cancer has been explored as a possible method of reducing the lung cancer mortality burden. However, although various approaches to early detection of lung cancer have been investigated in clinical trials, none has been shown to date to be effective in reducing lung cancer mortality [2], [3], [4], [5]. Low radiation dose helical computed tomography (LDCT), an advance in CT technology introduced during the mid 1990s, offers rapid image acquisition at a radiation dose substantially below that of standard CT [6]. Findings from a mass screening program in Japan and from the Early Lung Cancer Action Project (ELCAP), both reported in the late 1990s, demonstrated that LDCT could detect lung cancer in asymptomatic subjects with greater sensitivity than could chest X-ray [7], [8].
The Lung Screening Study (LSS) was designed as a pilot study to examine the feasibility of performing a large scale randomized lung cancer screening trial of LDCT versus single view chest X-ray (CXR). The design and the results of the baseline screening round of LSS have recently been published and show that the LSS was highly successful in recruiting and screening a relatively large number of eligible high risk subjects without recent past spiral CT use in a short period of time [9]. The success of the LSS led to the development and implementation of the ongoing National Lung Screening Trial (NLST), a multi-center trial that has randomized over 50,000 high risk subjects to either LDCT or CXR. Although the original design of the LSS specified only a baseline screen, it was later expanded to include a second (year one) screen. In this paper, we examine the results of the year one LSS screen in the LDCT and CXR arms, compare them to the results from the baseline round, and summarize all the screen detected and interval cases of lung cancer occurring during the study period.
Section snippets
Methods
The design of the Lung Screening Study is described in Gohagan et al. [9]. Briefly, the LSS was a pilot randomized trial of screening for lung cancer with LDCT versus chest X-ray (CXR). To be eligible, an individual had to be between 55 and 74 years old, have at least a 30 pack-year history of cigarette smoking, and be either a current smoker or a former smoker who quit within the last 10 years. Exclusion criteria included history of a spiral CT exam of the lungs or thorax in the previous 24
Results
A total of 1,660 eligible subjects were randomized to LDCT and 1,658 to CXR. Demographics and smoking history were similar across the two arms. A total of 59% were male, 68% were age 55–64 years (32%;age 65–74 years), and 58% were current (42% former) smokers; the median pack years of smoking was 54. Table 1 displays the year one compliance and positivity rates in each arm broken down by the baseline screening result. Overall compliance with screening at year one was 85.8% in the LDCT arm and
Discussion
We have reported here on the second and final round of screening in the LSS and on the cumulative lung cancer yield in the LSS. Compliance with screening at year one was 86% in the LDCT arm and 80% in the CXR arm; this compares to baseline compliance rates of 96% (LDCT) and 93% (CXR) [9]. The use of spiral CT outside of the trial for screening purposes by CXR arm subjects (cross-over contamination) continued to be low, with a rate reported here of 1.3% after the year one screen, as compared to
Conclusion
The success of the LSS paved the way for the current, randomized National Lung Screening Trial. NLST was designed and powered to answer the question of whether screening with spiral CT decreases lung cancer mortality, as compared to screening with chest X-ray. The findings reported here and elsewhere from the LSS may provide clues as to what to expect from the larger NLST in terms of compliance, screen positivity, diagnostic follow-up, and lung cancer yield.
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Writing Committee.