The Mayo Lung Project (MLP) was a clinical trial conducted between 1971 and 1983. It involved random assignment of male smokers to either a periodic (every 4-6 months) chest X-ray lung cancer screening program versus a usual care program that included the "treatment as usual" (TAU) recommendation to be screened yearly. The two trial arms then went through a prevalence screening, where 9,211 subjects were diagnosed as cancer-free and thus eligible for staying in the study. Those in the intervention arm then received periodic chest roentgenograms and three-day "pooled" sputum cytology studies thrice a year while lung-health questionnaires were delivered to both arms of the trial. The MLP results were mixed inasmuch as participants in the periodic screening program demonstrated longer case survival but worse lung cancer mortality as compared with those in the usual care program [
1‐
3].
Surprisingly, no attention has been paid to the smoking behavior of MLP participants, even though smoking status has been shown to be the most important predictor of lung cancer incidence and survival. This study examines the interaction between periodic lung cancer screening and smoking behavior reported in the MLP in order to better understand the behavioral contributors to observed outcomes.
It is well established that smoking cessation could significantly reduce smokers' lung cancer mortality [
4]. Further, we know that if individuals are alerted to avoidable fatal risks, they often take steps to reduce that risk [
5]. Therefore, it is reasonable to infer that undergoing periodic lung cancer screening, which serves as a constant reminder of the deadly outcome of cigarette smoking, could stimulate smoking cessation among current smokers [
5]. Behavioral evidence from various chronic diseases has suggested that episodic medical occasions that heighten the patient's awareness of disease risk, often called "the teachable moment"[
6‐
8], can significantly motivate the patient to reduce or abandon the risk behavior[
9‐
13]. For example, smokers who went through heart-related surgeries maintained an abstinence rate of 48% at 5-year follow-up, a level that no known interventions have achieved [
10]. However, other than a single-arm study that showed an increase in smoking cessation efforts after people attended lung cancer screening [
6], there has been insufficient documented evidence of lung cancer screening's causal impact on smoking cessation among those screened. Now that the policy debate over mandating a periodic CT screening of smokers has attracted widespread academic interest and media attention [
14,
15], the question of whether the screening intervention could lead to smoking cessation has become timely. This paper examines two aspects of smoking behavior observed during the MLP: the current smoking status (whether one smoked any cigarette in a given year) and the amount of cigarettes smoked per day.