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Examining whether lung screening changes risk perceptions: National Lung Screening Trial participants at 1-year follow-up†
Article first published online: 20 DEC 2012
Copyright © 2012 American Cancer Society
Volume 119, Issue 7, pages 1306–1313, 1 April 2013
How to Cite
Park, E. R., Gareen, I. F., Jain, A., Ostroff, J. S., Duan, F., Sicks, J. D., Rakowski, W., Diefenbach, M. and Rigotti, N. A. (2013), Examining whether lung screening changes risk perceptions: National Lung Screening Trial participants at 1-year follow-up. Cancer, 119: 1306–1313. doi: 10.1002/cncr.27925
The authors wish to thank Dr. Deni Aberle, without whose support the study would not have been possible. We are also appreciative of the efforts of ACRIN staff members Irene Mahon and Maria Oh, as well as Kelly Hyland and Joanna Streck at MGH. Lastly, we are very grateful for the assistance and approval of the eight ACRIN/NLST participating Principal Investigators, site coordinators, and staff at the Brown University Center for Statistical Sciences.
Presented at the 17th Annual Meeting of the Society for Research on Nicotine and Tobacco; February 16-19, 2011; Toronto, Ontario, Canada.
- Issue published online: 18 MAR 2013
- Article first published online: 20 DEC 2012
- Manuscript Accepted: 30 OCT 2012
- Manuscript Revised: 24 OCT 2012
- Manuscript Received: 10 SEP 2012
- lung screening;
- risk perception;
The National Lung Screening Trial (NLST) research team reported reduced lung cancer mortality among current and former smokers with a minimum 30 pack-year history who were screened with spiral computed tomography scans compared with chest x-rays. The objectives of the current study were to examine, at 1-year follow-up: 1) risk perceptions of lung cancer and smoking-related diseases and behavior change determinants, 2) whether changes in risk perceptions differed by baseline screening result; and 3) whether changes in risk perceptions affected smoking behavior.
A 25-item risk perception questionnaire was administered to a subset of participants at 8 American College of Radiology Imaging Network/NLST sites before initial and 1-year follow-up screens. Items assessed risk perceptions of lung cancer and smoking-related diseases, cognitive and emotional determinants of behavior change, and knowledge of smoking risks.
Among 430 NLST participants (mean age, 61.0 years; 55.6% men; 91.9% white), half were current smokers at baseline. Overall, risk perceptions and associated cognitive and emotional determinants of behavior change did not change significantly from prescreen trial enrollment to 1-year follow-up and did not differ significantly by screening test result. Changes in risk perceptions were not associated with changes in smoking status (9.7% of participants quit, and 6.6% relapsed) at 1-year follow-up.
Lung screening did not change participants' risk perceptions of lung cancer or smoking-related disease. A negative screening test, which was the most common screening result, did not appear to decrease risk perceptions nor provide false reassurance to smokers. Cancer 2013. © 2012 American Cancer Society.
Each year in the United States, more than 220,000 individuals are diagnosed with lung cancer, and 87% of lung cancer deaths are attributable to smoking.1 Smokers are over 10 times more likely to develop lung cancer compared with nonsmokers.2, 3 The prognosis for patients with lung cancer is poor, largely because only 15% of patients with lung cancer are diagnosed at an early stage of disease.1 The National Lung Screening Trial (NLST) compared lung cancer mortality rates among high-risk current and former smokers who had a minimum 30 pack-year smoking history and found that low-dose computed tomography (CT) screening reduced lung cancer mortality by 20% relative to screening with chest x-ray.4 The National Comprehensive Cancer Network (NCCN) recently released guidelines recommending annual low-dose helical CT screening for high-risk individuals.5
There is significant apprehension about widespread use of lung CT. Bach and colleagues, in a recent systematic review, concluded that CT screening significantly reduced lung cancer mortality but that uncertainty exists surrounding its potential harms.6 The cost-effectiveness of CT screening is estimated to be $126,000 per quality-adjusted life year (QALY) for current smokers and $169,000 per QALY for former smokers,7 which is largely the result of the substantial number of false positives, which result in downstream costs and risks associated with additional work-ups. In the NLST, over 3 rounds of screening, 39.1% of low-dose helical CT screens and 16.0% of chest x-ray screens produced at least 1 positive result, and >90% of these were deemed false positives.4 Some have argued that funds for lung cancer prevention would be better spent on proven primary prevention efforts rather than screening.8-10
The NCCN revised lung screening guidelines explicitly include smoking cessation counseling,5 which could add a meaningful risk reduction component. Even at the time of a lung cancer diagnosis, quitting smoking can improve treatment efficacy.11-13 Undergoing screening may enhance abstinence motivation and quitting among current smokers and may prevent relapse among former smokers, especially if the screening result is not normal. Alternatively, a negative CT screening test may falsely reassure smokers and make them less motivated to quit smoking.14 The effect of undergoing CT screening on smoking behaviors remains inconclusive; some studies have demonstrated higher than expected quit rates, and others have demonstrated little or no change in smoking.14-16
Thus, lung screening, and its result, may influence smokers' intentions and motivation to quit,14, 17, 18 and changes in risk perception may mediate cessation motivation and behavior change.19 Park and colleagues demonstrated that, before their initial screen, NLST participants' risk perceptions were associated with their behavioral intentions. Specifically, among current smokers, risk perceptions correspondingly increased with intentions to quit smoking; among former smokers, risk perceptions were lower among those who were committed to remain abstinent. Individuals' perceptions of their risk of lung cancer and other smoking-related diseases (SRDs) may be affected by screening or its results; recent studies suggest that lung screen results change short-term lung cancer risk perceptions by increasing risk perceptions for individuals who have non-negative tests.20, 21
The sustained effect of lung screening on risk perceptions and, in turn, changes in smoking behavior, is unclear. Thus, the objective of the current study was to assess the effects of lung screening and test results on risk perceptions that may underlie smoking behavior changes 1 year after an initial lung screen. We hypothesized that the process of undergoing screening would increase risk and, thus, promote abstinence, particularly among participants who receive a positive baseline test result. A theoretically based risk perception questionnaire22 was administered to a subset of NLST participants before their initial (baseline) and 1-year screens, providing an opportunity to assess changes in risk perception and smoking behavior and the impact of baseline screen results on these constructs. It is our hope that this study will contribute to past research on risk perceptions in the context of lung screening, in that: 1) our findings are based on a comprehensive risk measure that examines both lung and SRD risk perceptions, 2) we include an examination of cognitive and emotional behavior change constructs, and 3) we present longitudinal data on risk perception changes and smoking outcomes.
MATERIALS AND METHODS
This longitudinal study examined changes in lung cancer and SRD risk perceptions among NLST participants and the effects of a change in risk perceptions and other theoretically based behavior change determinants on smoking behaviors from baseline to 1-year follow-up. The NLST is a collaboration between American College of Radiology Imaging Network (ACRIN) and the National Cancer Institute Lung Screening Study.4 This study is registered with clinicaltrials.gov (clinical trials identification number NCT00047385; trial registry CDR0000257938).
Cohort and Data Collection
At the time of trial recruitment, participants were ages 55 to 74 years, current or former (quit within 15 years) smokers with a history of 30 pack-years minimum, and had no history of lung cancer. Twenty-three ACRIN study sites participated in the NLST/ACRIN arm of NLST, and 8 sites participated in the substudy. From December 2003 to March 2004, participants at the 8 sites were offered the opportunity to complete the risk perception substudy questionnaire at the time of baseline and 1-year follow-up screens. At baseline, 630 participants completed the questionnaire; of these, 430 participants (68%) also completed the questionnaire before their 1-year follow-up screen. Nearly 90% of participants who completed the ACRIN/NLST follow-up forms also completed the risk perception questionnaire. Baseline smoking status and recruitment site differed significantly for non-completers versus completers, and significantly more non-completers were current smokers.
Baseline sociodemographic, medical, and smoking history variables
The trial baseline questionnaire23 included measures of sociodemographics, medical history (family history of lung cancer, personal history of cancer or SRD), smoking history (smoking status [“Do you smoke now?”], number of years smoked, number of years quit, average number of cigarettes smoked per day, and nicotine dependence during “the time period when you smoked the most” [Fagerstrom Test for Nicotine Dependence24]; score range, 0-10; low to high dependence). Baseline screen results were categorized as 1) negative, defined as having no major abnormalities; 2) significant abnormalities not suspicious for lung cancer; or 3) positive, defined as revealing a nodule or other abnormality suspicious for lung cancer.
Follow-up smoking outcome
One-year follow-up questionnaires23 were used to collect information on smoking status (“Do you now smoke cigarettes [1 or more cigarettes per week]?”). It has been established that self-reported smoking status is a reliable means of assessing smoking status among participants undergoing lung screening.25
Risk perception substudy questionnaire
Details on the questionnaire were published previously.22 In brief, using behavioral change constructs from the Health Belief Model,26 the Precaution Adoption Process Model,27 the Self-Regulation Model,28 and the work of Kreuter and Strecher,29 we developed a questionnaire.22
The Smoking Risk Perceptions Scale.
Ten items assessed individual's personal (individual) risk and comparative risk (related to others) for lung cancer and other SRDs. Because lung screening may detect lung cancer and/or an SRD, risk perceptions for lung cancer and SRDs were analyzed separately with two 5-item scales. To assess lung cancer and SRD risk, 2 questions assessed the likelihood (“very unlikely” to “very likely”) and danger (“strongly disagree” to “strongly agree”) of developing lung cancer and SRD; and 3 questions, using the referent groups average individuals, others of the same age and sex, and other former/current smokers, assessed comparative risk (lung risk 5-item scale: α = .87; 70% variance; SRD risk 5-item scale: α = .86; 66% variance).
Cognitive and emotional determinants of smoking cessation.
Self-efficacy was measured by 1 question about confidence to quit smoking/remain quit (5-point Likert scale from “not at all” confident to “extremely” confident). Perceived benefits of quitting smoking/staying quit were measured by 3 questions about the benefits of quitting in terms of decreasing the risk for lung cancer and other SRDs and increasing life expectancy (4-point Likert scale from “not at all” beneficial to “very much” beneficial); these items were combined to create a composite score (range, 3-12; α = .89). Perceived severity was assessed by 4 questions about the health consequences and severity of lung cancer and other SRDs (5-point Likert scale from “not at all” severe to “extremely” severe); these items were combined to create a composite score (range, 4-16; α = .85). Perceived benefits of lung screening were assessed by 2 questions about the curability and benefits of lung cancer detected by screening (4-point Likert scale from “very few” benefits to “most” benefits; range, 1-4). Worry about lung cancer and other SRDs was assessed by 4 questions about intensity (4-point Likert scale from “not at all” intense to “extremely” intense) and frequency of worry (4-point Likert scale from “not at all” to “all of the time”); items were combined to create a composite score (range, 4-16; α = .89).
Knowledge of smoking risks was assessed by 2 questions asking participants to quantify a smoker's risk of developing lung cancer (“A smoker who smokes 1 pack of cigarettes a day is at how many more times risk of developing lung cancer compared with a nonsmoker?” and “Among 100 smokers, how many will get lung cancer because they smoke?”).
All statistical analyses were conducted using the SAS/STAT statistical software package (version 9.2; SAS Institute Inc., Cary, NC). Complete case analyses were run. To ensure that the substudy participants were balanced across randomization arms, we compared baseline characteristics by study arm. Baseline findings demonstrated that former and current smokers differed significantly on sociodemographic factors, smoking characteristics, and risk perceptions,22 so all analyses were conducted separately by smoking status. Thus, differences between study arms and baseline smoking status groups were assessed using chi-square tests/Fisher exact tests for categoric variables and 2-sample t tests for continuous variables separately for former and current smokers. Mean differences and 95% confidence intervals were calculated to compare baseline to 1-year changes in risk perceptions, cognitive and emotional behavioral change determinant constructs, and knowledge. One-way analyses of variance were conducted separately for former smokers and current smokers to assess changes in lung cancer and SRD risk perceptions across the categories of baseline screen results. Separate logistic regression models for current smokers and former smokers examined the effect of baseline to 1-year follow-up changes in risk perceptions for lung cancer and SRDs on 1-year smoking status; unadjusted and adjusted analyses (adjusting for study arm, baseline test result, sex, and race) were conducted.
Approximately 50% of participants were current smokers (Table 1). Baseline participant characteristics and risk perception outcomes did not differ significantly by study arm. Current and former smokers differed significantly on many sociodemographic and smoking characteristics. Former smokers had been quit for an average of nearly 7 years; however, former smokers reported a higher average number of cigarettes per day (29.77) compared with current smokers (26.27). Baseline screen results were negative for 82.49% of current smokers and 87.32% of former smokers, negative for lung cancer but positive for other lung abnormalities in 7.83% of current smokers and 3.29% of former smokers, and positive for suspected lung cancer in 9.68% of current smokers and 9.39% of former smokers. At the 1-year follow-up screen, no participants had a confirmed lung cancer diagnosis.
|No. of Participants (%)|
|Characteristic||Current Smokers, N = 217||Former Smokers, N = 213||P|
|Age: Mean±SD, y||60.30±4.40||61.80±5.24||.001|
|Men||106 (48.85)||133 (62.44)||.01|
|Women||111 (51.15)||80 (37.56)|
|<High school||15 (6.91)||12 (5.63)||.25|
|High school graduate/GED||75 (34.56)||54 (25.35)|
|Posthigh school training, some college||70 (32.26)||79 (37.09)|
|>College||50 (23.04)||61 (28.64)|
|Other/unknown||7 (3.23)||7 (3.29)|
|<$15,000||30 (13.82)||13 (6.10)||< .01|
|$15,000-34,999||58 (26.73)||40 (18.78)|
|35,000-64,999||55 (25.35)||71 (33.33)|
|$65,000 and above||40 (18.43)||30 (14.08)|
|Unknown||34 (15.67)||59 (27.70)|
|Married/living as married||122 (56.22)||154 (72.30)||< .01|
|Widowed/divorced/separated||85 (39.17)||50 (23.47)|
|Never married||10 (4.61)||8 (3.76)|
|Unknown||0 (0)||1 (0.47)|
|White||192 (88.48)||203 (95.31)||.02|
|Black or African American||23 (10.60)||8 (3.76)|
|Other||2 (0.92)||2 (0.94)|
|No. of years smoking: Mean±SD||42.15±6.07||37.50±7.08||< .01|
|No. of years quit: Mean±SD||NA||6.88±4.85|
|Average no. of cigarettes/d: Mean±SD||26.27±9.21||29.77±12.24||< .01|
|No. of 24-h quit attempts in the past y|
|Unknown or NA||21 (9.68)||NA|
|FTND score: Mean±SDa||5.41±2.23||5.20±2.61||.38|
|Had family history of lung cancer||50 (23.04)||39 (18.31)||.23|
|Had personal history of cancer||22 (10.14)||23 (10.80)||.82|
|Had personal history of SRD||57 (26.27)||44 (20.66)||.17|
|Baseline screening results|
|Negative||179 (82.49)||186 (87.32)||.12|
|Significant for nonlung cancer abnormalities||17 (7.83)||7 (3.29)|
|Positive||21 (9.68)||20 (9.39)|
Changes in Risk Perception and Other Determinants of Smoking Cessation
Risk perceptions of lung cancer and SRDs are listed in Table 2. Lung cancer risk perceptions did not change significantly from baseline to 1-year follow-up (current smokers: mean, 17.91 vs 18.09 at baseline and follow-up, respectively; former smokers: mean, 16.28 at baseline and follow-up). Similarly, SRD risk perceptions did not change over time (current smokers: mean, 18.52 vs 18.76 at baseline and follow-up, respectively; former smokers: mean, 16.76 vs 16.86, respectively). In terms of determinants of smoking behavior change, cognitive and emotional constructs (perceived confidence, perceived disease severity, perceived benefits of quitting and lung screening, and worry) and knowledge of smoking risks did not change. The only factor that changed significantly was an elevated sense of the perceived benefits of quitting smoking among former smokers (mean change, 0.43; 95% confidence interval [CI], 0.20-0.67).
|Current Smokers at Baseline||Former Smokers at Baseline|
|Mean±SD Score||Mean±SD Score|
|Measure (Score Range)||No.a||Baseline||1 Year||Change||95% CI||No.a||Baseline||1 Year||Change||95% CI|
|Lung cancer risk (5-25)||215||17.91±3.93||18.09±3.85||0.18±0.21||−0.23, 0.59||212||16.28± 3.80||16.28±3.96||0.00±0.22||−0.43, 0.43|
|SRD risk (5-25)||215||18.52±4.06||18.76±4.05||0.25±0.25||−0.25, 0.74||212||16.76±4.00||16.86±4.29||0.09±0.26||−0.43, 0.62|
|Cognitive and emotional constructs|
|Perceived benefits of quitting smoking (3-12)||207||9.11±2.10||9.00±2.12||−0.09±0.15||−0.39, 0.21||205||9.75±1.99||10.23±1.82||0.43±0.12||0.20, 0.67|
|Confidence to quit smoking/ remain quit (1-5)||203||2.71±1.12||2.84±1.21||0.13±0.08||−0.04, 0.29||192||4.66±0.74||4.56±0.85||−0.09±0.06||−0.22, 0.03|
|Perceived severity of lung cancer and SRDs (4-20)||193||18.24±2.12||18.26±1.98||−0.01±0.13||−0.26, 0.24||196||18.55±1.70||18.28±2.11||−0.22±0.13||−0.47, 0.03|
|Perceived benefits of lung screening (1-5)||207||4.83±1.44||4.88±1.45||0.05±0.09||−0.14, 0.23||207||4.94±1.41||4.91±1.36||−0.02±0.12||−0.25, 0.20|
|Worry about lung cancer and SRDs (4-16)||192||10.09±2.84||10.23±2.81||0.14±0.16||−0.18, 0.46||200||9.04±2.72||9.13±2.52||0.10±0.16||−0.21, 0.40|
|Knowledge of smoking risks|
|Percentage of smokers who will get lung cancer (0%-100%)||184||37.23±23.39||36.58±21.97||−0.65±1.32||−3.25, 1.95||194||40.82±22.54||42.16±22.27||1.34±1.67||−1.95, 4.63|
|One-pack/d smokers' risk of developing lung cancer (1-5)b||207||3.04±1.08||3.06±1.11||0.02±0.07||−0.11, 0.16||204||3.17±0.99||3.26±0.96||0.10±0.08||−0.05, 0.25|
Changes in Risk Perception by Lung Screen Results
Mean changes in risk perception from baseline to 1 year follow-up across baseline smoking status and baseline screening results are listed in Table 3. The change in current and former smokers' risk perceptions of lung cancer did not differ significantly with regard to baseline screening test results (mean change, 0.17 and −0.08, respectively [negative]; 0.71 and 0.86, respectively [significant for nonlung abnormalities]; and −0.14 and 0.40, respectively [positive]). Similarly, the change in current and former smokers' risk perceptions of SRDs also did not differ significantly with regard to baseline screening test results (mean change, 0.25 and −0.01, respectively [negative]; 0.41 and 2.00, respectively [significant for nonlung abnormalities]; and 0.10 and 0.40, respectively [positive]).
|Baseline Screening Results: Mean Change (95% CI)|
|Current Smokers||Negative, N = 177||Significant for Non-lung Cancer Abnormalities, N = 17||Positive, N = 21||P|
|Changes in lung cancer risk||0.17 (−0.29, 0.63)||0.71 (−0.83, 2.25)||−0.14 (−1.45, 1.16)||.69|
|Changes in SRD risk||0.25 (−0.30, 0.80)||0.41 (−1.10, 1.92)||0.10 (−1.74, 1.93)||.97|
|Baseline Screening Results: Mean Change (95% CI)|
|Former Smokers||Negative, N = 185||Significant for Non-lung Cancer Abnormalities, N = 7||Positive, N = 20||P|
|Changes in lung cancer risk||−0.08 (−0.53, 0.38)||0.86 (−1.73, 3.44)||0.40 (−1.14, 1.94)||.62|
|Changes in SRD risk||−0.01 (−0.56, 0.54)||2.00 (−2.47, 6.47)||0.40 (−1.61, 2.41)||.37|
Changes in Risk Perception As Predictors of Smoking Status at 1-Year Follow-Up
Changes in smoking status were observed from baseline to 1-year follow-up among participants who had a known smoking status at the 1-year follow-up screen; 9.7% of baseline current smokers reported quitting smoking, and 6.6% of baseline former smokers reported smoking resumption (data not shown). The data listed in Table 4 indicate that, among current smokers at baseline, smoking status at 1 year was not significantly associated with changes in risk perceptions of lung cancer (odds ratio [OR], 1.09; 95% CI, 0.93-1.26) or SRDs (OR, 1.05; 95% CI, 0.93-1.19) Among former smokers at baseline, smoking status at 1 year was not significantly associated with changes in risk perceptions of lung cancer (OR, 1.07; 95% CI, 0.90-1.28) or SRDs (OR, 0.98; 95% CI, 0.85-1.13).
|Modeling Continued Smoking||OR (95% CI)|
|Current smokers at baseline, n = 215|
|Changes in lung cancer risk perceptions||1.09 (0.93, 1.26)|
|Changes in SRD risk perceptions||1.05 (0.93, 1.19)|
|Modeling Relapse||OR (95% CI)|
|Former smokers at baseline, n = 212|
|Change in lung cancer risk perceptions||1.07 (0.90, 1.28)|
|Changes in SRD risk perceptions||0.98 (0.85, 1.13)|
In this longitudinal observational study of a subset of NLST participants who were followed for 1 year after their initial lung screen, we examined the impact of lung screening on perceived lung cancer risks and SRD risks and how changes in risk perceptions affected smoking behavior. In a subset of NLST participants, we conclude that undergoing screening, per se, did not have a significant impact on risk perceptions or sustained smoking behavior change.
Overall, risk perceptions for lung cancer and SRDs did not change at 1 year after lung screening. Our findings were similar to work conducted by Vierikko et al30 and Sinicrope et al,20 who determined that there were no significant changes in perceived lung cancer risk by 6 to 12 months after a lung cancer screening test. Sinicrope et al also reported that perceived lung cancer risk rose 1 month after the screening. Therefore, it is possible that there may have been an alteration in risk perception immediately after screening; however, if this is so, then our results indicate that this elevation is not sustained. Indeed, essentially no theoretically based determinants of smoking behavior change or knowledge were altered significantly with the exception of an elevated sense of the perceived benefits of quitting smoking among former smokers.
The 1-year follow-up self-reported quit rates (9.7% for current smokers at baseline) were somewhat higher than general population annual quit rates31; however, this is to be expected, because participants who enroll in screening trials are highly motivated to quit smoking and maintain abstinence.32, 33 In our current study, quit rates among current smokers at baseline and relapse rates among former smokers at baseline were relatively similar to the rates reported in recent screening studies.17, 32, 34
It is noteworthy that a negative initial screen did not appear to decrease current or former smokers' risk perceptions, indicating that a negative test does not provide false reassurance. This is very important, because, in real-world clinical settings, most lung screen results will be negative. These findings are concordant with recent research examining the effect of repeated negative scans on smoking behaviors. Townsend and colleagues reported that, over a 3-year period, repeated positive scans were associated with increased rates of smoking cessation.14 Similarly, Anderson and colleagues reported that, over a 6-year period, consistently negative scans were not associated with a lower likelihood of prolonged abstinence among smokers or a higher likelihood of relapse to smoking among former smokers.16
Some study limitations must be noted. First, the generalizability of these results is limited by a racially homogenous group of individuals who elected to participate in a screening trial at the 8 sites that participated in this substudy. Individuals who pursue screening based on a physician recommendation are likely to differ; indeed, individuals who have participated in lung screening studies have reported higher levels of risk perceptions33, 35 and quitting motivation.32 Second, we were not able to collect data on risk perceptions immediately after lung screening to determine whether there were short-term, transient changes in these outcomes. Regardless, our results indicate that, had there been any proximal changes, they were not sustained. Finally, we were likely underpowered to be able to detect significant differences in risk perceptions by baseline screen test result.
In summary, it appears that undergoing lung cancer screening, by itself, does not modify risk or other underlying determinants of changes in smoking behavior. At the initial screening, risk perceptions were associated with smoking intentions;22 however, at the 1-year follow-up assessment, risk perceptions were not predictive of smoking behavior change. We cannot rely on the screening itself to alter risk; rather, we need to intervene to leverage high-risk individuals' intentions to quit smoking. Given the high cost of screening, which increases if cessation rates are unaffected by screening, it is critical that tobacco treatment is integrated into the screening process.
This project was funded by a grant from the American Cancer Society's Mentored Research Scholar Award (MRSG-005-05-CPPB), the ACRIN/NLST Trial (U01 CA79778 S2), and a NHLBI Midcareer Investigator Award in Patient-Oriented Research (#K24-HL04440).
CONFLICT OF INTEREST DISCLOSURES
Dr. Rigotti works as an unpaid consultant for Pfizer and Alere Wellbeing. She previously received funding from Nabi Biopharmaceuticals and royalties from work published in UptoDate.
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- 5National Comprehensive Cancer Network (NCCN). NCCN Clinical Practice Guidelines in Oncology: Lung Cancer Screening. Fort Washington, PA: National Comprehensive Cancer Network; 2012.
- 23American College of Radiology Imaging Network. Protocol 6654 data forms. Philadelphia, PA: American College of Radiology Imaging Network; 2011. Available at: http://www.acrin.org/protocolsummarytable/protocol6654/6654Dataforms.aspx. Accessed November 17, 2011.
- 26Historical origins of the health belief model. Health Educ Monogr. 1974; 2: 328-335..
- 31Centers for Disease Control and Prevention (CDC). Cigarette smoking among adults—United States, 2007. MMWR Morb Mortal Wkly Rep. 2008; 57: 1221-1226.