Factors Associated with Smoking Cessation of Participants in the National Lung Cancer Screening Program in Korea
Article information
Abstract
Purpose
Smoking cessation interventions for participants in lung cancer screening are essential for increasing the effectiveness of screening to reduce lung cancer mortality. This study aimed to investigate the factors that lead to smoking cessation after lung cancer screening.
Materials and Methods
The Korean National Lung Cancer Screening (KNLCS) Satisfaction Survey was conducted from 2021 to 2022 with approximately 1,000 samples per year among participants in KNLCS targeting 30 or more pack-year smokers. Factors associated with smoking cessation were analyzed based on the survey.
Results
Among 1,525 current smokers in the survey participants, 728 (47.7%) received screening result counseling from physician after screening and showed significantly higher smoking cessation rate than non-counseling participants (odds ratio [OR], 2.17; 95% confidence interval [CI], 1.27 to 3.70). The participants who considered the counseling helpful were more likely to quit smoking (OR, 3.53; 95% CI, 2.00 to 6.22) and to reduce smoking amount (OR, 2.05; 95% CI, 1.54 to 2.71). Similarly, those who received physicians’ active recommendations to quit smoking were likely to quit smoking (OR, 2.20; 95% CI, 1.25 to 3.87) and to decrease smoking amount (OR, 1.30; 95% CI, 1.00 to 1.68). In contrast, participants who had no abnormal findings from screening tended to have no significant change in smoking status despite the physicians’ active recommendations to quit smoking.
Conclusion
Physicians’ active recommendations and effective counseling to quit smoking could be a key factor in increasing smoking cessation among lung cancer screening participants. Further research should be conducted to develop more effective strategies for smoking cessation to participants without abnormal findings in lung cancer screening.
Introduction
Lung cancer is currently the leading cause of cancer-related deaths in both males and females worldwide [1,2]. The Global Cancer Observatory of the International Agency for Research on Cancer estimated approximately 1.8 million deaths worldwide were due to lung cancer, accounting for the highest proportion of cancer-related deaths in men (22.7%) and the second highest in women (13.6%) [3]. Notably, Eastern Asia has one of the highest lung cancer incidence rates per 100,000 people, with 51.4% among men and 28.4% among women, respectively [3,4]. In South Korea, Statistics Korea reported that lung cancer was responsible for the highest proportion of cancer-related deaths, with 18,902 deaths (22.9%) recorded in 2021 [5].
The Korean National Lung Cancer Screening (KNLCS) program was initiated in August 2019. Using low-dose computed tomography (LDCT), the screening targets high-risk smokers aged between 54 and 74 years with a smoking history of at least 30 pack-years. Following screening, the screening result reports are sent to the participants by mail or email within two weeks. Additionally, the lung cancer screening participants can receive in-person counseling regarding the screening results and smoking cessation by physicians in the screening hospitals.
The objective of lung cancer screening with LDCT is to detect patients in the early stages of lung cancer when effective treatment is still possible, thereby reducing lung cancer mortality [6,7]. However, lung cancer screening itself might serve as “a license to smoke” in screening participants if they receive a negative result from screening [6,8,9]. If participants interpret negative results from lung cancer screening as permission to continue smoking, it could lead to various health issues associated with smoking, including an increased risk of developing lung cancer [10]. A possible “license-to-smoke” effect might eliminate any beneficial mortality reduction effect of lung cancer screening [6,9]. Therefore, lung cancer screening should require a systematic intervention to educate participants about the harmful effects of smoking and motivate them to quit smoking after screening [11].
Smoking is the leading risk factor for lung cancer and is responsible for 80% to 90% of lung cancer deaths [12]. Chemicals in tobacco smoke hinder the normal cleaning process of the lungs to remove harmful particles and prevent lung cells from repairing damaged DNA [13], thereby increasing the risk of various lung diseases, including lung cancer [14]. When one quits smoking, the risk of lung cancer starts to decrease [15]. After 10-15 years of quitting smoking, the risk of lung cancer is approximately half that of someone who continues to smoke [16]. Furthermore, smoking cessation can slow lung cancer progression and significantly reduce mortality [17].
Although smoking is a leading cause of premature death worldwide, it is notably preventable [18]. A smoking cessation intervention for smokers who participate in lung cancer screening is essential to increase screening effectiveness to reduce lung cancer mortality. Importantly, participation in lung cancer screening could serve as a teachable moment for smoking cessation [10]. Hence, from the beginning, the national lung cancer screening program in South Korea has systematically provided counseling on screening results and smoking cessation to screening participants by physicians in the screening hospitals.
To date, various factors that might lead to smoking cessation in the general population have been reported. However, the predictors of smoking cessation in participants who have already undergone a lung cancer screening program should be investigated more precisely [19]. Therefore, the current study aimed to analyze the factors associated with smoking cessation after participation in the national lung cancer screening program in South Korea.
Materials and Methods
The data used in this study were obtained from the KNLCS Satisfaction Survey involving KNLCS participants who were aged 54-74 years and have 30 or more pack-year smoking history. It is an annual cross-sectional telephone survey conducted by the National Cancer Center of the Republic of Korea, and approximately 1,000 respondents are randomly sampled each year. The survey was aimed to evaluate understanding of screening results, smoking cessation after screening, and satisfaction of the participants in KNLCS after obtaining agreement of survey participation.
The study data were combined with the survey results from 2021 to 2022, and the total number of survey participants was 1,924 (N2021=924, N2022=1,000). Among them, we excluded those who had already quit smoking at the time of participation in the lung cancer screening (n=340) to estimate the net effects of predictors on smoking cessation. Participants who did not receive screening results (n=58) or had missing responses (n=1) were also excluded. Overall, the current study analyzed 1,525 survey respondents in total (Fig. 1).
Flowchart of the study participants for investigating smoking cessation after lung cancer screening.
This study investigated not only the respondents’ success in smoking cessation but also related factors, including decrease in their smoking amount and increase in their willingness to quit smoking. Initially, to assess the respondents’ success in smoking cessation, they were asked about the changes in smoking status after lung cancer screening. The responses for change in smoking status were as follows: “quitted smoking after screening,” “smoke less than before,” “no change in smoking amount,” “smoke more than before,” “alternative cigarette use,” or “others.” We classified those who answered “quitted smoking after screening” as a “success in smoking cessation” group, and those who did not as a “no success” group. Secondly, “decrease in smoking” included the participants who answered either “quitted smoking after screening,” or “smoking less than before” from the above options. Finally, the participants were asked about their change in willingness to quit smoking after participating in the lung cancer screening, and the responses were as follows: “increased willingness,” “decreased willingness,” or “no change.” We classified those who answered that they had increased willingness to quit smoking as “willingness” in smoking cessation group, and those who did not as “no willingness” in smoking cessation group.
The independent variables in this study were participation in screening result counseling (yes or no), lung cancer screening results (having abnormal findings or not), understanding of screening result reports (easy, neutral, hard), attempt to quit smoking within 1 year (yes or no), smoking history (more than 40 pack-years or less), and sociodemographic factors, including sex, age, educational level, income level, marital status and residence. The responses regarding income level were as follows: “≤ 1.99 million Korean won (KRW),” “2.00-3.99 million KRW,” “≥ 4.00 million KRW,” and “Refusal to respond.” The KRW was converted to US dollars (USD) using the exchange rate on December 19, 2023 (1 USD=1,308.25 KRW).
Additionally, participants were asked about their attempts to quit smoking within the past year with the question: “Have you attempted to quit smoking in the past year?”. They could respond with “yes” or “no.” For abnormal findings, we asked: “Have you been informed about any abnormal findings in your screening report?” with responses of “yes” or “no.” Finally, to assess their “understanding of screening result report”, we asked “How easy was it for you to understand the results and recommendations in your screening report?” The response options were “very easy”, “easy”, “neutral”, “hard”, “very hard.” Participants who chose “very easy” and “easy” were classified as “easy” group, while those who chose “hard” and “very hard” were classified as “hard” group.
Participation in screening result counseling was sub-grouped based on the helpfulness of counseling for smoking cessation and the activeness of physicians’ recommendations to quit smoking during lung cancer screening result counseling, both of which were measured using a 5-point Likert scale. Participants who reported that the screening result counseling was “very helpful” or “helpful” for them to quit smoking were classified as “helpful” group, and those who responded as “neutral,” “not so helpful,” or “not helpful at all” were classified as “not helpful” group. Similarly, those who answered that the physician “very actively” or “actively” recommended them to quit smoking, were classified as “active” group, and those who answered “neutral,” “not so active,” or “not active at all” were classified as “not active” group.
Chi-square test and multivariable logistic regression analysis were used to statistically analyze the data. However, to examine the association between participation in result counseling and success in smoking cessation among respondents with abnormal findings, Fisher’s exact test and multivariable Firth’s logistic regression were used to mitigate analytical biases arising from small sample sizes, rare events, and separation.
The general characteristics of the samples were analyzed using frequencies and proportions. Multivariate logistic regression analyses were performed to analyze the factors associated with smoking cessation in the participants of the national lung cancer screening program by adjusting for relevant variables. The results of logistic regression analysis were reported as odds ratios (OR) and confidence intervals (CI). All statistical analyses were performed using STATA MP ver. 18.0 (StataCorp LLC).
Results
Among the 1,525 participants in the study, most were men (96.9%, n=1,478), aged ≥ 65 years (42.7%, n=651), had less than high school education (75.1%, n=1,146), with monthly income ≤ $1,520 (46.7%, n=712), and lived in a city (82.8%, n=1,263). Those who had ≥ 40 pack-years were 49.0% (n=748), those who attempted to quit smoking within 1 year were 39.7% (n=606), those who had abnormal findings from screening were 23.5% (n=358), and those who easily understood screening result reports were 63.9% (n=975).
Overall, 47.7% (n=728) of the 1,525 participants participated in the screening result counseling. The proportion of participants who considered the counseling helpful was 24.2% (n=369), and those who received physicians’ active recommendations to quit smoking in counseling were 35.0% (n=534). Additional sociodemographic and screening results are presented in Table 1, and participants’ characteristics stratified by abnormal findings are shown in S1 Table.
General characteristics of the study population
After screening, 5.3% (n=81) of the participants who were current smokers quit smoking, 27.0% (n=411) smoke less than before lung cancer screening, 65.2% (n=995) had no change in smoking amount, 1.0% (n=16) smoke more than before the screening, 1.1% (n=17) changed to use alternative cigarettes, and 0.3% (n=5) reported others (Fig. 2). The rates of success in smoking cessation, decrease in smoking, and willingness to quit smoking were significantly higher in participants who received screening result counseling than in non-participants (p < 0.001, p=0.006, and p=0.029, respectively).
Change in smoking status after lung cancer screening. a)Alternative cigarette use included e-cigarettes and heated tobacco products.
Results of the multivariate logistic regression analysis are shown in Table 2. Participation in counseling was associated with a higher probability of quitting smoking (OR, 2.17; 95% CI, 1.27 to 3.70). In addition, participants who were more than 65 years old were more likely to decrease smoking (65-69 years: OR, 1.49; 95% CI, 1.03 to 2.17; over 70 years: OR, 1.70; 95% CI, 1.14 to 2.53) after screening, than those who were younger.
Factors associated with smoking cessation in lung cancer screening participants analyzed by multivariable logistic regression
Participants with ≥ 40 pack-years were associated with lower probability of decrease in smoking (OR, 0.46; 95% CI, 0.36 to 0.58), and reduced willingness to quit smoking (OR, 0.62; 95% CI, 0.50 to 0.78) than those with < 40 pack-years. However, the participants who attempted to quit smoking within 1 year were significantly higher in the likelihood to quit smoking (OR, 7.57; 95% CI, 4.15 to 13.78), decreasing smoking amount (OR, 2.29; 95% CI, 1.82 to 2.89), and willingness to quit smoking (OR, 2.47; 95% CI, 1.99 to 3.08) than those who did not attempt to. Additionally, when abnormal screening results were found, participants had increased odds of smoking cessation (OR, 3.11; 95% CI, 1.90 to 5.09), decreasing smoking amount (OR, 2.12; 95% CI, 1.62 to 2.78), and willingness to quit smoking (OR, 2.48; 95% CI, 1.90 to 3.25).
Subsequently, subgroup analyses were conducted based on the participants’ self-evaluation of the screening result counseling (Table 3). Non-participation in result counseling was set as the reference group. Participants who reported the counseling as helpful to quit smoking, were associated with significantly higher probability of smoking cessation (OR, 3.53; 95% CI, 2.00 to 6.22), decrease in smoking (OR, 2.05; 95% CI, 1.54 to 2.71), and willingness to quit smoking (OR, 1.89; 95% CI, 1.43 to 2.51). Oppositely, those who reported the counseling to be not helpful had decreased odds of reduction in smoking (OR, 0.59; 95% CI, 0.43 to 0.81), and lesser willingness to quit smoking (OR, 0.57; 95% CI, 0.43 to 0.76). When participants received physicians’ active recommendations to quit smoking during counseling, they were more likely to quit smoking (OR, 2.20; 95% CI, 1.25 to 3.87), or at least reduce smoking (OR, 1.30; 95% CI, 1.00 to 1.68).
Results of subgroup analysis of factors associated with smoking cessation and physician’s attitude in lung cancer screening result counseling
Finally, we analyzed the factors associated with smoking cessation by combination with lung cancer screening results and physicians’ attitudes during counseling on screening results (Table 4). Among the participants with abnormal findings, participation in result counseling was strongly associated with smoking cessation (OR, 4.87; 95% CI, 1.68 to 14.18) and decrease in smoking (OR, 1.74; 95% CI, 1.04 to 2.92). When participants with abnormal findings reported the counseling to be helpful to quit smoking, or received physicians’ active recommendations to quit smoking during the counseling, each factor showed highly strong association with smoking cessation (helpfulness: OR, 8.41; 95% CI, 2.78 to 25.50; activeness: OR, 6.01; 95% CI, 2.02 to 17.91), decrease in smoking amount (helpfulness: OR, 3.10; 95% CI, 1.72 to 5.59; activeness: OR, 1.98; 95% CI, 1.15 to 3.40), and willingness to quit smoking (helpfulness: OR, 3.29; 95% CI, 1.73 to 6.25; activeness: OR, 1.83; 95% CI, 1.05 to 3.18).
Subgroup analysis of factors associated with smoking cessation and physician’s attitude in lung cancer screening result counseling by having abnormal findings or not
On the other hand, participants without abnormal findings tended to have no significant relationship with changes in smoking status after participating in screening result counseling. Physicians’ counseling to the participants who had no abnormal findings from lung cancer may lead to a slight increase in smoking cessation rates, although this increase is not statistically significant (OR, 1.39; 95% CI, 0.71 to 2.73). Furthermore, there was no significant change observed in the smoking habits of participants without abnormal findings, in decreasing their smoking amounts (OR, 1.03; 95% CI, 0.79 to 1.35), and increasing their willingness to quit smoking (OR, 0.94; 95% CI, 0.73 to 1.21), even though they participated in result counseling. More specifically, when those without abnormal findings reported the counseling as helpful to quit smoking, the smoking cessation rate increased, though not significantly (OR, 1.86; 95% CI, 0.87 to 3.97). Smoking cessation (OR, 0.98; 95% CI, 0.44 to 2.18), decreased smoking amount (OR, 1.13; 95% CI, 0.83 to 1.52) and increased willingness to quit smoking (OR, 1.00; 95% CI, 0.76 to 1.32) did not change significantly despite the physicians’ active recommendations to quit smoking.
Discussion
This study provided evidence that lung cancer screening along with screening result counseling by a physicians could be effective for participants to quit smoking after participating in lung cancer screening. Furthermore, helpful counseling and active recommendations by physicians to quit smoking can significantly increase willingness and behavior to smoking cessation among lung cancer screening participants.
To date, different results have been reported regarding the effects of various smoking cessation interventions on lung cancer screening participants. Telephone-based smoking cessation counseling after participating in lung cancer screening did not significantly increase the 12-month cessation rates compared to only written information [20]. In addition, there was no statistically significant difference in 7-day point prevalence quit rates or advancement in motivational readiness to stop smoking between the self-help material group and the internet-based resource group in a lung cancer screening population [21].
In contrast, a systematic review and meta-analysis indicated that in-person counseling and pharmacotherapy interventions after lung cancer screening could significantly increase the odds of smoking abstinence at 12 months, although electronic-/web-based and telephone counseling did not [22]. Similarly, a previous study had demonstrated that quitting attempts prompted by health professionals’ advice are more likely to involve gradual reduction of smoking amounts and use of evidence-based treatment [23]. In particular, physicians’ advice to stop smoking, despite being brief, can significantly increase people’s willingness to quit smoking [24].
The results of the present study are consistent with those of the previous studies. In the KNLCS, physicians provided participants in-person counseling on screening results and smoking cessation by explaining screening findings including lung nodules, emphysema and fibrotic changes could be caused by smoking. Of course, physicians also explained the risk of lung cancer by smoking. If the smokers who participated in lung cancer screening asked for help to quit, then physicians prescribed pharmacotherapy or gave them information on community smoking cessation programs.
Supportive and encouraging messages from physicians could motivate lung cancer screening participants to quit smoking [25]. A previous study based on systematic review had indicated that physicians’ intensive, personalized, and multimodal smoking cessation interventions for lung cancer screening participants could be the most influential in changing their smoking behaviors [8]. In this study, we analyzed the participants’ smoking status after screening, based on their screening results. When participants with abnormal findings either received helpful screening result counseling or received physicians’ active recommendations to quit smoking, each showed a strong relationship with their smoking status.
In contrast, participants without abnormal findings were not predominantly associated with smoking status changes, despite the helpfulness of counseling in smoking cessation and active recommendations from physicians to quit. Previous studies already reported that an abnormal screening result was significantly associated with participants’ readiness to quit smoking, whereas a negative result was associated with their becoming less ready to quit smoking [10,26]. In this respect, lung cancer screening could bestow a ‘license to smoke’ on participants with negative results [6,8,9]. Therefore, further research should be conducted to elaborate on strategies for screening result counseling by physicians to change the smoking behaviors of participants without any abnormal finding.
Finally, the findings of our study showed that the participants’ attempt to quit smoking could eventually lead them to do so, which was consistent with previous studies. Participants with higher pack-years were less likely to indicate an interest in quitting, since pack-years are related to nicotine dependence [10,27]. Moreover, as the number of quitting attempts within the past 12 months increased, the intention to quit smoking increased, which indicated that failure to stop smoking did not deter them from quitting smoking out of frustration [28]. Age of the participants was also found to be a predictor of smoking cessation after lung cancer screening, similar to a previous study, indicating that as age increases, the probability of continued smoking decreases [29].
Our study has several limitations. First, only participants’ self-reports of changes in smoking status were considered in this study. According to previous studies, self-reported smoking status can be questioned based on its validity [30,31]. Future research should consider using biomarkers, such as cotinine and exhaled carbon monoxide, to verify participants’ smoking status.
Second, this study did not track the participants’ smoking status over a long term. The smoking cessation process can vary and is often difficult to define. A previous study had demonstrated that individuals who smoked attempted to quit smoking more than 30 times before successfully quitting it for more than 1 year [32]. Participants’ recurrent relapse of smoking could be inevitable before the long-term success of smoking cessation. Therefore, dynamic observations would be necessary to verify the results.
Third, we analyzed two years of cross-sectional data and confirmed the association between the variables. However, the demonstration of an association does not necessarily prove a causal relationship. Furthermore, there is a possibility for self-selection bias since participants with a strong intent to quit smoking may be more likely to engage in counseling, because national lung cancer screening system in Korea, the decision to participate in screening result counseling is based on the participant’s choice. In our study, we sub-grouped the results based on the detailed content of the result counseling and whether participants received abnormal results. This self-selection bias might systematically overestimate our findings to some extent, but it is consistently meaningful in that the content of counseling such as physician’s active recommendation, and helpfulness of counseling could be differently associated participants’ smoking status.
Fourth, to ensure reliable results, we employed Fisher’s exact test and Firth’s logistic regression to address small sample sizes in the analysis of success in smoking cessation among respondents who had abnormal findings. These statistical adjustments show that active recommendations of smoking cessation by physicians significantly increased the success in smoking cessation. However, further research with larger sample sizes and long-term follow-ups is needed.
Finally, survey questions regarding screening result counseling could be necessarily subject to recall bias, because participants who successfully quitted smoking might be more likely to report positively on the counseling and physician’s recommendations. However, previous research found that patients report the experience of smoking cessation counseling in the hospital more accurately than physicians do, and it was the only report that predicts a quit attempt [33]. Furthermore, while other methods such as video-based observation can be used to conduct future research, these methods might complicate the research process due to technical requirements and confidentiality and privacy aspects [34].
Despite the limitations, the strengths of this study should be noted. None of the earlier studies had investigated the effect of screening result counseling on participants’ smoking cessation at the national level. We used randomly sampled data to generalize the findings for all the KNLCS participants. Moreover, very few studies have statistically analyzed the effect of counseling in lung cancer screening participants using a multivariate model including participation in lung cancer screening and sociodemographic factors. Finally, the effect of counseling was analyzed in multiple dimensions based on the participants’ subjective evaluations as well as the types of assistance provided from the screening result counseling.
By providing participants with appropriate smoking cessation interventions, lung cancer screening could become a teachable moment and not a license to smoke [10,35,36]. Our study demonstrated that counseling by physicians, regarding the screening results, could be a key factor in smoking cessation interventions for participants in lung cancer screening. Further studies would need to be conducted regarding the strategies of screening result counseling for participants with negative results. These important findings can be used as a baseline for the development of more effective smoking cessation interventions for lung cancer screening.
Electronic Supplementary Material
Supplementary materials are available at Cancer Research and Treatment website (https://www.e-crt.org).
Notes
Ethical Statement
The study was reviewed and approved by the Institutional Review Board (IRB) of National Cancer Center, Korea (approval number NCC2023-0297) in October 2023. Written informed consent was obtained before screening participation, and verbal consent was obtained over the telephone during the survey.
Author Contributions
Conceived and designed the analysis: Yoon NY, Kim Y.
Collected the data: Seo M, Lee N, Kim Y.
Contributed data or analysis tools: Yoon NY, Kim Y.
Performed the analysis: Yoon NY.
Wrote the paper: Yoon NY, Kim Y.
Contributed to critical revision of the manuscript for important intellectual content: Yoon NY, Seo M, Lee N, Kim Y.
Supervision: Kim Y.
Conflicts of Interest
Conflict of interest relevant to this article was not reported.
Funding
This work was supported in part by grants from the National R&D Program for Cancer Control and National Health Promotion Fund, Ministry of Health and Welfare, Republic of Korea [grant number NCC-2360080-1]; and the National Cancer Center, Republic of Korea [grant number NCC-2210810-2].