Longitudinal Electronic Cigarette Use Among Patients Recently Diagnosed With Cancer Enrolled in a Smoking Cessation Trial

Abstract

Introduction

Many cancer patients who smoke report concurrent e-cigarette use. Using a mixed-methods approach, we aimed to (1) describe longitudinal e-cigarette use over 6 months after a cancer diagnosis and (2) assess the association between e-cigarette use and smoking cessation, among cancer patients in a smoking cessation trial.

Aims and Methods

Data were from a 2-site randomized controlled trial of Standard (brief counseling) versus Intensive treatment (sustained counseling plus smoking cessation medication) in individuals who smoke recently diagnosed with cancer. Participants (n = 303) reported e-cigarette use at baseline, 3 months, and 6 months. Biochemically-verified past 7-day cigarette abstinence was collected at 6 months. Qualitative interviews at 6 months explored factors related to e-cigarette use.

Results

E-cigarette use prevalence was highest between baseline and 3 months (16%) and declined over time. Participants using e-cigarettes at follow-up had higher baseline cigarette dependence and smoked more heavily. Multivariable analyses found no significant association between follow-up e-cigarette use and 6-month cigarette abstinence. E-cigarette use at follow-up was higher in the Standard versus Intensive treatment group (p = .003 and .001 at 3 and 6 mo, respectively). Smoking cessation and health concerns were primary reasons for using e-cigarettes.

Conclusions

Among individuals who smoke recently diagnosed with cancer and enrolled in a smoking cessation intervention trial, e-cigarette use during trial participation was not associated with smoking abstinence. Individuals who chose to use e-cigarettes were less likely to be receiving intensive cessation support as part of the trial. Further studies are needed to evaluate the association between e-cigarette use and smoking cessation in cancer patients.

Implications

E-cigarette use was not associated with cigarette abstinence at 6 months among adults who smoke recently diagnosed with cancer enrolled in a smoking cessation trial. Individuals with easier access to evidence-based smoking cessation treatment may be less likely to use e-cigarettes.

Introduction

The prevalence of electronic cigarette (e-cigarette) use among patients with cancer is increasing in the United States.^1,2 Among individuals who smoke recently diagnosed with cancer, we found that half had ever used e-cigarettes and 19% reported past 30-day e-cigarette use.³ Most of these individuals who smoke reported using e-cigarettes to try to quit smoking combustible cigarettes (cigarettes). Since continued cigarette smoking after a cancer diagnosis has clinically meaningful negative effects on cancer treatment complications and mortality^4,5 it is necessary to understand the association between e-cigarette use and smoking cessation in recently diagnosed patients.

A growing literature of randomized controlled trials in the general population suggests that e-cigarette use is effective for smoking cessation.^6–8 For example, a randomized trial among UK adults found that e-cigarettes were more effective than nicotine replacement therapy for smoking cessation, although 80% of participants in the e-cigarette group were still using e-cigarettes one year later (compared to 9% of participants in the nicotine replacement therapy group).⁷ A 2020 Cochrane review found that users of nicotine e-cigarettes had higher cigarette quit rates compared to users of nicotine replacement therapy (RR 1.69, 95% CI 1.25 to 2.27) and concluded that there is moderate certainty evidence that nicotinized e-cigarettes increase quit rates compared to e-cigarettes without nicotine and compared to NRT.⁹ Regardless, there is ongoing debate about whether e-cigarettes should be recommended for smoking cessation in the United States and concerns remain about unknown long-term health effects of e-cigarette use.¹⁰ In the two observational studies (only one of which was longitudinal) among patients with cancer, e-cigarette use has not been associated with increased smoking cessation,^11,12 although these studies were conducted several years ago and device characteristics and prevalence of use have evolved since that time. Taken together, very little research has investigated e-cigarette use and the impact on smoking cessation in cancer patients who smoke. Cancer patients who smoke are a medically and psychiatrically complex population. More research on e-cigarette use in this population is urgently needed to support efforts to tailor tobacco treatments in this group to promote quitting and reduce morbidity and mortality.

While e-cigarettes have generally been viewed as safer than combustible cigarettes,⁸ they have not been endorsed by leading cancer care organizations (eg, IASLC)¹³ and the 2019 outbreak of e-cigarette, or vaping, product use-associated lung injury (EVALI) raised additional concerns about the short-term safety of e-cigarettes.¹⁴ The EVALI outbreak has since been associated primarily with tetrahydrocannabinol (THC)-containing vaping products and vitamin E acetate.¹⁵ The long-term safety of e-cigarettes will likely depend on factors such as type of device used and duration of use. Taken together, it is important to understand both longitudinal cigarette and e-cigarette use patterns among cancer patients who use e-cigarettes.

To address these questions, we conducted a secondary analysis of longitudinal data from a randomized trial comparing intensive versus standard smoking cessation treatment among individuals who smoke recently diagnosed with cancer.¹⁶ In the present mixed-methods analysis, we quantitatively characterized e-cigarette use patterns over 6 months, evaluated smoking cessation outcomes among individuals who smoke who did and did not use e-cigarettes, and assessed e-cigarette use among participants randomized to intensive versus standard smoking cessation treatment during the trial (participants in the intensive treatment arm were more likely to be abstinent from cigarettes at 6 months).¹⁶ Qualitatively, we explored reasons for e-cigarette use and non-use across the study and patient discussions of e-cigarette use with their cancer clinicians as context for our quantitative findings. We hypothesized that participants receiving standard treatment (vs. intensive) would be more likely to use e-cigarettes during the trial.

Methods

We analyzed quantitative and qualitative data from the Smokefree Support Study, a two-site randomized controlled comparative effectiveness trial. The study protocol and reporting of main outcomes have been described previously.^16,17 Participants were enrolled from two NCI-designated Comprehensive Cancer Centers in the United States between November 2013 and July 2017. All participants were enrolled within the timeframe of 3 months of their cancer diagnosis or within 4 visits to the cancer center and were followed for 6 months. Participants were surveyed at baseline, 3 month, and 6 month timepoints; assessments began at enrollment start in 2013 and were completed by the end of February 2018. The study was approved by the Institutional Review Board at each study site.

Participants

Adults (>18 years old) were eligible for the study if they had a recent diagnosis of cancer (defined as within 3 months of diagnosis or 4 visits to the cancer center), smoked at least 1 cigarette in the past 30 days, and spoke either English or Spanish. Potentially eligible participants were identified through screening of cancer clinic schedules.

Intervention

Participants were randomized 1:1 to either Standard Treatment (ST) or Intensive Treatment (IT) delivered by trained and supervised tobacco treatment counselors. ST consisted of weekly brief telephone counseling for 4 weeks and smoking cessation medication treatment advice. IT consisted of brief weekly telephone counseling for 4 weeks, biweekly telephone counseling for 2 months, and monthly telephone counseling for 3 months. Participants in the IT arm received a choice of FDA-approved smoking cessation medication (nicotine replacement therapy, varenicline, or bupropion) at no cost for 12 weeks. Consistent with national guidelines for cancer patients (eg American Cancer Society), our smoking cessation counselors did not promote the use of e-cigarettes and instead encouraged participants to use FDA-approved smoking cessation treatments.¹⁸ For participants who were using e-cigarettes in the IT group, counselors shared potential risks of e-cigarette use with participants.

Measures

Quantitative Surveys

We defined baseline current e-cigarette use as any past 30-day e-cigarette use. At 3- and 6-month follow-ups, participants were asked whether they had used an e-cigarette in the past 3 months. We defined any e-cigarette use at follow-up as reporting e-cigarette use in the past 3 months at either 3-month or 6-month follow-up. At 3- and 6-month follow-ups, participants were also asked, “In the last 7 days, on how many days did you use an e-cigarette?”. We defined current e-cigarette use at 3 or 6 months as reporting e-cigarette use on 1 or more of the last 7 days.

The trial’s primary outcome was biochemically-verified past 7-day cigarette abstinence at 6 months. Abstinence was verified by urine cotinine <15 ng/mL or, for participants using nicotine replacement therapy or nicotine-containing e-cigarettes, expired air carbon monoxide <10 ppm.^19,20

Qualitative Exit Interviews

After the 6-month follow-up quantitative surveys, a random subset of participants (N = 72; ST, n = 32 and IT, n = 40) completed in-depth semi-structured individual interviews using a priori stratification criteria that included racial/ethnic minority, history of serious mental illness, and e-cigarette use. The interviews were conducted by study team investigators and asked about smoking and quitting behaviors, beliefs about FDA-approved smoking cessation medications, e-cigarette use, and stress and distress symptoms since joining the study. For e-cigarette use, participants were asked whether they were currently using e-cigarettes or were former or never users. Questions also probed about reasons for using and not using e-cigarettes based on current e-cigarette use status. All interviewees were asked about any discussions they may have had with their doctors about e-cigarettes. Interviews were conducted by telephone and lasted an average of 30–40 min. All interviews were audio-recorded and transcribed verbatim.

Analysis

Prevalence of current e-cigarette use at baseline, 3 months, and 6 months was examined using frequency distributions. The present analysis is limited to the n = 201/303 trial participants (66%) who provided data on e-cigarette use at follow-up. We compared characteristics of patients reporting any e-cigarette use at follow-up, that is reporting e-cigarette use in the past 3 months at either 3-month or 6-month follow-up, using chi-square tests and t tests. Prevalence of e-cigarette use at each timepoint by study arm (ST vs. IT) was compared using chi-square tests. For the outcome of biochemically-verified cigarette abstinence at 6 months, chi-square tests compared e-cigarette users to non-users, and analyses were further stratified by study arm. Univariable logistic regression was conducted to assess the association between e-cigarette use and smoking- and cancer-related covariates and biochemically-verified cigarette abstinence at 6 months. Multivariable logistic regression was performed controlling for demographic and social factors, as well as all other factors with p < 0.20 in univariable analyses (ie, study treatment group, age, sex, race, ethnicity, education, smoking cessation medication use; See Table 3 footnote). This p value was selected based on recommendations in the literature and evidence that more traditional p values (such as p < .05) can fail to identify important variables from univariate testing.^21–23 All quantitative analyses were done using Stata version 14 (StataCorp LLC, College Station, TX).

Table 3.

Biochemically verified Cigarette Abstinence at 6 Months

	% Abstinent from cigarettes at 6 months	OR (unadjusted)	aORa	aORb
Any e-cigarette use at follow-up
Yes (n = 47)	21% (n = 10)	0.43 (0.20–0.93)	0.50 (0.23–1.11)	0.59 (0.26–1.36)
No (n = 150)	39% (n = 58)	Ref.	Ref.	Ref.
Current e-cigarette use at 3 m
Yes (n = 18)	28% (n = 5)	0.73 (0.25–2.13)	0.88 (0.29–2.65)	0.88 (0.28–2.75)
No (n = 188)	35% (n = 65)	Ref.	Ref.	Ref.
Current e-cigarette use at 6 m
Yes (n = 22)	18% (n = 4)	0.36 (0.12–1.10)	0.42 (0.13–1.31)	0.47 (0.14–1.54)
No (n = 191)	38% (n = 73)	Ref.	Ref.	Ref.

Bolded values denote p < .05.

^aControlling for tobacco treatment study group.

^bControlling for tobacco treatment study group, age, sex, race, ethnicity, education, smoking cessation medication use.

For the qualitative analysis, interview transcripts were coded independently by three trained study staff using NVivo 11 (QSR International, Burlington, MA). An inductive approach to qualitative content analysis was used, beginning with open coding of the interview transcripts and further categorization of the codes into broader themes until thematic saturation was reached. High inter-coder agreement was reached with Kappa > 0.86.

Results

Quantitative Surveys

Of the 303 trial participants, 153 were randomized to the IT group and 150 to the ST group. The study total sample had a median age of 59 years, 56% (87/153) were female, 84% (127/153) identified as non-Hispanic White, 32% (50/153) had a high school education or less, and 60% (92/153) had a smoking-related tumor.¹⁶

The overall prevalence of past 30-day (current) e-cigarette use at baseline was 19% (56/302). At 3 months, 16% (35/213) of participants reported e-cigarette use in the past 3 months, and 10% (21/213) of participants reported past 7-day (current) e-cigarette use. Of the 10% of participants who were currently using e-cigarettes at 3 months (n = 21; 1 participant had missing data on cigarette abstinence at 3 months), 30% (n = 6/20) were completely abstinent from combustible cigarettes, while 70% (n = 14/20) were dual users of e-cigarettes and combustible cigarettes. At 6 months, 15% (33/217) of participants reported e-cigarette use in the past 3 months, and 10% (23/217) reported past 7-day (current) e-cigarette use. Of the 10% of participants who were currently using e-cigarettes at 6 months (n = 23; 1 participant had missing data on cigarette abstinence at 6 months), 18% (4/22) were completely abstinent from combustible cigarettes, while 82% (n = 18/22) were dual users of e-cigarettes and combustible cigarettes.

Baseline sociodemographic, tobacco use, and cancer-related characteristics of the sample by any e-cigarette use at follow-up are shown in Table 1 (n = 201 participants with data on follow-up e-cigarette use). There were no significant sociodemographic differences between participants who did and did not use e-cigarettes at follow-up. More participants who used any e-cigarettes at follow-up reporting smoking their first cigarette of the day within 30 min of waking, and they smoked more cigarettes per day at baseline than participants who did not use e-cigarettes at follow-up. A higher percentage of participants who reported e-cigarette use at follow-up had been diagnosed with a smoking-related tumor compared to participants who did not use e-cigarettes at follow-up (Table 1).

Table 1.

Characteristics of Study Population by E-cigarette Use at Follow-up

	Any e-cigarette use at follow-up (n = 50)	No e-cigarette use at follow-up (n = 151)	p
Age, mean (standard deviation)	57.8 (10.1)	59.6 (9.2)	.25
Female sex	56% (28)	60% (90)	.65
White race	94% (47)	87% (132)	.20
Hispanic ethnicity	2% (1)	3% (5)	.63
Education			.73
High school degree/GED or less	32% (16)	26% (40)
Some college	38% (19)	43% (65)
4-year degree or more	30% (15)	30% (46)
Smoking-related cancera	70% (35)	52% (79)	.03
Cancer stageb			.85
High	28% (14)	31% (47)
Low	68% (34)	67% (101)
Cancer tumor site			.30
Thoracic	30% (15)	25% (38)
Gastrointestinal (GI)	16% (8)	7% (11)
Breast	18% (9)	30% (46)
Genitourinary	12% (6)	21% (31)
Head and neck	16% (8)	9% (15)
Lymphoma	4% (2)	3% (4)
Gynecologic	2% (1)	2% (3)
Melanoma	2% (1)	2% (3)
Cigarettes per day	16.9 (13.2)	13.4 (8.5)	.03
First cigarette within 30 min of waking (nicotine dependence)	84% (42)	69% (102)	.04
Baseline e-cigarette use status			<.001
Never user	14% (7)	60% (91)
Former user	22% (11)	34% (51)
Current user	63% (31)	6% (9)
Tobacco Treatment Study Group
Intensive treatment	30% (15)	64% (96)	<.001
Standard treatment	70% (35)	36% (55)
Any FDA-approved medication use at follow-up	80% (35)	74% (112)	.47

Bolded values denote p < .05.

Tabled values represent column percentage (n) unless otherwise indicated.

^aCancer known to be caused by smoking: anal, bladder, cervical, colorectal, esophageal, gastric, head and neck, kidney, liver, lung, pancreatic, and small intestine^4,14).

^b5 patients did not have data available on their cancer stage.

Any e-cigarette use at follow-up was highest among participants reporting current e-cigarette use at baseline. Specifically, 78% (31/40) of participants reporting current e-cigarette use at baseline, 18% (11/62) of participants reporting former e-cigarette use at baseline, and 7% (7/98) of participants reporting never using e-cigarettes at baseline reported any e-cigarette use at follow-up. Longitudinal e-cigarette use patterns among baseline e-cigarette users and nonusers are shown in Table 2. Prevalence of e-cigarette use declined over time and this decline was only statistically significant from baseline to 3 mo for the intensive treatment group (p = .02).” Specifically, while 67% (24/36) of baseline current e-cigarette users and 11% (18/160) of baseline non-users of e-cigarettes reported using e-cigarettes between baseline and 3 months, respectively, prevalence of current e-cigarette use at 6 months was 39% (16/41) and 3.5% (6/173), respectively at 6-month follow-up.

Table 2.

Longitudinal E-cigarette Use Patterns

Among current users of e-cigarettes at baseline
	Total population		Standard treatment		Intensive treatment
	n/total	%	n/total	%	n/total	%
Any e-cigarette use after baseline	31/40	78	20/22	91	11/18	61
Any e-cigarette use between baseline and 3 months	24/36	67	16/19	84	8/17	47
Any e-cigarette use between 3 and 6 months	22/41	54	15/21	71	7/20	35
Current e-cigarette use at 3 months	15/36	42	11/19	58	4/17	24
Current e-cigarette use at 6 months	16/41	39	13/21	62	3/20	15
Among non-users of e-cigarettes at baseline
Any e-cigarette use after baseline	18/160	11	14/67	21	4/93	4
Any e-cigarette use between baseline and 3 months	11/177	6	10/79	13	1/98	1
Any e-cigarette use between 3 and 6 months	10/175	6	7/76	9	3/99	3
Current e-cigarette use at 3 months	6/176	3	5/78	6	1/98	1
Current e-cigarette use at 6 months	6/173	4	4/74	5	2/99	2

Participants who reported any e-cigarette use at follow-up were less likely to have biochemically-verified 6-month cigarette abstinence in bivariate analyses (p = 0.03), however, in multivariable analyses, there was no significant difference in 6-month abstinence between those who reported any e-cigarette use at follow-up and those who did not (Table 3).

Finally, to evaluate whether prevalence of e-cigarette use differed among participants in the two tobacco treatment groups, we assessed e-cigarette use by study arm (Figure 1). While there were no differences in e-cigarette use between the IT and ST groups at baseline, the prevalence of current e-cigarette use at both 3-month and 6-month follow-up was significantly higher among participants in the ST group (who received brief counseling and medication advice only) compared to participants in the IT group (who received sustained counseling and choice of smoking cessation medication at no cost). Participants in the ST arm had significantly higher odds of any e-cigarette use at follow-up compared to patients in the IT arm in both univariable analyses (OR 4.1, 95% CI 2.04 to 8.12) and multivariable analyses (aOR 4.31, 95% CI 2.04 to 9.07, controlling for demographics, cigarettes per day, nicotine dependence, and having a smoking-related tumor; data not shown in tables).

Figure 1.

Prevalence of current e-cigarette use at baseline, 3 months, and 6 months. Current e-cigarette use was defined as past-30 day use at baseline, and past-7 day use at 3 and 6 month follow-ups. The decrease seen in e-cigarette use prevalence within the Intensive Treatment group was statistically significant between baseline and 3 months (p = .02). No differences were observed in e-cigarette use over time between any timepoints within the Standard Treatment group.

Qualitative Interviews

Reasons for E-cigarette Use

Three primary themes emerged among current e-cigarette users for why they used e-cigarettes (Supplemental Table 1): (1) e-cigarettes were seen as a smoking cessation or reduction strategy, (2) perceiving e-cigarettes as a healthier nicotine/tobacco product than combustible cigarettes (eg, “There are some risks involved with it but…I think they’re negligible compared to the combustibles.”), and (3) e-cigarettes satisfying the conditioned behavior of smoking combustible cigarettes (eg, “e-cigarettes help because they look like a cigarette and you hold it like a cigarette”).

Reasons for Not Using E-cigarettes

Former e-cigarette users reported no longer using e-cigarettes because (Supplemental Table 1): (1) e-cigarettes did not help with quitting or cutting back on cigarette use (eg, dual use of e-cigarettes with cigarettes), (2) concern that the e-cigarette provided too much nicotine or other safety concerns (eg, “I couldn’t do it [use e-cig] because it was like one drag felt like you smoked a pack of cigarettes. I don’t recommend the e-cigarette. I think they should be banned.”), or (3) they did not enjoy of the products (eg, because of taste or smell).

Never e-cigarette users reported a variety of reasons for not trying the products including (Supplemental Table 1): (1) perception that e-cigarettes are similar in harms to smoking combustible cigarettes, (2) fear and safety concerns (“Well, because those e-cigarettes can be very dangerous, and I was already putting nicotine into me so why put more? I was trying to cut back on the nicotine, not make it worse”), (3) lack of access to e-cigarettes, (4) lack of knowledge about e-cigarettes (“I think I saw a headline or something that the jury was still out as to whether or not they were less harmful to you than normal cigarettes”), and (5) that e-cigarettes did not appear satisfying.

Conversations With Physicians About E-cigarettes

Some participants reported speaking to their physician about e-cigarette use, and most of these participants reported that their doctor did not support use due to (1) perception of harms or (2) lack of knowledge about harms and safety. Some participants perceived that their doctor viewed e-cigarettes as more harmful than combustible cigarettes (eg, “…the doctor told me, he says “I don’t even care if you go back to smoking, but you’d be better off than having those [e-cigs]. There’s no regulation, we don’t know what they put in there;” “I went to my thoracic surgeon..he said, you might has well smoke a cigarette because it’s [e-cigarettes] are worse for you than a cigarette”).

Discussion

Among people who smoke recently diagnosed with cancer participating in a smoking cessation trial, 25% reported at least some e-cigarette use during the trial. Over one-third of individuals who smoke, who reported e-cigarette use after trial enrollment, were not using e-cigarettes at baseline, and thus initiated e-cigarette use during the trial. E-cigarette use at follow-up was not associated with biochemically-verified smoking abstinence at 6 months.

E-cigarette use declined over the duration of the trial, and current use was lowest at 6 months follow-up. Furthermore, few participants began e-cigarette use during trial participation. At the time of trial enrollment, patients were recently diagnosed with cancer and beginning cancer treatment, which could have served as a strong impetus to try to quit smoking.²⁴ Smoking cessation is a common reason for e-cigarette use among cancer patients,^3,25 and e-cigarettes may have been used as part of a strategy to quit early, consistent with participants’ reports of reasons for use in the qualitative interviews. The decreasing e-cigarette use over the trial period may suggest initial experimentation with e-cigarettes that was not maintained over time. In qualitative interviews, although cutting back or quitting was the primary reason for e-cigarette use, participants who had formerly used e-cigarettes revealed that they didn’t find e-cigarettes helpful for quitting and/or that their doctor did not support e-cigarette use or recommend use due to safety concerns. Similar reasons for using and stopping e-cigarette use have been reported in other populations of adults.²⁶

In unadjusted analyses, e-cigarette use was negatively associated with 6-month cigarette abstinence, but this association was not significant after adjusting for other factors, in particular, treatment arm. We found that participants receiving standard smoking cessation support were significantly more likely to use e-cigarettes during the trial compared to participants receiving intensive treatment. This is likely due to the intensive treatment emphasis on use of FDA-approved smoking cessation treatments. This is similar to a study among recently hospitalized adult individuals who smoke in which participants receiving free smoking cessation treatment with medication and automated telephone calls for three months were less likely to use e-cigarettes compared to participants receiving treatment recommendations only.²⁷ These data suggest that ease of access to FDA-approved smoking cessation medications may affect whether a smoker chooses to use e-cigarettes when trying to quit smoking.

While e-cigarette use among study participants was self-selected, this analysis provides an observation of how cancer patients may be using e-cigarettes in the context of their quit attempts. Future studies should collect information on frequency of e-cigarette use, which is an important factor in understanding the association between e-cigarettes and smoking cessation.^28,29 Clinical trials of e-cigarettes should be conducted with cancer patients not able or willing to use FDA-approved cessation medications as some randomized trials have found cessation benefit in other populations.^7,30,31 Until further information about e-cigarette safety and efficacy for smoking cessation is available, individuals who smoke with cancer should be encouraged to use FDA-approved smoking cessation therapies such as combination short and long-acting nicotine replacement therapy, varenicline, and bupropion in their quit attempts.^13,32 In line with qualitative findings, in addition to recommending evidence-based cessation treatments, cancer clinicians should discuss the known and unknown risks and benefits of e-cigarettes with regard to quitting smoking in the context of cancer care. Given the prevalence of e-cigarette use among adult smoking individuals with cancer who were engaging in an attempt to quit in this study, it is important that clinicians caring for other clinical populations of adult smoking individuals, such individuals with other chronic medical conditions, assess for e-cigarette use during the course of quit attempts.

This study is subject to several limitations. First, as mentioned above, this was a secondary analysis of a randomized trial in which participants were not randomized to e-cigarette use, and therefore there is the potential for selection bias. Second, all e-cigarette use was self-reported and may be subject to recall bias/misreporting. Third, data are from patients recently diagnosed with cancer from two academic medical centers and may not be generalizable to cancer patients later in the course of their diagnosis or in different geographic locations. Additionally, there was little racial diversity in our sample which limits generalizability. Fourth, participants were not randomized to e-cigarette use in this trial, and participants who chose to use e-cigarettes differed from those who did not on several characteristics. Fifth, sample sizes for some subgroup analyses (eg study arm) were small. Sixth, there are a range of e-cigarette products on the market and we did not ask participants what specific types of e-cigarettes they used. More detailed measurement of device types should be collected in future studies. Finally, smoking cessation counselors actively encouraged use of evidence-based smoking cessation medications, which may have influenced whether participants chose to use e-cigarettes. Furthermore, some participants who used e-cigarettes in the IT arm were counseled on the potential risks of e-cigarette use, and this may have affected their decision to continue use. We were unable to assess the relationship between frequency and intensity of cigarette and e-cigarette use over time.

In this study of individuals who smoke recently diagnosed with cancer enrolled in a clinical trial, e-cigarette use during the course of trial participation decreased over time and was not associated with smoking abstinence at 6 months. Participants who used e-cigarettes appeared to have characteristics associated with greater difficulty quitting smoking and were less likely to be receiving intensive cessation support as part of the trial. Providers should assess for e-cigarette use in cancer patients receiving smoking cessation treatment, and promote use of evidence-based treatments to quit.

Supplementary Material

A Contributorship Form detailing each author’s specific involvement with this content, as well as any supplementary data, are available online at https://academic.oup.com/ntr.

Funding

This work was supported by the National Cancer Institute (R01CA166147 and K24CA197382). Dr. Kalkhoran’s work on this manuscript was supported by the National Heart, Lung, and Blood Institute (K23HL136854). The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Declaration of Interests

Drs. Kalkhoran, Rigotti, Park, and Ostroff have received royalties from UpToDate, Inc. Dr. Rigotti has been an unpaid consultant to Pfizer, Inc. and a paid consultant to Achieve Life Sciences. All other authors declare no potential conflicts of interest.

Data Availability

The data underlying this article will be shared on reasonable request to the corresponding author.