Are E-Cigarettes a Dangerous Alternative to Traditional Cigarettes?

A Conversation With Graham W. Warren, MD, PhD

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Several studies published earlier this year present preliminary but compelling evidence that electronic cigarettes, also known as e-cigarettes, which deliver nicotine through aerosols without burning tobacco, may pose serious health consequences to users, including cardiovascular disease and cancer. Although the studies concede that more in-depth research needs to be conducted to determine their long-term safety, the consensus of the studies is that the vapor produced by e-cigarettes is not harmless water vapor but instead contains the same toxic chemicals found in smoke from traditional cigarettes.

Graham W. Warren, MD, PhD

Graham W. Warren, MD, PhD

One of the studies by Moon-shong Tang and colleagues found that mice exposed to e-cigarette vapor experienced DNA damage in the lung, bladder, and heart as well as reduction in their DNA-repair functions and lung proteins. Similar damage was also found in cultured human lung and bladder cells that had been exposed to e-cigarette vapor for the equivalent of 10 years. The DNA damage and reduction in DNA-repair functions caused by e-cigarette vapor, concluded the researchers, “might contribute to human lung and bladder cancer as well as to heart disease.”1

A comprehensive study by the National Academies of Sciences, Engineering, and Medicine, also published this year, which examined data from over 800 peer-reviewed scientific studies on the health effects of e-cigarettes, found that these devices have a biologic effect in humans. For example, the exposure of nicotine in e-cigarettes can be comparable to the amount from combustible tobacco cigarettes. In addition, although most of the chemical flavorings used in e-cigarettes, such as tobacco, menthol, and coffee, are generally regarded as safe by the U.S. Food and Drug Administration (FDA), they have not been studied for safety when inhaled in an e-cigarette. The report also found insufficient evidence from randomized controlled trials about the effectiveness of e-cigarette use as a smoking cessation aid compared with no treatment or FDA-approved smoking cessation treatments.2 (See sidebar on -“Tobacco Cessation Resources”.)

The findings present a new dilemma for oncologists looking to wean their patients from traditional cigarettes to a seemingly less harmful form of nicotine replacement found in e-cigarettes. In a landmark 2014 Surgeon General report, which was the first to explicitly evaluate the effects of smoking on cancer treatment, current smoking by patients with cancer and cancer survivors increased overall mortality by a median of 51% and cancer-related mortality by a median of 61%.3 The report also found a causal relationship between cigarette smoking and the risk for second primary cancer and poorer response to treatment, as well as an increased risk for treatment-related toxicities, according to Graham W. Warren, MD, PhD, Vice Chairman for Research in Radiation Oncology and the Department of Cell and Molecular Pharmacology and Experimental Therapeutics at the Hollings Cancer Center, Medical University of South Carolina in Charleston, and Past-Chair of ASCO’s Tobacco Cessation and Control Subcommittee.

In 2015, ASCO published a joint policy statement with the American Association for Cancer Research calling for additional research on e-cigarettes to assess their health impacts and determine their role in aiding smoking cessation. The statement also supports the federal, state, and local regulations of e-cigarettes and recommends that manufacturers register with the FDA, report all product ingredients, and prohibit youth-oriented marketing and sales.4

The ASCO Post talked with Dr. Warren about how oncologists can advise their patients who smoke to quit, the health risks of switching to e-cigarettes, and the potential effect of e-cigarettes on cancer cells.

Helping Patients to Quit Smoking

According to the National Cancer Institute, in 2016, 13% of cancer survivors aged 18 and older continued to smoke after a cancer diagnosis.5 How can oncologists counsel their patients who smoke on the benefits of quitting and help them to stop smoking?

This is a multifaceted problem. First, it is very important for oncologists to clearly realize the known adverse effects of smoking on cancer treatment and that addressing tobacco smoking with patients is now recognized as a standard part of cancer care. Both oncologists and patients need to understand that.

We have to be honest with patients when talking with them about the risks of continuing to smoke after a cancer diagnosis and explain how smoking decreases the effectiveness of cancer treatment.
— Graham W. Warren, MD, PhD

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Second, we have to figure out the best mechanisms to help patients to quit smoking, because one-sized solutions do not fit all. In many cases, the availability of effective evidence-based cessation programs depends on an institution’s resources and patients’ access to those resources. Ideally, all patients should have access to dedicated tobacco cessation support at their institution, and all patients should have information on how to access smoking cessation quitlines in their location. Across the United States, patients can call the toll-free quitline (1-800-quit-now or 1-800-784-8669), which will then connect them to their state quitline. We also have to be honest with patients when talking with them about the risks of continuing to smoke after a cancer diagnosis and explain how smoking decreases the effectiveness of cancer treatment. We must help patients realize that although we are here to help them quit, ultimately, it is a choice they have to make. We should reinforce that message and support patients in their efforts to quit and congratulate them on their progress at each office visit.

It is important to remember that smoking is an extremely difficult habit to break. Although many patients do try to quit smoking, the stressors associated with quitting, including withdrawal symptoms, and with a cancer diagnosis can make it tough.

Questioning Safety of E-Cigarettes

E-cigarettes were thought to be a safe alternative to smoking conventional cigarettes, but studies are showing that they contain the same cancer-causing chemicals. How safe are e-cigarettes for cancer survivors concerned about a cancer recurrence?

We don’t have clear information yet on the health effects of e-cigarettes on patients with cancer or on cancer cells. It is an area that needs investigation and will take a while for us to truly understand the effects of e-cigarettes in the context of cancer care—and on the health of the general population over the long term.

However, what we can definitively say is that continued smoking causes adverse outcomes in patients with cancer. I don’t want my patients to smoke. I want them to use FDA-approved smoking cessation medications, such as varenicline tartrate (Chantix), nicotine replacement therapy, or bupropion, to help them stop smoking. We don’t have clear evidence or recommendations on the use of e-cigarettes to help people quit smoking, and it will take time to generate solid data in this area. In the meantime, as clinicians, we are still faced with new cancer diagnoses every day, and these patients need guidance now, not years down the road after better data are available.

We don’t have clear evidence or recommendations on the use of e-cigarettes to help people quit smoking, and it will take time to generate solid data in this area.
— Graham W. Warren, MD, PhD

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Although we know from the study by the National Academies of Sciences, Engineering, and Medicine that harmful chemicals are present in e-cigarettes and that the amount of nicotine in some e-cigarette products is comparable to the level found in combustible tobacco cigarettes,2 it is unclear how they compare with continued tobacco smoking. It is also unclear how these chemicals will interact with chemotherapy, radiotherapy, or other types of cancer treatment. These questions will only be answered with time. 

For now, I tell patients they need to quit smoking and make sure every patient discusses tobacco use and access to evidence-based tobacco cessation support. I’m inclined to favor e-cigarettes over smoking because of the proven adverse effects of tobacco smoking, but my patients also realize the limited evidence we have about the long-term health effects of e-cigarettes. They also recognize that we can’t wait to start their cancer treatment until all the data are generated.


One severely understudied question we have to investigate is the effect of e-cigarette ingredients on cancer cells compared with cancer cells that are exposed to combustible cigarette smoke. Are e-cigarettes better, worse, or the same as smoking traditional cigarettes? We don’t know how the various vaporized components of e-cigarettes, such as nicotine, propylene glycol, glycerin, and other additives, interact with cancer treatment. These components have the potential to alter the biology of cells, tumor growth, and the cytotoxic effects of cancer treatment.

These questions require evaluation in clinical trials, but I anticipate that the constituents of e-cigarettes will be shown to have unique cellular and health effects on patients with cancer and the general population. ■

DISCLOSURE: Dr. Warren reported no conflicts of interest.


1. Lee HW, Park SH, Weng MW, et al: E-cigarette smoke damages DNA and reduces repair activity in mouse lung, heart, and bladder as well as in human lung and bladder cells. Proc Natl Acad Sci U S A 115:E1560-E1569, 2018.

2. The National Academies of Sciences, Engineering, and Medicine: Consensus Study Report: Public Health Consequences of E-Cigarettes. January 2018. Available at Accessed August 30, 2018.

3. U.S. Department of Health & Human Services Centers: The Health Consequences of Smoking—50 Years of Progress: A Report of the Surgeon General. National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2014. Available at Accessed August 30, 2018.

4. Brandon TH, Goniewicz ML, Hanna NH, et al: Electronic nicotine delivery systems: A policy statement from the American Association for Cancer Research and the American Society of Clinical Oncology. J Clin Oncol 33:952-963, 2015.

5. National Cancer Institute: Cancer Trends Progress Report: Cancer Survivors and Smoking. Available at Accessed August 30, 2018.