E-cigarettes do not appear to help cancer patients quit smoking, according to a new study.

The health dangers of smoking are well-documented and it is widely acknowledged that anyone diagnosed with cancer should be advised to quit the habit. US scientists decided to look at e-cigarettes specifically in relation to cancer, to see whether they helped or hindered attempts to quit smoking.

E-cigarettes are battery-powered devices designed to supply nicotine through inhaled water vapour. They are currently at the centre of a major debate, with some people stating that they can help smokers to quit the habit and others insisting that they are potentially harmful to health.

The study involved over 1,000 cancer patients who smoked and who were enrolled in a tobacco treatment programme between 2012 and 2013.

The scientists found that during this time, the use of e-cigarettes jumped from 10% to 38%.

They also found that at the start of the study, those who already used e-cigarettes in addition to traditional cigarettes tended to be more dependent on nicotine than those who only smoked traditional cigarettes.

E-cigarette users had also attempted to quit smoking more often than non-users, and they were more likely to be diagnosed with lung, head or neck cancers.

When the participants were followed up, the scientists found that e-cigarette users were just as likely as non-users to still be smoking.

The scientists from New York believe that the findings raise doubts about the role of e-cigarettes in helping cancer patients to quit smoking and called for more studies in this area.

"Consistent with recent observations of increased e-cigarette use in the general population, our findings illustrate that e-cigarette use among tobacco-dependent cancer patients has increased within the past two years. Controlled research is needed to evaluate the potential harms and benefits of e-cigarettes as a potential cessation approach for cancer patients," they said.

They added that in the meantime, doctors should ‘advise all smokers to quit smoking traditional combustible cigarettes, encourage use of approved cessation medications, refer patients for smoking cessation counseling, and provide education about the potential risks and lack of known benefits of long-term e-cigarette use'.

Details of these findings are published in the journal, CANCER.