Quitting smoking improves lung cancer survivalEveryone knows that quitting smoking makes a huge difference to a person’s chance of developing lung cancer. But what about people who already have lung cancer? Does quitting make a difference if you’ve already developed the disease?

A team of researchers from Birmingham University, led by Dr Paul Aveyard, has reviewed all the current evidence, and concluded that the chances of surviving early-stage lung cancer are greater for people who stop smoking after they’re diagnosed than for people who carry on.

Aveyard’s team searched through many years’ worth of research and found 10 studies involving people who had either continued to smoke or given up after they’d been diagnosed. The studies measured a whole range of outcomes, such as how many people died during the study (of any cause), whether people developed different cancers as well as lung cancer, or whether their lung cancer came back after treatment.

Improving survival

Number-crunching the data from all of the studies, the researchers found that people with a type of lung cancer called ‘non-small cell’ lung cancer who continued to smoke were almost three times more likely to die during the study than people who stopped (with odds of almost 3 to 1). People with different type of lung cancer – small cell lung cancer – who continued smoking were nearly twice as likely to die as those who gave up (in this case, the odds were 1.86 to 1).

One study also looked at the risk of the cancer returning after treatment, and found that people who continued smoking were nearly twice as likely to have a recurrence as people who gave up. And continuing smokers with small cell lung cancer were over four times more likely to develop a second new cancer than quitters.

These differences had a stark impact on the number of people who survived for more than five years after diagnosis. The team estimated that for patients with early stage non-small cell lung cancer, 33 per cent of continuing smokers would survive for five years after diagnosis but for people who quit smoking, a massive 70 per cent would survive. For limited stage small cell lung cancer, 29 per cent of smokers and 63 per cent of quitters would survive five years.

Why is this happening?

It’s possible that quitting smoking improves cancer survival because people are less likely to die from other smoking-related diseases, like heart disease, stroke and chronic lung diseases. But when Aveyard calculated how many people would usually be expected to die from these other diseases, he found that most of the improvement in survival was actually down to a lower risk of dying specifically from cancer.

But it’s still not clear exactly how and why cigarette smoking affects a cancer’s progress. The authors put forward two possible explanations: that cancer-causing chemicals in tobacco smoke could be doing even more damage to people’s DNA and encouraging the cancer to progress; or that nicotine itself could be affecting the blood supply to the tumour and encouraging growth.

At the moment, it’s not clear whether either of these is the real reason (it could even be a combination of the two), but finding out could help to provide evidence to support the link between quitting and survival.

Early stage disease

In all but one of these studies, most of the patients involved had been diagnosed with early stage lung cancer, rather than with advanced disease. So although the research shows that quitting smoking is a good idea for people with early stage disease, at this stage it’s difficult to conclude what the story will be for people with advanced cancers.

Sadly, in the UK lung cancer is often diagnosed at a late stage, when survival is lower. That’s why we’re working through the National Awareness and Early Diagnosis Initiative (NAEDI) to try to promote early diagnosis of lung cancer. We’ve developed a video and information about lung cancer signs and symptoms, which you can see on our Spot Cancer Early site.

Giving up smoking is the best present you’ll ever give yourself. It will improve your health in the short and long term, and it’s worth giving up at any age, no matter how long you have smoked for. We’ve known for a long time that giving up before you become ill can reduce the risk of developing serious disease. But now there’s evidence that, even after a diagnosis of lung cancer, it’s still worth quitting.

Need support?

If you would like to give up smoking, there is lots of support available which has been proven to help you. The NHS smokefree site can help you to find the support that’s right for you. Much of this support is free, and smokers are four times more likely to quit successfully if they get professional support than if they try to go “cold-turkey”.

If you have questions about lung cancer, or giving up smoking, you can call our cancer information nurses on 0808 800 4040 (Monday to Friday, 9am-5pm).