For smokers, the risk of developing lung cancer falls if they quit the habit, however it will never be as low as the risk that applies to someone who has never smoked, Irish doctors have said.

According to Dr Jane Kleinerova and Dr Dermot O'Callaghan of the Mater Hospital in Dublin, lung cancer currently affects some 1.8 million people worldwide and is responsible for 1.6 million deaths annually.

It is the fourth most common cancer in Ireland, with around 2,000 new cases here every year.

"The disease is now the most common cause of cancer death among both men and women in this country. The principal risk factor is cigarette smoking, being causative in approximately 90% of cases," the doctors explained.

They noted that in people who quit and stay off cigarettes, ‘the risk falls for about 15 years following cessation, though never returns to that of a never-smoker and remains twice that of life-long non-smokers'.

Other risk factors for the disease can include genetics, chronic lung diseases such as COPD (chronic obstructive pulmonary disease) and environmental factors, such as the inhalation of asbestos fibres or radon gas.

The doctors noted that the majority of patients who present with lung cancer ‘already have advanced disease' and the most common symptom is cough, which affects up to three in four people.

They added that around 85% of patients have symptoms of the disease when they first present and ‘a timely diagnosis and accurate staging of patients with suspected lung cancer is critical in order that appropriate therapy can be administered'.

Dr Kleinerova is a specialist clinical registrar in respiratory medicine and Dr O'Callaghan is a consultant respiratory physician. They made their comments in the journal, Hospital Doctor of Ireland.