Lung cancer: Signs and symptoms to look out for
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Health experts in the US estimate as many as 20 percent of lung cancer patients who died in 2018 – about 30,000 people – have never smoked in their lives. Cigarette smoking is the leading risk factor in the UK and US, accounting for 70 to 80 percent of all lung cancer cases. And yet, people who have never touched a cigarette or have smoked less than 100 throughout their lives are not immune to the life-changing diagnosis.
Second-hand smoke, pollution and exposure to certain chemicals and radioactive gases can all increase the risk of developing lung tumours.
But the good news is a team of researchers at the Washington University School of Medicine in St Louis, US, may have found a solution to the problem.
According to a new report published on Thursday, between 78 and 92 percent of lung cancers in so-called never-smokers can be treated with drugs already approved by the US Foods and Drug Administration (FDA).
The study was published in the Journal of Clinical Oncology.
Health experts described nonsmokers as people who don’t presently smoke but may have smoked 100 or so cigarettes in the past.
Never-smokers, on the other hand, have never smoked or have smoked less than cigarettes.
And it appears as though smokers and nonsmokers tend to develop different types of lung cancer.
According to the Washington researchers, most of the tumours found in never-smokers’ lungs are driven by so-called driver mutations in the DNA.
These mutations or errors in the genetic code cause cancerous tumours to grow but can be blocked with the right drugs.
At the same time, only about half of tumours in people who smoke are found to be caused by driver mutations.
Dr Ramaswamy Govindan, the study’s senior author, said: “Most genomic studies of lung cancer have focused on patients with a history of tobacco smoking.
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“And even studies investigating the disease in patients who have never smoked have not looked for specific, actionable mutations in these tumours in a systematic way.
“We found that the vast majority of these patients have genetic alterations that physicians can treat today with drugs already approved for use.
“The patient must have a high-quality biopsy to make sure there is enough genetic material to identify key mutations. But testing these patients is critical.”
According to the expert, there is a high chance these patients will have an “actionable mutation” that can be targeted with specific therapies.
It is estimated between 10 and 15 percent of lung cancers in the US are diagnosed in never-smokers.
And in certain parts of Asia, the figures can be as high as 40 percent.
The Washington researchers analysed lung tumours in 160 patients diagnosed with lung adenocarcinoma – the most common type of lung cancer in the US – who have never smoked.
The data was also compared against The Cancer Genome Atlas and the Clinical Proteomic Tumor Analysis Consortium.
Based on the study, Dr Govindan and his colleagues determined smokers’ lung tumours have about 10 times as many mutations as nonsmokers’ tumours.
He said: “Tobacco smoking leads to characteristic changes in the tumour cells, so we can look for telltale signs of smoking or signs of heavy exposure to secondhand smoke, for example.
“But very few of these patients’ tumours showed those signs, so we could verify that this was truly a sample of lung cancer tumours in patients who had never smoked or had major exposure to tobacco smoke.”
The researchers also found only about seven percent of the studied patients showed these mutations at birth.
Dr Govindan said: “There appears to be something unique about lung cancer in people who have never smoked.
“We didn’t find a major role for inherited mutations, and we don’t see evidence of large numbers of mutations, which would suggest exposure to secondhand smoke.”
About 60 percent of the tumours were found in women and 40 percent in men, even though cancer is more prevalent in men.
According to the expert, some additional genes may be skewing the results, though “we just don’t know what those are yet”.
He added: “The most important finding is that we identified actionable mutations in the vast majority of these patients — between 80 percent and 90 percent.
“Our study highlights the need to obtain high-quality tumour biopsies for clinical genomic testing in these patients, so we can identify the best-targeted therapies for their individual tumours.”
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