Smokers diagnosed with chronic obstructive pulmonary disorder (COPD) have an increased risk of developing small-cell lung cancer (SCLC) almost twice as much as smokers with no COPD. This is the finding of a large epidemiological study for the lung cancer.
COPD is a progressive lung disease characterized by breathing difficulties as the air sac walls get damaged, the airways become inflamed or thick, and the lungs produce an abnormal amount of mucus. Although COPD can develop due to long-term exposure to irritants such as air pollution, it is more commonly caused by smoking. It doesn't have a cure and is one of the leading causes of disabilities in the United States.
SCLC, on the other hand, makes up at least 10% of all the lung cancer cases, according to the American Cancer Society. It is characterized by the quick spread of cancer cells, which normally begin in the bronchi close to the central part of the chest. Because of its quick progression, patients are often diagnosed in the late stage of the disease. The outlook is poor with the survival rate pegged at around 2% for those who are already in stage IV.
A team of researchers from the Harvard T.H. Chan School of Public Health led by Christiani, a professor in environmental genetics, already know the common association between COPD and SCLC, but their work seeks to be more precise of the link.
The team analyzed the health data such as the smoking habits and lung cancer history of more than 4,000 people with SCLC and over 35,000 without SCLC from around 22 studies in the Internal Lung Cancer Consortium.
Smokers with COPD have at least 1.86 chance of developing SCLC than smokers who didn't have COPD. Further, COPD constitutes 8% of the SCLC cases among the smokers group. Chain smoking still accounts for the biggest possibility of SCLC. Those who consumed a pack a day within the next 20 years have more than four times the risk than non-smokers. The risk can be as high as 70 times if a person would smoke for around 80 years.
The study is now available in EBioMedicine.