Chronic obstructive pulmonary disease (COPD) appears to be a risk factor for lung cancer, liver cancer, and colorectal cancer, regardless of smoking status, a data study from Korea reported.
The study, “Cancer development in patients with COPD: a retrospective analysis of the National Health Insurance Service-National Sample Cohort in Korea,” was published in the journal BMC Pulmonary Medicine.
COPD is a known risk factor for lung cancer, but its relationship to other cancers has not been reported.
Many of the mechanisms proposed to explain how lung cancer develops in COPD patients, however, are not limited to the lungs. These include cellular damage caused by chronic inflammation, oxidant-induced DNA damage, and the shortening of telomeres — DNA–protein structures found at both ends of each chromosome.
To test their hypothesis, they looked for associations between cancer, COPD, and other environmental factors in 514,795 individuals registered at the National Health Insurance Service–National Sample Cohort (NHIS-NSC). This service, South Korea’s single-payer health insurance system, covers the country’s entire population (about 48 million people as of 2003).
After excluding patients with prior histories of cancer, a group of 321,342 never-smokers, 42,444 former smokers, and 115,304 smokers were identifed. These groups were further subdivided into those with or without COPD.
Data showed that over a 12-year period — from Jan. 1, 2004, to Dec. 31, 2015 — lung cancer occurred more often among smokers (14.87%), former smokers (11.89%), and never smokers (7.82%) with COPD, than among never smokers without COPD (2.44%).
Cancers of the stomach, liver, esophagus, bladder, kidneys, and colorectal cancer were also more frequent in the presence of both smoking and COPD.
COPD associated strongly with lung cancer, regardless of smoking status, supporting evidence that it does indeed play a role in lung cancer development. Furthermore, COPD associated with liver and colorectal cancer, also regardless of smoking status, suggesting that the disease in some way contributes to the development of these cancers.
In keeping with the complex nature of cancer, the study showed that environmental factors contributed to the risk of developing lung cancer. In particular, older age, male sex, a lower body mass index (BMI), and exercise level — together with a COPD diagnosis and smoking history — were identified as independent risk factors.
Older age and male sex were also found to be risk factors for COPD, overlapping with those for lung cancer. Other risk factors for COPD included low income, pulmonary tuberculosis, and asthma.
Although more studies are needed to confirm these findings in larger groups, “data demonstrated that a COPD diagnosis was an independent risk factor contributing to the development of lung cancer and, colorectal cancer and liver cancer among other major cancers, irrespective of smoking status in the Korean population,” the researchers concluded.
Because of the diverse set of risk factors identified in the study, the team suggested that “multidisciplinary approaches are required for the prevention of lung cancer in COPD patients.”
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