Pulmonary diseases and lung cancer are the leading causes of morbidity and mortality worldwide.

According to the World Health Organization, lung cancer accounted for 1.76 million deaths in 2018, and chronic obstructive pulmonary disease (COPD) affected more than 251 million people worldwide in 2016. Several studies have investigated the correlation between pulmonary diseases and lung cancer, and this article aims to provide a comprehensive review of the current state of knowledge on this topic.

Chronic Obstructive Pulmonary Disease (COPD) and Lung Cancer

COPD is a chronic lung disease characterized by chronic bronchitis (inflammation and narrowing of the airways) and emphysema (destruction of lung tissue).

COPD is primarily caused by smoking, but other risk factors include air pollution, occupational exposure to dust and chemicals, and genetic predisposition. Several studies have reported a higher incidence of lung cancer in patients with COPD compared to the general population.

A meta-analysis of 16 cohort studies found that COPD was associated with a 2-fold increase in lung cancer risk, independent of smoking status. The risk appears to be greater in patients with severe COPD or emphysema, and those who continue to smoke despite the diagnosis of COPD.

Asthma and Lung Cancer

Asthma is a chronic lung disease characterized by inflammation and narrowing of the airways. Asthma is often triggered by allergens or irritants such as pollen, dust, or air pollution.

The relationship between asthma and lung cancer is complex, and some studies have reported conflicting results. A large cohort study conducted in Sweden found no overall association between asthma and lung cancer risk, but a higher risk was observed in patients with severe asthma or those who had been hospitalized for asthma in the past.

Another study of more than 2 million individuals in the United Kingdom found that asthma was associated with a slightly increased risk of lung cancer, particularly in women.

Tuberculosis and Lung Cancer

Tuberculosis (TB) is a bacterial infection that primarily affects the lungs. TB is an important risk factor for lung cancer, especially in areas with a high incidence of TB such as Asia, Africa, and parts of Europe.

TB and lung cancer share several risk factors, including smoking and exposure to indoor and outdoor air pollution. TB also causes chronic inflammation in the lungs, which may promote the development of lung cancer.

A meta-analysis of 48 studies reported a 2-fold increase in lung cancer risk among TB patients, with a stronger association observed in men and in patients with a history of smoking.

Interstitial Lung Disease (ILD) and Lung Cancer

ILD is a group of lung disorders characterized by inflammation and scarring of the lung tissue.

ILD can be idiopathic (of unknown cause) or secondary to other conditions such as connective tissue diseases, occupational exposure to dust and chemicals, or drug toxicity. Several studies have reported an increased risk of lung cancer in patients with ILD, particularly idiopathic pulmonary fibrosis (IPF).

The underlying mechanisms linking ILD and lung cancer are not fully understood, but chronic inflammation and tissue damage in the lungs may contribute to the development of cancer. A meta-analysis of 11 studies reported a 2-fold increase in lung cancer risk in patients with IPF, and a higher risk was observed in patients with a longer duration of ILD or a history of smoking.

Pneumonia and Lung Cancer

Pneumonia is an infection of the lungs that can be caused by bacteria, viruses, or fungi. Pneumonia is a common lung disease, especially in older adults and those with weakened immune systems.

Several studies have investigated the relationship between pneumonia and lung cancer, but the evidence is conflicting. Some studies have reported an increased risk of lung cancer in patients with a history of pneumonia, while others have found no association or even a reduced risk.

The underlying mechanisms linking pneumonia and lung cancer are not clear, but chronic inflammation and impaired immune function may play a role.

Cystic Fibrosis and Lung Cancer

Cystic fibrosis (CF) is a genetic disorder that affects the lungs and other organs. CF is characterized by thick, sticky mucus that clogs the airways and makes it difficult to breathe.

CF patients are at increased risk of lung infections, chronic inflammation, and lung damage. Several studies have reported an increased risk of lung cancer in CF patients, although the risk is still relatively low compared to other risk factors such as smoking.

The underlying mechanisms linking CF and lung cancer are not fully understood, but chronic inflammation and tissue damage may contribute to the development of cancer.

Lung Cancer Screening in Patients with Pulmonary Diseases

Lung cancer screening with low-dose computed tomography (LDCT) has been shown to reduce mortality in high-risk individuals, including current and former smokers.

However, the optimal screening strategy for patients with pulmonary diseases such as COPD, ILD, or asthma is not well established. Pulmonary diseases may affect the accuracy and interpretation of LDCT scans, and some studies have reported a higher rate of false-positive results and unnecessary follow-up tests in patients with pulmonary diseases.

Further research is needed to develop effective screening strategies for this population.

Conclusion

The correlation between historical pulmonary diseases and lung cancer risk is complex and multifactorial.

Smoking is the most important risk factor for both pulmonary diseases and lung cancer, but other factors such as exposure to air pollution, genetic predisposition, and chronic inflammation may also play a role. Patients with pulmonary diseases, especially COPD, ILD, and CF, are at increased risk of lung cancer and may benefit from close monitoring and early detection through lung cancer screening.

Further research is needed to develop effective screening strategies and to understand the underlying mechanisms linking pulmonary diseases and lung cancer.