Lung cancer is the malignant tumor with the highest incidence and mortality rate in China. While benign lung diseases such as pneumonia, emphysema, and asthma are all common in clinical practice, you may be concerned about whether they can develop into lung cancer. Is this concern justified? Let’s talk about this issue.
I. Some lung diseases can increase the risk of lung cancer
1. Chronic bronchitis
A pooled analysis included 24,607 lung cancer cases and 81,829 control patients from 17 studies by the International Lung Cancer Consortium to elucidate the role of previous lung disease in lung cancer development.
The results showed that patients with a history of chronic bronchitis had a 1.47 times greater risk of lung cancer than those without such a history, after excluding the effects of age, sex, and smoking.
2. Emphysema
In the above pooled analysis, after excluding the effects of age, sex, and smoking, the risk of lung cancer was 2.44 times greater in patients with a history of emphysema than in those without such a history.
3. Chronic obstructive pulmonary disease (COPD)
Chronic bronchitis and emphysema are both chronic obstructive diseases of the lungs, usually with symptoms of “breathlessness” and coughing and phlegm. (Patients with these two diseases are also diagnosed with “slow-onset lung” if they are found to have persistent airflow limitation on pulmonary function tests.) During the test, the maximum amount of breath that can be taken after the maximum possible inspiration and the maximum possible exhalation is called the “forceful lung volume” (FVC), and the volume of breath exhaled in the first second during exhalation is called the “forceful expiratory volume in one second” (FEV1). When examined, an FEV1/FVC < 70% after inhalation of a bronchodilator is diagnostic of persistent airflow limitation.
And impaired lung function also increases the risk of lung cancer. A community-based cohort study examined the relationship between lung function and lung cancer risk in 6,317 Japanese-American men. Approximately 22 years of follow-up identified 172 individuals who developed lung cancer. Subjects were divided into four groups according to average decreasing lung function from good to poor, and after removing the effects of age and smoking, the risk of lung cancer was 2.1 times higher in the group with the worst lung function than in the group with the best lung function. Another study also showed that the poorer the lung function, the higher the risk of lung cancer.
4. Pneumonia
In the pooled analysis above, after excluding the effects of age, sex, and smoking, the risk of lung cancer was 1.57 times higher in patients with a history of pneumonia than in those without such a history.
5. Tuberculosis
In the above pooled analysis, after excluding the effects of age, sex, and smoking, the risk of lung cancer was 1.48 times greater in patients with a history of tuberculosis than in those without such a history.
This pooled analysis also found that this increased risk of lung cancer encompassed all histologic types of lung cancer (adenocarcinoma, squamous cell carcinoma, and small cell lung cancer) and that among never smokers, former smokers, and current smokers, the risk of lung cancer was increased in patients with a history of these lung diseases.
6. Idiopathic pulmonary fibrosis
This is a disease in which the interstitial lung becomes fibrotic and can lead to thickening of the lung tissue and loss of oxygen exchange, which can be life-threatening in severe cases.
One study examined the association between this disease and the risk of lung cancer in 890 patients with this disease and 5,884 control subjects. The results found that the incidence of lung cancer was 7.3 times higher in people with idiopathic pulmonary fibrosis than in the general population; 8.25 times higher after removing the effect of smoking; and 7.36 times higher for current smokers.
That is, the risk of lung cancer in people with idiopathic pulmonary fibrosis is more than 7 times that of the general population, regardless of whether the effects of smoking are taken into account.
7. Asthma
A meta-analysis in the United States showed that among nonsmokers, the risk of lung cancer in people with asthma was 1.8 times greater than in people without asthma. Among people who smoked, after removing the effect of smoking itself on lung cancer risk, people with asthma were still 1.7 times more likely to develop lung cancer than non-asthmatic people; when the effect of smoking was taken into account, people with asthma were 1.4 times more likely to develop lung cancer than non-asthmatic people.
8. Pneumoconiosis
A prospective cohort study in the Netherlands included 58,279 men aged 55 to 69 years with specific occupational exposures such as asbestos, and after 4.3 years of follow-up, 524 cases of lung cancer were identified. After excluding the effects of age, smoking, and diet, patients with asbestosis had 3.5 times the risk of developing lung cancer compared with the general population.
II. Why?
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1. Some diseases have common causes with lung cancer
For example, smoking increases both the incidence of benign lung diseases such as emphysema and chronic bronchitis, and the incidence of lung cancer. Inhalation of dust such as asbestos, which causes pneumoconiosis, can also lead to lung cancer.
2. Factors such as chronic inflammation of the lungs from certain diseases may promote lung cancer
The data on the association between each lung disease and lung cancer above show that these lung diseases are still independently associated with an increased risk of lung cancer after the effect of smoking has been excluded using statistical methods, suggesting that these diseases are themselves independent risk factors for lung cancer.
All of these diseases have chronic inflammation, some reduce clearance of harmful substances from the lungs, some have increased oxygen free radicals, and some have scarring; diseases such as asthma require glucocorticoid therapy, which may reduce immunity, all of which may increase cancer risk.
In conclusion, some benign lung diseases may increase the risk of lung cancer and should not be taken lightly. On the one hand, smoking and dust inhalation should be avoided and proper exercise should be done to reduce the occurrence of these diseases; on the other hand, the disease should be treated aggressively to reduce chronic inflammation.
Co-reviewed by: Guangdong Provincial People’s Hospital Guangdong Institute of Lung Cancer Liao Riqiang, deputy chief physician Dong Song, MD Zhang Chao, MD