Lung Cancer is a malignant tumor originating from the bronchial epithelium, fine bronchial epithelium, alveolar epithelium and bronchial glands, called bronchopulmonary cancer, or lung cancer for short. It is one of the common malignant tumors, with an incidence of nearly 500,000 people each year in China, and the age-specific incidence and mortality rates of lung cancer for both men and women are the highest among all types of cancers. The treatment effect of lung cancer has not improved significantly in the last decade, and the overall cure rate is about 15%. One of the main reasons is that the biological characteristics of lung cancer are very complex and its malignancy is high, and 80% of lung cancer patients are already in advanced stage when they are diagnosed.
The treatment of lung cancer is a multidisciplinary comprehensive treatment including surgery, radiotherapy, chemotherapy, molecular targeted therapy, bioimmunotherapy and Chinese medicine, and individualized treatment for each patient. Information shows that the incidence of lung cancer in China will show a significant increase in a long period of time. Therefore, the prevention and treatment of lung cancer is urgent.
Causes of lung cancer]
1.Smoking: Smoking is the most important causative factor of lung cancer. The smoke produced by cigarette ignition contains more than 3,000 toxic chemicals, the most important of which are nicotine, carbon monoxide, cyanide, various carcinogens in tobacco tar, radioactive isotopes, and heavy metal elements. Carcinogens produced by tobacco combustion include benzo(a)pyrene, nitrosamines, beta-naphthylamine, cadmium, radioactive polonium, and other carcinogenic substances such as phenolic compounds.
The International Agency for Research on Cancer (IARC) includes smoking as one of the human carcinogenic factors and estimates that 85% to 90% of male lung cancer mortality is caused by smoking, and the risk of lung cancer varies with the number of cigarettes smoked per day, the duration of smoking, and the age at which smoking begins. The duration of smoking has a greater effect than the number of cigarettes smoked per day. Smoking three times the number of cigarettes per day increases the risk of lung cancer by a factor of three, while smoking duration increases the risk of lung cancer by a factor of 100 for those who smoke for three times longer.
Therefore, the younger the age of starting to smoke and the longer the duration of smoking, the higher the risk of lung cancer. For example, smokers who smoke an average of 20 cigarettes per day and have smoked for 20 years have a 20 times higher risk of lung cancer than non-smokers. Those who started smoking when they were younger than 20 years old died of lung cancer 28 times more often than nonsmokers. Lung cancer mortality is about 100 times higher for those who have smoked for 60 years than for those who have smoked for 20 years.
Passive smoking is also an important causative factor for lung cancer. Passive smoking means that nonsmokers inhale smoke exhaled by smokers or from burning cigarettes for more than 15 minutes/day at least one day a week. Homes, public places and workplaces are all places that suffer from passive smoking exposure. Studies have found that the risk of lung cancer is higher among non-smoking women whose husbands are smokers than among those whose husbands are non-smokers. The risk of lung cancer among non-smoking women with smokers husbands was 24% higher than that of non-smokers. Two to three percent of newly diagnosed lung cancer cases are related to passive smoking each year.
2. Occupational lung cancer-causing factors: asbestos, arsenic compounds, uranium, chromium compounds, nickel compounds, dichloromethane, ionizing radiation, mustard gas, and polycyclic aromatic hydrocarbons in soot, tar and oil are all risk factors for lung cancer. For example, asbestos workers die from lung cancer 7 times more than the general population, and the risk of lung cancer among asbestos workers who smoke is 50-90 times higher than the general population, which is due to the synergistic effect of smoking and asbestos.
3. Air pollution: including outdoor air pollution and indoor air pollution, industrial emissions, the use of large amounts of coal, diesel and gasoline motor vehicles burned in cities every day can lead to air pollution in dense residential areas. In general, more than 10% of lung cancer incidence in cities is caused by air pollution. Oil smoke and soot pollution in the kitchen is one of the causes of lung cancer in non-smoking women. In recent years, formaldehyde and radon gas released from stone, paint, flooring glue, plastic ornaments and adhesives used in interior decoration have brought indoor pollution, which is also a risk factor for lung cancer.
4. Oncogenes and oncogenes: mutations of multiple genes cause multi-stage cell damage and repair errors, and finally cause cancer. Oncogenes such as Ras, myc, Rb and oncogene p53 are known to be related to the occurrence of lung cancer. For example, the Ras gene is associated with lung squamous carcinogenesis in smokers, while the EGFR gene is associated with lung adenocarcinoma in nonsmokers.
Pathology of lung cancer
(1) Gross typing: According to the site of tumor occurrence, the pathological gross typing of lung cancer can be divided into
1. Central type: Tumors occurring in the bronchus above the segmental and segmental bronchial openings;
2. Peripheral type: tumors occurring in small bronchi, fine bronchi and alveoli below the segmental bronchi.
(2) Histological typing: WHO classifies the histology of lung cancer into
1.Adenocarcinoma: about 35-40%, including subtypes such as alveolar adenocarcinoma, papillary adenocarcinoma, mucinous adenocarcinoma, and fine bronchioloalveolar carcinoma.
2.Squamous cell carcinoma: Squamous carcinoma for short, accounting for 30-35%.
3.Small cell carcinoma: about 15-25%, this type of lung cancer is characterized by high malignancy and prone to metastasis.
4.Large cell carcinoma: accounting for about 10%.
5.Other types of lung cancer include: adenosquamous carcinoma, carcinoid tumor, carcinosarcoma, etc. According to the biological characteristics of lung cancer and different treatment methods, lung cancer is clinically divided into two major categories.
1.Small cell lung cancer: it accounts for about 15-25% of all lung cancers, characterized by high malignancy and easy metastasis, and treated with chemotherapy-based comprehensive therapy.
(2) Non-small cell lung cancer: all types of lung cancer except small cell lung cancer, which accounts for about 75-85% of all lung cancers, and treatment is mostly based on surgery.
(3) Diffusion and metastasis of lung cancer.
1.Direct infiltration: tumor directly invades surrounding organs and tissues, such as mediastinum, chest wall, etc.
2.Lymphatic metastasis: it is the main way of lung cancer metastasis. Early lymphatic metastasis is an important reason for the failure of lung cancer treatment.
3.Bloodway metastasis: lung cancer can cause metastasis to distant organs after entering blood circulation, and the common metastatic sites are: brain, bone, liver, adrenal gland, etc.
4.Bronchial dissemination: It is a characteristic of fine bronchoalveolar carcinoma.
Clinical manifestations of lung cancer]
The high incidence age of lung cancer is 45-65 years old, and the ratio of men to women is 4:1. Clinical manifestations vary depending on the location, size, type of primary tumor, whether it invades surrounding organs and whether it is distantly metastasized. The common manifestations are.
I. Symptoms caused by primary tumor Central type lung cancer shows early and obvious respiratory symptoms, and its common symptoms include: cough, coughing up bloody sputum, shortness of breath, chest pain and fever. Peripheral type lung cancer has no obvious symptoms in early stage, and some of them may show cough.
Symptoms caused by tumor invasion and metastasis Tumor invasion of chest wall causes persistent chest pain; direct invasion of tumor or compression of superior vena cava by right upper mediastinal lymph nodes causes superior vena cava compression syndrome, which is manifested as swelling of head and neck, anger of veins in neck and upper chest; involvement of laryngeal nerve causes hoarseness; compression of esophagus causes difficulty in swallowing; pleural dissemination causes pleural effusion or pericardial effusion; brain metastasis causes headache, vomiting, hemiparesis; bone metastasis causes corresponding symptoms. Bone metastasis causes pain or pathological fracture in the corresponding area; liver metastasis causes anorexia, pain in the liver area, yellowing of body and eyes, ascites, etc.
The concomitant symptoms of lung cancer include: pulmonary hypertrophic osteoarthropathy, manifested as joint swelling and pain, rod-shaped fingers (toes); dermatomyositis; carcinoid syndrome, manifested as abdominal pain and diarrhea, facial flushing, diarrhea, abdominal pain, asthma-like dyspnea; male breast development, etc.
Diagnosis of lung cancer]
The diagnosis of lung cancer must be based on clinical manifestations and various imaging findings, and the final diagnosis must be confirmed by obtaining evidence of cytological or histological pathological diagnosis. The diagnosis of lung cancer includes localization diagnosis and qualitative diagnosis, and all imaging diagnosis methods are classified as localization diagnosis of lung cancer, while all methods of obtaining pathological diagnosis are classified as qualitative diagnosis of lung cancer.
I. Localization diagnosis methods of lung cancer include
1.X-ray examination: it is still an important basic method to detect and diagnose lung cancer, and usually frontal and lateral chest photographs are performed.
2.Computerized X-ray tomography (CT): It has become a routine method to estimate the degree and scope of intrathoracic invasion of lung cancer, especially in clinical staging of lung cancer, and it can detect lung lesions smaller than 1 cm and those located in overlapping areas that are difficult to be detected by chest X-ray, and it is easier to judge the relationship between lung cancer and surrounding tissues and organs. CT of other sites such as brain, liver and adrenal glands can exclude distant metastases from lung cancer related sites. The low-dose spiral CT scan in recent years has improved the screening and diagnosis of lung cancer without increasing the lung cancer induced rate of radiation.
3.Magnetic resonance imaging (MRI): It can better clarify the relationship between tumor and large blood vessels, or suprapulmonary sulcus tumor to understand the involvement of chest wall and brachial plexus nerve. However, it is not as sensitive as CT in finding small lesions.
4.Positron emission tomography (PET and PET/CT): a metabolic imaging technique developed in recent years, using the different metabolism of FDG between normal cells and lung cancer cells, combined with CT, it can combine the qualitative advantages of metabolism and the localization characteristics of morphology to make the diagnosis more accurate. However, it is expensive and cannot be widely used.
5.Single photon emission computed tomography (SPECT): It uses the difference between the amount of radionuclide uptake by tumor cells and normal tissues for tumor localization, qualitative diagnosis and diagnosis of bone metastasis of lung cancer. Usually, bone metastases can be detected 3-6 months earlier than ordinary X-rays.
6.Abdominal ultrasound: to understand whether there are metastases in the liver and adrenal gland.
II. Qualitative diagnosis of lung cancer includes
1.Sputum exfoliative cytology examination: it is one of the important methods to diagnose lung cancer, which is simple, convenient and non-invasive. The sputum with blood is better than the morning sputum coughed up from deep in the lungs. The positive rate of blood sputum is higher, and the detection rate can be improved by 3 consecutive days. Positive cytologic results can be obtained before the lesion is detected by imaging.
2.Fiber bronchoscopy: It is the most important means in lung cancer diagnosis. It can directly observe the lesions in the trachea and bronchi, and can be clamped and wiped under direct vision to obtain pathological histological and cytological diagnosis. Cytology can be performed using bronchial irrigation fluid for peripherally located lesions. Biopsy of bronchial endothelial staining using blood serum derivatives in combination with laser or methylene blue can increase the rate of positive early diagnosis. Even mediastinal or pulmonary puncture can be performed via fibrinoscopy, and ultrasound technology can be used to understand the tumor condition, relationship with surrounding organs and lymph nodes, so as to guide the design of surgical treatment plan.
3.Transthoracic wall fine-needle aspiration biopsy: guided by X-ray, ultrasound or CT, more reliable than bronchial fibrinoscopy, may have complications such as pneumothorax.
4.Other cytological or pathological examination: for example, patients with lung cancer with pleural fluid can be examined by pleural fluid aspiration, pleural, lymph node, liver and bone marrow biopsy, etc.
5.Mediastinoscopy: mediastinoscopy is a diagnostic method to observe the peri-tracheal lesions through the artificial tunnel in the anterior space of trachea, and it is also a diagnostic method to biopsy. It plays an important role in determining whether there is mediastinal lymph node metastasis of lung cancer, and is an important means of lung cancer staging, and can also be used for differential diagnosis of difficult diseases in the chest.
6.Thoracoscopy: TV-assisted thoracoscopic surgery (TATS) is one of the rapidly developing minimally invasive surgical techniques in recent years, which plays an increasing role in lung cancer diagnosis, differential diagnosis, staging and treatment. It is mainly suitable for pleural lesions, malignant pleural fluid and diffuse diseases of the lung. In recent years, VATS is increasingly used for the surgical treatment of early lung cancer, which does not affect the overall survival rate compared with conventional open-chest surgery, and thus takes into account the postoperative shape and functional recovery of patients.
7.Open-chest biopsy: For patients whose diagnosis cannot be confirmed by sputum cytology, bronchial fibrinoscopy and needle biopsy, open-chest biopsy can be considered according to the balance of advantages and disadvantages such as slow age and lung function.
In addition, tumor markers can reflect the existence of tumor, detect the effect of tumor treatment, and serve as a class of substances for tumor treatment targets. Such as CEA, SCC, NSE, Cyfra21-1, etc., have certain roles in lung cancer screening and efficacy evaluation.
【Treatment of lung cancer】.
Treatment of lung cancer should be based on comprehensive analysis of patient’s general condition, pathological type and clinical stage, and multidisciplinary comprehensive treatment. Its main methods are.
(1) Surgical treatment: For early stage non-small cell lung cancer, if there is no contraindication to surgery, surgery should be preferred. Lobectomy plus mediastinal lymph node dissection in the lung hilum is the preferred procedure.
(2) Radiation therapy: For early-stage lung cancer that cannot undergo surgery due to various reasons, radical radiation therapy should be chosen. Radiation therapy should also be used for preoperative and postoperative comprehensive treatment. Local palliative radiotherapy can relieve pain and inhibit tumor growth.
(3) Chemotherapy: small cell lung cancer and advanced non-small cell lung cancer shall be treated with chemotherapy; it is also applied to the comprehensive treatment before and after surgery or before and after radiotherapy.
(4) Molecular targeted therapy: It has become the new direction of malignant tumor treatment in the 21st century and has achieved certain achievements, such as EGFR-TK inhibitor “Gefitinib” has special effect on female non-smoking lung adenocarcinoma.
(5) Local radiofrequency ablation, biological therapy, immunotherapy and gene therapy for lung cancer are all being explored. Chinese herbal medicine is mainly used for adjuvant treatment.
The prognosis of lung cancer is still poor. For radical resection, its 5-year survival rate is about 40%, while for patients in the middle and late stages who are not suitable for surgical resection, chemotherapy or radiation therapy is used, which is less effective than surgical resection, therefore, lung cancer is still one of the tumors with high mortality rate. Lung cancer treatment not only requires multidisciplinary comprehensive treatment, but also advocates “individualized treatment” in recent years. It has become the key to improve the efficacy of lung cancer treatment.
Prevention of lung cancer
I. Primary prevention of lung cancer
Smoking is the main cause of lung cancer, and controlling smoking is the key to preventing or reducing the occurrence of lung cancer. A study of American veterans found that the risk of lung cancer after smoking cessation was significantly lower than that of non-smokers, and the longer the cessation time, the smaller the risk. In Europe and the United States, smoking control has brought about significant results in public health. In the United Kingdom, smoking rates have declined steadily over the past 30 years since the launch of the smoking control campaign, and mortality from lung cancer in men began to decline after reaching a plateau in 1975-1979.
As a result of public health education and government measures, the smoking rate in the United States declined from 55% in the mid-twentieth century to 28% in the 1990s, and the incidence of lung cancer in men has declined at a rate of 1.4% per year since its peak in 1984 (86.5 per 100,000); the mortality rate has declined at a rate of 1.6% per year since its peak in 1990 (75.2 per 100,000). According to the World Health Organization, eliminating smoking is effective in reducing the incidence of lung cancer, and more effort and funding should be devoted to primary prevention of lung cancer. By controlling smoking, encouraging people not to smoke or quit smoking as early as possible, reducing the smoking rate of the population, and eliminating the main causes of lung cancer, will certainly effectively reduce the incidence and mortality rate of lung cancer.
2.Improve the environment, improve the indoor and outdoor air quality is another important means to prevent lung cancer.
3.To carry out labor hygiene and strengthen occupational protection to prevent occupational lung cancer.
4.Diet prevention, advocate healthy diet and consume more green vegetables.
Secondary prevention of lung cancer
The primary screening and early diagnosis of lung cancer mainly apply X-ray, frontal and lateral chest films, CT, sputum exfoliation cytology, fiber bronchoscopy and tumor markers. In turn, early detection, early diagnosis and early treatment can be achieved.
Tertiary prevention of lung cancer
Although there has been great progress in the clinical treatment of lung cancer in recent years, most of the patients are diagnosed in the middle and late stages after the emergence of typical symptoms for a period of time, so they have lost the opportunity of early diagnosis and treatment, as well as the characteristics of lung cancer itself. Tertiary prevention is to prevent recurrence and metastasis, focus on rehabilitation, palliative and pain relief treatment, and provide physiological, psychological, nutritional and exercise guidance to maximize the survival rate and quality of life of patients.