Reprinted from the Lung Cancer Patient Education Handbook
Lung cancer is the abbreviation of primary bronchial lung cancer. Cancer cells originate from the bronchial mucosa or glands. In China, lung cancer is the most common malignant tumor in men, and the second most common malignant tumor in women after breast cancer. Currently, the incidence and mortality rate of lung cancer in China is still growing rapidly, and the number of incidence has increased nearly five times in the past 30 years, and it has become the first cause of death in urban population, with about 600,000 people dying of lung cancer in China every year. Lung cancer mostly develops at the age of 40 or above, and its peak incidence age is between 60 and 79. The ratio of male to female prevalence is about 2.3 to 1. Zhiyong Ma, Department of Internal Medicine, Henan Cancer Hospital
At present, it is believed that lung cancer is the result of many factors, especially related to poor life style. Long-term heavy jong smoking is the most dangerous factor for lung cancer, and 90% of lung cancer patients have a history of active smoking or passive smoking. Compared to nonsmokers, jong smokers have a 20-fold increased risk of dying from lung cancer. The occurrence of lung cancer in smokers is related to the number of years they have been smoking, the number of cigarettes they smoke per day, the age they started smoking, and the type of cigarettes they smoke. People with a smoking index (number of cigarettes smoked per day x number of years of smoking) > 400 are at high risk for lung cancer. The most effective way to prevent lung cancer is not to smoke and to quit smoking as early as possible. Therefore, for the health of yourself and others, you should quit smoking early. Other risk factors for lung cancer include atmospheric pollution, environmental carcinogenic factors, immune status of human body, genetic factors and so on.
Only on the basis of clear diagnosis and thorough examination can we accurately classify cancer types and disease stages and formulate the most appropriate treatment plan. Like other malignant tumors, the definite diagnosis of lung cancer relies on pathological examination. The commonly used pathological examination methods in clinical practice include sputum exfoliative cytology, fiberoptic bronchoscopy biopsy, percutaneous lung tissue aspiration biopsy, mediastinoscopic biopsy and resection biopsy of superficial metastatic lesions. After lung cancer is clearly diagnosed by pathology, CT, magnetic resonance imaging (MRI), bone imaging, blood test, ultrasonography, positron emission tomography (PET)-CT and other tests can be performed, which are all clinically useful for the diagnosis and staging of lung cancer.
At present, surgery, radiotherapy, chemotherapy, molecular targeted therapy and interventional therapy are the main treatment methods for lung cancer. Each of these therapies has its own advantages and is effective for lung cancer patients, and can be used individually or in combination. However, the selection of specific treatment options is influenced by the patient’s physical condition, the pathological type, invasion scope and development trend of the tumor. The treatment of lung cancer emphasizes the “triple combination”, i.e., integrated, individualized and standardized, which is the key to improve the long-term survival rate of lung cancer patients. In addition, early detection, early diagnosis and early treatment of lung cancer are very crucial. For example, the 5-year survival rate of early lung cancer patients can reach about 70% after standardized and comprehensive treatment, mainly surgery.
What does our lung look like?
The lungs have a soft, spongy structure that can be stretched during breathing. The left and right lungs are located on each side of the chest cavity. The lungs are divided into several parts by deep grooves called fissures, each with one lobe. The left lung is divided into two lobes, the lobe and the lower lobe, by a horizontal fissure. The right lung is divided by two fissures into three lobes, the upper, middle and lower lobes. The right lung is slightly larger than the left lung.
The two lungs are separated by the mediastinum in the center of the chest, and the central depression of the lung near the mediastinum is called the hilum, which is the site where the blood vessels, main bronchi and nerves of the lung enter and exit the lung. The trachea is divided into the left and right main bronchus, the first level bronchus, and the main bronchus enters the pulmonary hilum and then further branches out into the second and third level bronchus, which branches out again and again until the thinnest. The branches of the bronchi resemble branches and are called bronchial trees. The numerous pouch-like structures at the end of the bronchial tree are called alveoli.
The lungs are the respiratory organs of the body. When inhaling, the lungs supply the body with essential oxygen; when exhaling, the lungs continuously expel the carbon dioxide produced by the body. This process is carried out through gas exchange between the alveoli and the blood in the pulmonary capillaries.
What are the types of lung cancer? What are the characteristics of each type?
Lung cancer can be divided into the following types according to its location on the bronchi.
1. Central type lung cancer
The tumor is located in the central part of the lung and occurs above the third level bronchus, accounting for about 3/4 of lung cancer, mostly seen in squamous carcinoma and small cell lung cancer (SCLC).
2. Peripheral type lung cancer
The tumor is located in the periphery of the lung and occurs below the third level bronchus, accounting for about 1/4 of lung cancers, mostly adenocarcinoma.
3. Diffuse lung cancer
Tumors are diffusely distributed in the lung and occur in the fine bronchi and alveoli.
According to the degree of differentiation and morphological features of lung cancer under microscope, it can be divided into the following two types (Figure 4).
1. Non-small cell lung cancer
Non-small cell lung cancer (NSCLC) accounts for about 4/5 of lung cancers, and its growth and spread are relatively slow, which can be subdivided into the following types.
Adenocarcinoma: accounts for 35% to 40% of lung cancer. Adenocarcinoma can be either peripheral lung cancer or central lung cancer, with the former being slightly more common. Adenocarcinoma is most common in women, nonsmokers and former smokers. Adenocarcinoma is rich in blood vessels, so local infiltration and hematogenous metastasis are early, and it is easy to metastasize to liver, brain and bone, and also to the pleura and cause pleural effusion.
Squamous cell carcinoma: referred to as squamous carcinoma, accounting for 30%-35% of lung cancer, mainly central type lung cancer, but peripheral type is rare. It is mostly seen in elderly men and is very closely related to smoking. Squamous carcinoma has slow growth, late metastasis, more opportunities for surgical resection, and higher 5-year survival rate of patients.
③Large cell carcinoma: accounts for 10%-15% of lung cancer. Large cell carcinoma metastasizes later than SCLC and has a better chance of surgical resection.
④Other: adenosquamous carcinoma, sarcomatoid carcinoma, carcinoid carcinoma, salivary gland carcinoma, etc.
2. Small cell lung cancer
Small cell lung cancer (SCLC) accounts for about 1/5 of lung cancer, and patients are mostly aged 40-50 years old and have a history of smoking. Its malignancy is very high, the cancer cells grow fast, infiltrate strongly, and metastases easily, and the patients’ expected survival is poor. About 70% of SCLC patients have distant metastasis at the time of initial diagnosis. SCLC can be broadly classified into oat cell type, intermediate type and mixed type.
How to choose the appropriate treatment according to the type of lung cancer?
The purpose of lung cancer staging is to distinguish the differences in biological behavior, clinical characteristics, pathological features and expected survival of different types of tumors so as to select the corresponding treatment, especially the pathological staging of lung cancer is closely related to its treatment.
Surgery, radiotherapy, chemotherapy and targeted therapy are the main tools for the treatment of NSCLC. The emerging targeted therapy has better efficacy in specific populations and has become an indispensable part of the comprehensive treatment of NSCLC. Surgical procedures are mainly applied to early stage NSCLC, but because of the early symptoms of lung cancer are not obvious, 70% to 80% of patients are already in the middle to late stage when they are diagnosed, resulting in the survival of NSCLC patients is still poor. In fact, with the increase of early diagnosis and treatment of lung cancer and the progress of medicine, the survival time of NSCLC patients has been extended. In the future, advanced lung cancer is expected to become a chronic disease, and lung cancer patients can effectively control their disease and “survive with tumor” for a long time through scientific medicine under the guidance of doctors, just like diabetic patients. Therefore, lung cancer patients should abandon the incorrect view that “cancer is a terminal disease”.
SCLC is a malignant tumor that is sensitive to chemotherapy and radiotherapy, and has a high efficiency in recent treatment, but often has a short remission period. Chemotherapy is the cornerstone of SCLC treatment, and surgery is of very limited value in the comprehensive treatment of SCLC patients. Nevertheless, with the continuous development of medical science in recent years, the treatment outcome of SCLC is gradually improving. Rational use of chemotherapy and radiotherapy-based combination therapy can prolong the survival of patients and improve the quality of life. In addition, prophylactic whole brain irradiation can effectively reduce the incidence of intracranial metastases in SCLC patients.