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[엠디저널] Lung cancer is the fourth most common cancer following stomach cancer, colorectal cancer and liver cancer. However, the number of lung cancer patients is continuously increasing and the death rate is the highest, taking the first place among the causes of death from malignant tumors not only in Korea but also in the United States and other countries around the world. The 5-year survival rate for lung cancer is very low, regarding 15%. Because there are cases of asymptomatic rather than specific symptoms, only 12% of patients with stage 1 or 2 lung cancer, which can be surgically resected, are due to the fact that lung cancer is more biologically malignant than other cancers. However, if lung cancer is detected in the first stage, the survival rate increases to 70%, so early detection is important.

In the past, 80% of all lung cancers were squamous cell carcinoma related to smoking.

More than 90% of lung cancer is related to smoking, so strong carcinogens in cigarette smoke are an important cause of cancer. Smokers are 10 to 20 times more likely to develop lung cancer than nonsmokers. However, the number of smokers in Korea is not decreasing, and in particular, as the number of adolescents and women who smoke is rapidly increasing, lung cancer is expected to continue to increase in the future. Lung cancer is largely preventable by quitting smoking, so quitting smoking is the best prevention method.

Symptoms and progression of lung cancer

Lung cancer is classified into small cell lung cancer and non-small cell lung cancer according to the tissue shape and cancer cell characteristics. Non-small cell lung cancer, which accounts for 80% of all lung cancers, is classified into adenocarcinoma, squamous cell carcinoma, and large cell carcinoma according to the shape of the cells. Small cell lung cancer is treated with chemotherapy, and non-small cell lung cancer is treated with surgery. On the other hand, there are primary lung cancer, in which cancer occurs in the lung tissue, and metastatic lung cancer, in which cancer originating in an organ other than the lungs moves to the lungs via blood vessels or lymphatic vessels and proliferates.

There are symptoms caused by the primary tumor itself occurring in the lungs, symptoms caused by invading the rib cage in the lungs, symptoms caused by metastasis to organs other than the lungs, and symptoms caused by hormones produced by the tumor. However, 5 to 15% of lung cancer patients have no symptoms.

The first symptom of lung cancer is cough with no specific cause. Blood is sometimes mixed with the sputum, which is also a symptom of the tumor itself occurring in the lung tissue. Acupuncture of the rib cage around the lungs may cause respiratory distress due to tracheal obstruction, difficulty swallowing due to esophageal compression, and hoarseness of the voice.

Lung cancer metastasizes to various organs, but metastases to the brain or bone are common. Metastasis to the brain can cause pain, fractures, and spinal cord compressions. In addition, due to substances such as hormones produced in the tumor, loss of appetite, general weakness, clubs with fingertips changing like clubs, myasthenia gravis, etc. may appear.

The only treatment for curing non-small cell lung cancer, which accounts for 80% of all lung cancers, is radical resection, which is detected early and surgically removed. However, in Korea, the rate of detection in the 1st and 2nd stages where surgery is possible is very low compared to developed countries. In most cases, inoperable local progression is detected in stage III or metastatic stage IV, and most die within one year of diagnosis. In addition, regarding half of patients who underwent radical resection have recurrence.

Small cell lung cancer, which accounts for 15-20% of all lung cancers, has a unique clinical picture unlike other lung cancers. Cancer cells grow rapidly, so the doubling period is 30 days, and it is easy to metastasize at an early stage. Without proper treatment following diagnosis, most of them progress very quickly, leading to death within 3 months, and respond well to chemotherapy or radiation therapy. In other words, small cell lung cancer is considered a systemic disease because it grows quickly and metastasizes well to other organs.

Diagnosis of lung cancer

Lung cancer is divided into central lung cancer and peripheral lung cancer according to the site of occurrence. In central lung cancer, lung cancer occurs mainly in the airways and appears in the form of nodules, and when the bronchial lumen is blocked, pneumonia or atelectasis occurs. Most peripheral lung cancers also appear in the form of nodules, and as the mass grows, enlargement of the hilar lymph nodes may be accompanied. In general, small-cell lung cancer and squamous contraception are central, and adenocarcinoma and large-cell lung cancer are peripheral.

The most basic examination is a chest X-ray. However, there is a limit to early diagnosis because the size of lung cancer must be greater than 10 millimeters to be detected. When lung cancer is detected, cancer has already progressed in many cases, so for rapid and accurate examination, it is recommended to diagnose through a low-dose chest CT scan with a low radiation dose. Chest CT is an essential test for staging because it can determine the size, location, and invasion of surrounding major organs and lymph nodes. In particular, it is performed to check for mediastinal lymph nodes and pleural involvement before surgery. Low-dose chest CT can detect nodules as small as 3 millimeters. Low-dose chest CT can detect nodules as small as 3 millimeters. The radiation dose of normal chest CT is 7mSv, but low-dose chest CT is regarding 1.5mSv, which is only one-fifth of that of normal chest CT. Therefore, once a low-dose chest CT is taken, and if it is necessary to distinguish whether it is cancer or not, biopsy and PET-CT are additionally tested.

The bronchoscopy is similar to the gastroscopy, but it is to insert a thinner tube than the gastroscope into the airway through the nose to observe whether the trachea and the tracheal branch have invaded the middle. The location of the tumor can be confirmed and confirmed by bronchial lavage, tissue, or biopsy. Usually, the test takes regarding 30 minutes, but if you vomit during auditing, food can pass into the airways and cause pneumonia, so you should fast for at least 8 hours before the test. After bronchoscopy, do not consume food or drink, including water, until the local anesthesia in the neck is removed.

treatment of lung cancer

When lung cancer is diagnosed, the stage is determined according to the size of the lung cancer mass, the degree of invasion of surrounding tissues and lymph nodes, and whether it has metastasized to other organs, and whether the tumor can be resected by surgery is evaluated. In the case of lung resection, it should be evaluated whether there is any difficulty in carrying out daily life with the remaining lungs.

Since non-small cell lung cancer progresses gradually, it can be cured with surgery if detected early.

In general, most patients with stage 1 or 2 lung cancer can be operated on, and more than half of those with stage 3 lung cancer can be operated on. However, surgery is possible in regarding 20% of patients with non-small cell lung cancer. Therefore, in the case of stage 3 or higher non-small cell lung cancer for which curative surgery is difficult, chemotherapy and radiation therapy are combined.

When the lung is resected, lobectomy is performed. The right lobe consists of an upper lobe, a middle lobe, and a lower lobe, and the left lobe consists of an upper lobe and a lower lobe. At this time, the adjacent mediastinal lymph nodes are also removed. Various methods such as radiation therapy, chemotherapy, targeted therapy, and immunotherapy are tried depending on the stage.

Treatment for non-small cell lung cancer varies depending on the stage. Stage 1, when the size of the cancer is 3 cm or less, is surgery in principle, and stage 2 is a combination of surgery, radiation therapy, and chemotherapy. Stage 3 surgery is performed following the tumor has invaded the surrounding tissue or lymph node treatment is performed. In the case of stage 3 and 4, which cannot be resected by surgery, combined chemotherapy and radiation therapy are performed, otherwise chemotherapy and treatment to alleviate symptoms are performed.

In Korea, the most common adenocarcinoma can use targeted therapeutics according to individual genetic characteristics, so the target gene whose expression is increased by genetic mutation is identified by examining the tumor tissue. Adenocarcinoma has epithelial growth factor receptor (EGFR) mutations in 30-40% of cases, and it is common in Asian non-smokers. In 5% of adenocarcinoma patients, the ALK gene is overexpressed, a gene that plays a crucial role in tumor development and progression. If no specific gene abnormality is found in the genetic test, or for adenocarcinoma or squamous cell lung cancer, which is difficult to test, cytotoxic chemotherapy is used.

On the other hand, our body has immune cells that attack cancer cells, recognizing and attacking specific proteins on the surface of cancer cells to remove cancer cells. avoid Immunotherapy induces immune cells to attack cancer cells by inhibiting PD-LI in cancer cells. Therefore, it is being used as a second-line treatment for overexpressing PD-LI among non-small cell lung cancer patients who have shown resistance to first-line treatment. Side effects are relatively few compared to cytotoxic anticancer drugs, and the effect lasts for a long time in patients who have shown an effect.

Lung cancer recurrence and metastasis

The most important factor in determining the prognosis of lung cancer is the stage of lung cancer. Among the factors that determine the staging of lung cancer, lymph node metastasis is the most important factor in determining the survival rate rather than the size or degree of invasion of the primary tumor. Lymph node metastases have a poorer prognosis and recurrence is more common than those without lymph node metastases. In particular, in the case of mediastinal lymph node metastasis, surgery alone cannot be cured. In addition, the worse the general condition of the patient, the more severe the weight loss, the worse the prognosis for men. In particular, the prognosis is poor when LDH (lactate dehydrogenase) and NSE increase in small cell lung cancer.

The most common place for metastasis of lung cancer is to the brain, and 70% of brain metastases are lung cancer as the primary lesion. The second most common bone is the liver, and the most common site for bone metastasis is the spine, ribs, and pelvis. Even if diagnosed early, 80-90% of small cell lung cancers cause microscopic metastases throughout the body, so they are treated with chemotherapy without surgery. However, the recurrence rate in the primary lesion reaches 30-80%. In lung cancer, the size of the tumor does not necessarily match the clinical course. Even in the case of early lung cancer with a small mass, micrometastasis often occurs and the prognosis is poor.

Lung cancer is usually presumed to have already recurred when the tumor size is 1 to 2 millimeters or more, that is, at the time of angiogenesis. Even in early patients, regarding half of non-small cell lung cancer recurs within 5 years following radical resection, but most of them recur within 2 years, so the cure rate is very low.