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Lung cancer is a disease characterized by abnormal growths, or cancers, in the lungs. Most of the lung tumours are malignant, i.e. they spread throughout the body by destroying the healthy tissues around them. Because of this, lung cancer is a very life-threatening type of cancer and one of the most difficult cancers to treat.
Brief Outlook of Lung Cancer
SIGNS AND SYMPTOMS OF LUNG CANCER
People with lung cancer do not exhibit any symptoms when the cancer is diagnosed and until it has spread. Some of the most common symptoms of lung cancer are:
- Persistent cough which worsens over time
- Haemoptysis, i.e., coughing up blood or sputum
- Wheezing or hoarseness
- Persistent chest pain gets worse with deep breathing or coughing or laughing
- Respiratory infections like bronchitis or pneumonia which doesn’t go away
- New cough or onset of wheezing
- Shortness of breath
- Feeling tired or weak frequently
- Unexplained weight loss and loss of appetite
If cancer spreads to other parts of the body, it may cause the following symptoms and syndromes
- Jaundice (yellowing of eyes and skin) if it spreads to the liver
- Bone pain, usually in the backbone, thigh bones (femur), pelvic region and ribs
- If it spreads to the brain or spinal cord, it can cause headache, weakness, numbness of limbs, problems with vision etc.
- Cancers of the top part of the lungs can cause Horner Syndrome characterized by drooping of one eyelid, reduced sweating on one side of the face etc.
Lung cancer is of two types, depending on the type of cells that constitute cancer: Small Cell Lung Cancer (SCLC) and Non-Small Cell Lung Cancer (NSCLC).
SMALL CELL LUNG CANCER (SCLC)
SCLC occurs in about 20 per cent of the cases of lung cancer and is the most aggressive and fastest-growing of all lung cancers. Often, by the time it is discovered, it would have already spread to other parts of the body. It is also known as Oat Cell Carcinomas. It is more likely to respond to chemotherapy, but less likely to be cured with treatment.
In Limited-stage SCLC, cancer cells are found in one lung and may be found in the tissues between the lungs and in nearby lymph nodes. If cancer is found in the other lung, in the lymph nodes of the other lung, or other parts of the body, it is called Extensive-stage.
Risk Factors and Causes:
The risk factors for SCLC are as follows:
- Tobacco Smoke: About 80% of the deaths caused due to lung cancer are the result of smoking, and this percentage is even higher for SCLC. Smokers are at a greater risk of developing SCLC than non-smokers. Even second-hand smoke can increase the risk of developing lung cancer.
- Air Pollution: Continuous, long-term exposure to polluted air emitted from automobiles, factories etc. increases the risk of lung cancer slightly.
- Exposure to asbestos: People who are regularly exposed to asbestos, for example, those working in mines, mills, textile plants, shipyards etc. are at a greater risk of developing a type of cancer known as Mesothelioma, which starts in the inner lining of the chest cavity and the outer lining called the pleura.
- Exposure to Radon: Radon is a radioactive gas that occurs naturally when uranium in the soil and rocks break down. This invisible, tasteless and odourless gas exposes the lungs to small amounts of radiation and increases the risk of lung cancer.
- Exposure to arsenic and other carcinogens: People who are exposed to substances like arsenic, chromium, nickel, other aromatic hydrocarbons, diesel exhaust etc. are more susceptible to lung cancer.
- Personal or family history: A person who has already had lung cancer is at a very high risk of developing another lung cancer. Genetics also plays an important role in the possibility of getting this condition.
NON-SMALL CELL LUNG CANCER (NSCLC):
NSCLC are the most common lung cancers, which can be divided into several main types based on the type of cells found in the tumour. There are different subtypes of NSCLC. They are:
- Adenocarcinoma: These cancers usually originate in the cells that secrete substances like mucus. It mostly occurs in current or former smokers, and also in non-smokers. It is more common in women than men.
- Squamous cell (epidermoid) carcinoma: These start in the squamous cells, which are the flat cells lining the insides of the airways in the lungs.
- Large cell (undifferentiated) carcinoma: They can appear in any part of the lung and tend to grow and spread quickly, which makes it harder to treat.
DIAGNOSIS OF LUNG CANCER:
The diagnosis usually starts with the doctor asking a list of questions about the symptoms, medical and personal history, lifestyle etc. of the individual. Doctors use a wide range of diagnostic procedures and tests to diagnose lung cancer. Some of them are:
- Chest X-ray: This procedure is carried out to detect the causes of respiratory symptoms,
- Scanning: In case of severe symptoms, CT scan (Computerized Tomography) or MRI (Magnetic Resonance Imaging) may be performed to help determine the stage of cancer and also its spread to other organs and lymph nodes.
- PET (Proton Emission Tomography): This can be used to find out if a tumour tissue is actively growing and determining the type of cells within the tumour.
- Sputum Testing: This is a simple test where the cells in the sputum are examined to check if they are cancerous. This is not a completely reliable method though.
- Bronchoscopy: In this method, the airways are examined through a thin, fiber-optic cable inserted through the nose or mouth to reveal the areas of tumour and the extent of tumour.
- Needle Biopsy: Fine-needle aspiration (FNA), usually performed with radiological imaging for guidance can be useful in retrieving cells for diagnosis. The needle is inserted through the chest wall and into the tumour.
- Thoracentesis: In this procedure, a sample of the fluid is removed from the pleural cavity surrounding the lungs, which is important for the staging and diagnosis of this disease.
- Surgical procedures: There are two surgical procedures which are performed. In a Thoracotomy, the chest is opened and the tumour is removed and examined. It may not be possible to remove the entire tumour if it has spread outside the lungs. Mediastinoscopy is another endoscopic procedure which involves examining the chest cavity between the lungs through a surgically inserted probe to collect the sample of lymph nodes so they can be evaluated for cancer cells. This procedure is useful in determining if the tumour can be surgically removed or not.
LUNG CANCER PROGRESSION AND STAGING:
The staging of lung cancer refers to the extent of the disease. In the case of the NSCLC, it is staged according to the size of the tumour and whether it has spread to the lymph nodes or other organs of the body.
In the Occult or Hidden Stage, cancer cells are found in the coughed-up mucus or in other lung fluids, but no tumour can be seen in the lungs.
Stage 0 is not considered invasive because the cancer cells are found in the innermost lining of the air passages, but have not grown through it.
Stage 1A is considered invasive cancer because the tumour has grown through the inner lining of the airways into the deep lung tissue. The size of the tumour doesn’t exceed 3 cm and has not spread to the bronchi, lymph nodes or distant sites.
In Stage 1B, the diameter of the tumour exceeds 3 cm, or has spread to the main bronchus, or has grown through the lung into the inner layer of the pleura.
In Stage 2A, the tumour is no more than 3 across, but it has spread to the nearby lymph nodes on the same side of the chest as the tumour.
In Stage 2B, there are two scenarios that can occur. One, where the cancer cells have not spread to nearby lymph nodes, but have spread to other parts of the body like the chest wall, diaphragm etc. In the second scenario, cancer has spread to the nearby lymph nodes on the same side of the chest as the tumour. Also the size of the tumour exceeds 3 cm.
In Stage 3A, the tumour may be of any size and cancer has spread to more lymph nodes on the same side of the chest and to other nearby structures, but not the trachea.
In Stage 3B, the tumour may be of any size, and has spread to the lymph nodes on the other side of the chest or above the collar bone, and may have spread to nearby structures like the heart, major heart vessels, diaphragm, chest wall, trachea, oesophagus, breastbone, or to more than one place in the same lung.
In Stage 4, cancer has spread to other lobes of the same lung and to other parts of the body such as the brain, liver, kidneys, adrenal glands or bones.
Treatment options include local therapies such as
- Surgery
- Radiation Therapy
- Chemotherapy
- Targeted Therapy
The patient may receive one or a combination of the treatments. There are several surgical options depending on the type and stage of cancer. During a Wedge Resection, the tumour and a small margin of healthy tissue are removed. In a Lobectomy, one lobe of the lung is removed. During a Pneumonectomy, the surgeon removes the entire lung. In a Sleeve Resection, the diseased section of a large airway is removed, and the healthy ends are reattached. During any of these procedures, the surgeon may remove the lymph to check them for signs of cancer.
Radiation therapy is a local treatment that uses high energy rays to kill or shrink cancer cells to relieve symptoms. External Beam Radiation Therapy (EBRT) is directed at cancer’s location from a machine outside your body. Brachytherapy is used to help remove blockages of the large airways by cancer. Chemotherapy is a systemic treatment that uses drugs to stop the growth of cancer cells by either killing them or inhibiting their cell division. Targeted therapies are newer cancer treatments that work by focusing on specific genetic abnormalities of cancer cells.
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