Definition and Overview
Lung cancer is the most common type of cancer responsible for the most number of cancer deaths in the world. According to the World Health Organisation (WHO), there were approximately 1.69 million lung cancer-related deaths in 2015 alone. The disease develops due to DNA changes that cause the uncontrolled growth of abnormal cells in one or both lungs.
Lung cancer can either be small cell or non-small cell. The latter (NSCLC) is more common, accounting for approximately 85-90% of all lung cancers. However, small cell lung cancer (SCLC) is the more aggressive type and is known to quickly spread to other parts of the body. Due to their distinct differences, SCLC and NSCLC are treated differently.
The majority of SCLC cases are due to smoking. The disease usually starts in the bronchi (airway) where small cancer cells quickly grow and form a malignant tumour that eventually spreads to other parts of the body.
There are three types of SCLC, which are categorised based on how they appear under the microscope. These include:
Small cell carcinoma, also referred to as oat cell cancer
Mixed small cell/large cell carcinoma
Combined small cell carcinoma
Causes of Condition
Both SCLC and NSCLC are linked to cigarette smoking and secondhand smoke. Cigarette smoke contains carcinogens or substances that damage lung tissue. Repeated damage to the lung tissue can cause the cells in the lungs to act abnormally, which can eventually lead to the development of lung cancer.
Other than cigarette smoke, other factors that can increase one’s risk of lung cancer are:
Family history of lung cancer
Exposure to radon gas - Radon is a radioactive gas that forms naturally when certain elements, such as uranium, break down. Uranium can be found in different amounts in rock and soil. It can enter homes or even buildings through crack in walls or floors or gaps in foundations around pumps, wires, and pipes.
Exposure to asbestos, chromium, arsenic, and nickel
Often, small cell lung cancer symptoms do not appear until the disease has already spread to other parts of the body. This makes it difficult for doctors and patients to detect the disease early on or when it is most responsive to treatment. Lung cancer signs and symptoms include:
Progressively worsening cough
Coughing up blood
Chest pain that does not go away
Shortness of breath
Unintended weight loss
Loss or lack of appetite
Swollen face or neck
Chronic infections such as pneumonia and bronchitis
Swelling of lymph nodes
Patients also experience the following symptoms if cancer cells spread to other parts of the body:
Dizziness, seizures, and headaches, if cancer spreads to the brain
Fractures and bone pain, if cancer spreads to the bone
Swelling and jaundice, if cancer spreads to the liver
Who to See and Types of Treatments Available
A chest x-ray is commonly carried out when patients present with symptoms listed above. If any abnormality is detected, imaging tests such as computed tomography (CT) and magnetic resonance imaging (MRI) scans are performed shortly after to gather more information that can help rule out other diseases and make a definitive diagnosis.
Bronchoscopy is also commonly done to assess tumours in the main bronchi and obtain a small tissue sample for testing (biopsy). A needle or open lung biopsy is an alternative to this produce if the tumour is beyond the reach of the bronchoscope. This test helps doctors determine if the tumour is benign or malignant and whether it is small cell or non-small cell lung cancer.
If enlarged lymph nodes are detected, doctors will also perform a lymph node biopsy to determine cancer spread. Other tests, such as bone and PET-CT scans, are performed for cancer staging. Small cell lung cancer staging is crucial in effectively planning the best possible treatment for the patient.
Small cell lung cancer treatment usually combines surgery with chemo, targeted, or radiation therapies. Doctors plan the treatment based on the cancer stage, the patient’s overall health, and possible side effects.
Surgery is performed with the goal to remove the entire tumour as much as possible. This can be achieved with the following operations:
Wedge resection, removes a small section of the lung
Segmental resection, removes a larger portion of the lung
Lobectomy, removes the entire lobe of one lung
Pneumonectomy, removes the entire lung
Chemotherapy and radiation therapy are also standard cancer treatments. They can be used before surgery if the tumour is too big and has to be shrunk or after surgery to kill any cancer cells that remain. They can also be used as part of palliative care to help relieve symptoms.
Small cell lung cancer prognosis has improved since the addition of radiation therapy to treatment. However, the chance of survival remains relatively low when compared to other types of cancers. The five-year survival rate for patients with stage I SCLC is 31% and this number goes down drastically to just 2% when the disease has reached stage IV.
On average, small cell lung cancer life expectancy is between 6 and 12 months upon diagnosis. Without treatment, patients with stage IV of the disease typically live between just two and four months.
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What you need to know about lung cancer. National Cancer Institute. http://www.cancer.gov/publications/patient-education/wyntk-lung-cancer.
Sorenson, M. et al. Small-cell lung cancer: ESMO Clinical Recommendations for diagnosis, treatment, and follow-up. Annals of Oncology. 2009. 20 Suppl 4:71-2.