What Is Small Cell Lung Cancer?

Small cell lung cancer (SCLC) is one of the two types of primary lung cancer, the other one being non-small cell lung cancer. Primary lung cancer is when cancer starts in the lung tissue.

The main cause of small cell lung cancer is tobacco smoking, and its symptoms usually involve persistent coughing and shortness of breath. The initial investigation is a chest X-ray, via your GP and if cancer is suspected, swift transfer to a specialist cancer team is advised. 

This article aims to summarise the most important points in relation to small cell lung cancer. 

Overview

Cancer is the name given when body cells in a specific place, begin to grow out of normal control. This abnormal growth makes it hard for the body to function normally. 

Cancers are named after the place where they start, therefore primary lung cancer, by definition, begins in the lungs. Sometimes cancers can spread around the body in the blood or lymph system which is called metastasis, and this can lead to secondary cancer. 

The lungs are two large organs in the chest, on either side of the heart, which are responsible for breathing in oxygen and exhaling carbon dioxide.

There are two main types of lung cancer:

• Non-small cell lung cancer
• Small cell lung cancer

The names have been given based on how the cells look when placed under a microscope.¹ Non-small cell lung cancer is by far the most common type- accounting for over 80% of lung cancer and small cell lung cancers are therefore much less common. They are different and are treated in different ways. Although small cell lung cancer is rare, it is the more aggressive form of lung cancer, as it grows and spreads (metastasises) faster than non-small cell lung cancer. 

Causes of small cell lung cancer

Certain factors increase your risk of small cell lung cancer. The biggest of these is smoking tobacco. This can be a history of smoking in the past, especially if you started at a young age, even if you have now quit tobacco smoking. Significant exposure to passive smoking is a risk factor, but much less so than actually smoking yourself.²

Other, but less common risk factors include, exposure to hazardous substances such as asbestos, arsenic, chromium, beryllium, nickel, soot, or tar in the workplace.¹ 

Age itself is a risk factor, as it is in many cancers, as lung cancer in general- is rare under the age of 40.¹ A family history of lung cancer, HIV infection, and significant exposure to radiation can be additional risks for the condition.^1,2

Small cell lung cancer is equally common in people assigned female at birth (AFAB) and people assigned male at birth (AMAB). The risk of small cell lung cancer is increased when smoking is combined with other risk factors mentioned above.¹

Signs and symptoms of small cell lung cancer

The most common symptoms are:

• Cough of over 3 weeks duration or a change in a longstanding cough
• Coughing up blood 
• Shortness of breath/wheeze or increased shortness of breath
• Chest or shoulder pain
• Hoarseness
• Loss of appetite
• Weight loss without a known reason
• Fatigue
• Swelling of the face or veins in the neck

Any of the above symptoms should be discussed with a doctor at the earliest opportunity.²

Management and treatment for small cell lung cancer

Your healthcare provider will need to have a thorough discussion of the symptoms with you and perform a physical examination. The doctor will probably perform blood tests and a chest X-ray. Sometimes the GP can also request a CT scan of the chest (detailed comuterised images that uses X-rays).

At this point, if cancer is suspected the GP would refer you to a specialist, and usually the waiting time to see one is less than two weeks. The specialist can then request further investigations such as: 

• Sputum cytology - checking the sputum for cancer cells
• Bronchoscopy - a thin tube with a light and a camera inside is inserted into the windpipe (trachea) and lungs to look for any areas of concern
• Biopsies (removing a piece of tissue to examine under the microscope) - this can be performed during the bronchoscopy

In deciding how best to manage small cell lung cancer, it is important to stage cancer. Typically, lung cancer is graded by the cancer team, by quantifying two factors. Firstly, a measurement of how big the original cancer mass has become within the lung, and this is usually done using a CT scan. Secondly, understanding if the cancer has spread to the other parts  surrounding the lung, lymph nodes (bean-shaped structures of the immune system), or other organs further away from the lung. The specialist team would use an array of imaging options including further CT scans, bone scan (also known as ‘bone scintigraphy’, a scan to check the bones for the spread of cancer), PET scan (3D imaging of the body), and MRI (magnetic resonance imaging). With this information, lung cancer in general is graded into one of 4 stages:

• Stage 1 - cancer no bigger than 4 cm, remains entirely in the lung tissue with no spread - this is called early lung cancer
• Stage 2 - cancer can be any size, but the spread is limited to the other parts of the lung, just outside the lung or nearby lymph nodes
• Stage 3 - cancer can be any size, but spreads  into the other parts of the lung, airway, and areas surrounding the lung
• Stage 4 - cancer can be any size, but it has spread to the opposite lung, around the heart, or other parts of the body such as the brain, liver, or bones

Small-cell lung cancers can be staged as above. However, we do know that small cell lung cancer is much rarer than non-small cell lung cancer and is much more prone to spreading. One study showed that most patients with small cell lung cancer have metastasis at diagnosis with only one-third of patients having cancer that could potentially respond to treatment.³

As a result, doctors often just stage small cell lung cancer into one of two stages: limited stage or extensive stage.⁴

• Limited stage is where cancer cells are seen in one lung and the nearby lymph nodes
• Extensive stage is when the cancer has spread outside the lung to the chest(other lung or lymph nodes further away) or other parts of the body

The treatment for lung cancer is specific to the type of lung cancer and will be decided by a lung cancer multidisciplinary team (MDT). An MDT is a team of different health professionals who work together to plan the most suitable treatment for each patient. The team consists of different health-care specialists including, oncologists (cancer specialists), pathologists (doctors that study body tissues), haematologists (blood disorder specialists), and radiologists (scan and imaging specialists). It can also include nurses, dieticians, occupational therapists, etc.

The cancer specialist team will explain all the treatment options for small cell lung cancer which may involve:

• Surgery- where all or part of one lung is removed. For small cell lung cancer, this is not a common choice, unless the cancer is very small and at a very early stage  
• Chemotherapy - where anti-cancer drugs are used to destroy cancer cells and can be given before or after surgery, before or after radiotherapy, or at the same time as radiotherapy. This is the main treatment for small cell lung cancer
• Radiotherapy - when high-energy rays are used to destroy cancer cells. This is not usually used alone for small cell lung cancer but is used as an addition to chemotherapy, a combination known as chemoradiation. If some small cell lung cancer cells have spread to the brain, radiation can be used to stop them from growing into secondary cancer
• Immunotherapy - harnessing the body’s immune system to boost, direct or restore the body’s natural ability to fight cancer. Although this option is used less in small cell lung cancer than non-small cell lung cancer, increasing progress has been made in this field and the use of this type of medicine has led to some improvements in outcomes for small cell lung cancer patients⁵
• Laser therapy - using a narrow laser beam to kill cancer cells

Choices on small cell lung cancer treatment options will depend on the cancer stage (description of the size of cancer and how far it has spread) and on the patient's age and general health. Small cell lung cancer patients tend to be older, with 44% over the age of 70 at diagnosis. For this reason, they tend to have more comorbidities (presence of other medical conditions) at diagnosis.⁶

Small cell lung cancer can respond to chemotherapy and radiotherapy. However, due to its early treatment resistance and the fact that it has a fast growth rate and early tendencies to spread, the five-year survival rate after the diagnosis is disappointingly low. One study in 2014 showed that patients who had a combination of chemotherapy and radiotherapy had better survival compared to other treatment regimes, however overall median (average) survival from diagnosis was six months for all patients with small cell lung cancer.⁷

FAQs

How is small cell lung cancer diagnosed

If suspected, a GP will perform a blood test, chest X-ray, and possibly a CT scan. If cancer is a possibility from these tests, swift referral to a cancer specialist team to precisely diagnose and manage cancer is the normal practice.

How can I prevent small cell lung cancer

Small cell lung cancer is highly related to smoking tobacco. Although impossible to completely prevent, you can dramatically reduce your risk of developing this condition by not smoking. In addition, minimising the time in which you are exposed to passive smoking and avoiding exposure to certain hazardous substances, such as asbestos and radiation, will further reduce your risk.

How common is small cell lung cancer

Small cell lung cancer accounts for less than 20% of all lung cancers diagnosed. The other 80% are non-small cell cancer which has slightly different treatment and management options. 

Who are at risk of small cell lung cancer

Those people who smoke tobacco, especially those who began smoking at an early age are the main risk group for small cell lung cancer. Also, those who have been exposed in significant quantities to hazardous substances, especially asbestos can have an increased risk of lung cancer generally. AFAB and AMAB have an almost similar risk of small cell lung cancer.

What are the stages of small cell lung cancer

Small cell lung cancer is usually assigned to one of two stages, limited stage or extensive stage. The limited stage is where cancer cells are seen in one lung and the nearby lymph nodes. The extensive stage is when cancer has spread outside the lung to the chest or other parts of the body.

When should I see a doctor

If you have any concerns about your health you should consult a doctor at your earliest convenience. In relation to small cell lung cancer, the most common symptom is cough or shortness of breath/wheeze. However, any concerns over coughing up blood, chest or shoulder pain, hoarseness, loss of appetite, fatigue, or swelling of the face or veins in the neck should be discussed with your doctor as soon as possible. 

Summary

Small cell lung cancer is a type of lung cancer and is highly linked to smoking tobacco. It most commonly presents with cough and/or shortness of breath/wheezing and any of these concerns should be discussed with your GP as soon as possible. The GP will likely request blood tests and chest X-ray, and if cancer is suspected will promptly refer to a cancer team for a thorough assessment. This team will perform the definitive diagnosis and staging of the cancer which determines management and treatment options. Small cell lung cancer is the rarer of the two types of lung cancer but is associated with earlier spread.Therefore, unfortunately it has a poorer response to treatment and shorter survival times following the diagnosis.