What is Small Cell Lung Cancer?
Lung cancer ranks as the second most common type of cancer in the United States. It’s also the top cause of cancer-related deaths, responsible for about one-fourth of all such deaths in both men and women. Lung cancer can be categorized into two main types based on cell size and appearance under a microscope – small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). SCLC accounts for around 15% of lung cancer cases, while NSCLC makes up the remaining 85%.
Interestingly, since the late 1980s, the number of lung cancer cases has been on a decline, paralleling a decrease in smoking rates, which is the leading cause of lung cancer. Available treatments for lung cancer include surgery, chemotherapy (drug treatment that kills cancer cells), radiotherapy (use of high-energy radiation to kill cancer cells), and immunotherapy (stimulating the body’s immune system to fight cancer).
The high occurrence of lung cancer in the population calls for better public health initiatives, greater understanding of the role genetics play, and the development of new treatment methods. The aim is to detect and manage the disease more effectively to improve patients’ chances of survival.
What Causes Small Cell Lung Cancer?
Smoking is the main cause of lung cancer, being responsible for about 85% of cases. Other things that can increase your risk of getting lung cancer include second-hand smoke, exposure to asbestos, radon, and other environmental elements.
It’s important to understand that smoking is connected to all forms of lung cancer. But it’s most strongly linked to two types: small cell lung cancer (SCLC) and squamous cell lung cancer.
There are many harmful substances in cigarette smoke that can cause cancer. These include complex chemicals like polycyclic aromatic hydrocarbons (PAHs), aromatic amines, N-nitrosamines, benzene, vinyl chloride, arsenic, and chromium among many others. These are often referred to as carcinogens, which means they can cause cancer.
The amount of smoke exposure and the risk of getting lung cancer are directly related. This means, the more you smoke, the higher your risk of getting lung cancer. Factors such as the kind of cigarette, how long you inhale, and whether the cigarette has a filter can affect the amount of smoke you’re exposed to.
Risk Factors and Frequency for Small Cell Lung Cancer
Lung cancer is the top cause of cancer-related deaths worldwide, claiming about 1.5 million lives in 2012 alone. In the United States, lung cancer contributes to over 200,000 new cases and more than 150,000 deaths every year. Small cell lung cancer (SCLC) accounts for about 15% of these cases.
Smoking is closely linked to lung cancer, especially SCLC. However, over the past four decades, the incidence of SCLC has been on a decline. This is due to a reduction in smoking rates, changes in cigarette manufacturing, and better control of occupational hazards.
Historically, more men have been diagnosed with SCLC than women, but this gap is becoming smaller. In terms of racial demographics, Caucasians have been more prone to SCLC than African Americans, but the survival gap between different racial groups and socio-economic statuses have been closing since 1983.
- The survival rate hasn’t changed radically between 1983 and 2012. It has remained fairly steady.
- In this period, the five-year survival rate has seen a slight increase, rising from 4.9% to 6.4%.
- The median survival time for patients is about 7 months.
- While the overall survival rates have not changed much, younger patients have seen more significant improvements in survival.
Signs and Symptoms of Small Cell Lung Cancer
Small cell lung cancer (SCLC) often affects men who are over the age of 70 and are current or former smokers. These individuals usually have several health issues related to the heart or lungs. SCLC is a serious type of lung cancer that grows rapidly and spreads quickly. Symptoms typically develop swiftly, approximately 8 to 12 weeks before the person seeks medical help.
The signs of SCLC can vary and depend on where the tumor is located and how big it has grown. Common symptoms include:
- Cough
- Wheezing
- Coughing up blood, otherwise known as hemoptysis
- Palpable symptoms due to local tumor growth affecting major blood vessels like the superior vena cava, chest wall, or esophagus
- Neurological issues, recurrent nerve pain, fatigue, and loss of appetite due to extrapulmonary distant spread
About 60% of patients already have metastatic disease at the time of diagnosis. The most common places for the cancer to spread include the brain, liver, adrenal glands, bone, and bone marrow. If the disease is not treated, it typically progresses very rapidly, with an average survival time of just 2 to 4 months.
SCLC is also known to cause “paraneoplastic syndromes”. This is where the cancer causes hormone imbalances or immune reactions affecting other parts of the body. Some of these syndromes include:
- SIADH (syndrome of inappropriate antidiuresis), affecting 15% to 40% of patients, causing weakness, a disruption in taste sensations, and blood volume irregularity
- Ectopic Cushing syndrome in 2% to 5% of patients, involving abnormal corticotropin production that leads to elevated cortisol levels, causing swelling, muscle weakness, and imbalances in blood potassium and pH levels
- Lambert-Eaton Myasthenic syndrome in 3% of patients, causing weakness in the upper arms and thighs, which temporarily improves with exercise, and may also affect the autonomic nervous system
Testing for Small Cell Lung Cancer
If you’re a smoker or a former smoker and you suddenly develop a new cough or start coughing up blood, your doctor will probably want to check if you could have lung cancer. They’ll do this by comparing your new medical images to any previous ones to look for any changes. To confirm if you have lung cancer, you’ll need to go through a detailed examination that includes several imaging tests and a biopsy, which is a procedure to collect small tissue samples for examination.
The first step of the examination includes taking x-rays and conducting high resolution scans of the chest and upper abdomen with a machine called a computed tomography (CT) scanner. Additionally, you might need to have a sophisticated brain scan called an MRI, and a PET/CT scan, which is a special type of scan that can find cancer cells in the body.
Your doctor will also order a range of blood tests to check for the presence of certain substances that can suggest cancer is present. These tests include a complete blood count (CBC), tests to measure the levels of various minerals in your blood (like electrolytes and calcium), tests to check the functioning of your liver (like alkaline phosphatase, alanine aminotransferase (ALT) and aspartate aminotransferase (AST), total bilirubin), and a test to measure the level of a waste product called creatinine in your blood.
Getting an actual sample of tissue from the tumor to examine often depends on where the tumor is located in the body. These biopsy samples are usually collected using either a CT-guided biopsy, which uses images created by a CT scan to help guide the removal of tissue, or a transbronchial biopsy, which is a technique used to sample tissue from your lungs.
Treatment Options for Small Cell Lung Cancer
The treatment for small cell lung cancer (SCLC) is primarily decided based on the stage of the disease. If caught at an early stage, a combination of chemotherapy and radiation therapy may be curative, meaning it can potentially eliminate the cancer. For patients with widespread disease, known as ‘extensive stage’, chemotherapy is the primary treatment. Radiation therapy may be used in certain cases, often to help manage symptoms.
If your SCLC is in a limited stage, meaning it’s found in a smaller, localized area, and you’re in early stages T1-2N0 (indicating that the cancer is in one or both lungs and hasn’t spread to the lymph nodes), you may be eligible for a type of surgery called ‘lobectomy’ where a section of the lung is removed. After surgery, checking the lymph nodes in the chest (mediastinal sampling or dissection) can reveal if the cancer has spread. If there are cancer cells in the lymph nodes, a mix of chemotherapy and radiation treatment is usually employed. For those who can’t undergo surgery for various reasons, a process known as stereotactic ablative body therapy (SABR), which delivers high-dose radiation to the tumor, might be used. This is typically followed by a systemic therapy, generally including a drug called cisplatin.
For the remaining patients in the limited stage, the standard treatment combines chemotherapy and radiation concurrently. The common chemotherapy regimen is cisplatin and etoposide. Implementing radiation alongside chemotherapy has shown promising results – it can boost control over the spread of cancer and improve survival rates. It’s been observed that introducing radiation therapy early on to chemotherapy can further prolong life. Additionally, doctors may recommend prophylactic cranial irradiation (PCI), a type of radiation therapy to the brain to prevent brain metastases (spread of cancer to the brain). PCI has shown significant improvements in survival and reduction in brain tumors.
In extensive-stage SCLC, where cancer has spread to other parts of the body, the primary treatment pathway is systemic chemotherapy. For those patients who respond well to the initial chemotherapy, the next step may be consolidative thoracic radiation therapy. This usually aims to kill any remaining cancer cells in the chest and is typically tolerated well by patients. PCI is also recommended for extensive-stage disease due to its demonstrated survival benefits and preventive role against brain metastases.
Scientists are always on the lookout for better treatments, and a variety of new drugs are currently being explored. These include immunotherapies, which boost your body’s natural defences to fight cancer, and targeted therapies that aim at specific cancer cells. Some of these innovative treatments include Nivolumab, Pembrolizumab, and Ipilimumab (immunotherapies), and Rovalpituzumab tesirine (a targeted therapy).
What else can Small Cell Lung Cancer be?
There are several medical conditions that could potentially be diagnosed when certain symptoms are present. These include the following:
- Hamartoma
- Granuloma
- Lymphoma
- Non-small cell lung cancer
- Carcinoid
Possible Complications When Diagnosed with Small Cell Lung Cancer
Most complications associated with lung cancer arise from the disease itself or from treatments such as chemotherapy and radiation.
There’s also the possibility that patients can develop what are called paraneoplastic syndromes. These may include high levels of calcium in the blood, symptoms resembling a condition called myasthenia gravis, and a condition where the body produces too much antidiuretic hormone known as SIADH.
Common Side Effects:
- Complications from the disease itself or treatments (chemotherapy and radiation)
- Paraneoplastic syndromes
- High levels of calcium in the blood
- Symptoms similar to myasthenia gravis
- Overproduction of antidiuretic hormone (SIADH)
