Lung cancer is a type of cancer that begins in the lungs. It is most frequently diagnosed in people who smoke or have a history of smoking, but non-smokers can develop lung cancer too. Risk factors include smoking, exposure to secondhand smoke, exposure to certain toxins and having a family history of the disease. Lung cancer is the leading cause of cancer-related deaths in the United States.
There are two main types of lung cancer: non-small cell lung cancer and small cell lung cancer. Subtypes of non-small cell lung cancer, especially adenocarcinomas and squamous cell carcinomas, are generally considered slow-spreading and easier to treat. Small cell lung cancer is the more aggressive of the two main types.
There are many treatments available for lung cancer, include surgery, radiation, chemotherapy, targeted therapy and immunotherapy. Ongoing clinical trials are leading to new and better therapies, too. According to data from the American Cancer Society, death rates from lung cancer have decreased by 51% since 1991 for men and 26% for women since 2002.
- Lung Cancer Definition
- Lung Cancer Symptoms and Causes
- Lung Cancer Risk Factors
- Lung Cancer Diagnosis and Treatment
- Lung Cancer Stages and Survival
- Lung Cancer Definitions
What Is the Definition of Lung Cancer?
Lung cancer is a type of cancer that begins in the lungs. It usually starts in the cells that line the bronchi and bronchioles (the increasingly smaller branches of the trachea as it enters the lungs) and the alveoli (the minuscule air sacs at the end of the bronchioles).
There are two main subtypes of lung cancer. According to the American Cancer Society, 80% to 85% of lung cancer cases are non-small cell lung cancer (NSCLC) while 10% to 15% of cases are small cell lung cancer (SCLC). Other less common types of lung cancer comprise the remaining 5% to 10% of cases. While SCLC is responsive to chemotherapy and radiation, it is more aggressive than NSCLC.
What Is Usually the First Sign of Lung Cancer?
Unfortunately, early-stage lung cancer that is confined to the lung often does not produce any discernible signs or symptoms. As a result, symptoms may not present themselves until the disease is more advanced.
However, screening methods for lung cancer, such as low-dose CT scans (LDCT), may be able to detect lung cancer sooner in patients who are at high risk. If you think you may be at high risk for developing lung cancer, ask your doctor if lung cancer screening is right for you.
What Are the Symptoms of Lung Cancer?
Even though it’s uncommon for patients with early-stage lung cancer to experience symptoms, it is important to be aware of the potential signs and symptoms that can occur. While the American Cancer Society notes that many of these symptoms are likely to be caused by something other than lung cancer, any new or concerning symptoms should be discussed with your doctor.
Possible lung cancer symptoms include:
- A cough that persists or gets worse,
- Coughing up blood,
- Chest pain,
- Shortness of breath,
- Persistent respiratory infections (like bronchitis or pneumonia),
- Feeling tired or weak,
- Unexplained weight loss.
In addition, lung cancers can cause symptoms when they involve surrounding structures such as nerves or blood vessels. Cancers located in the upper portion of the lungs, for example, are often referred to as Pancoast tumors. By impinging on nerves in this region, Pancoast tumors can cause a condition known as Horner syndrome, whose symptoms include drooping of one upper eyelid, a smaller pupil in one eye and inability to sweat on one side of the face. Pancoast tumors can also cause pain in the shoulder and arm.
Additionally, cancers located in the upper section of your right lung can cause Superior Vena Cava Syndrome, a condition that occurs when the vein transporting blood from the head and arms to the heart is blocked by growth of the tumor. This can cause swelling of the face, neck, arms or chest as well as lightheadedness and headaches. While these symptoms often develop gradually, they can be life-threatening and require immediate medical attention.
In advanced-stage disease, lung cancer that has spread to other organs within the body, such as the liver or bones, may cause pain or other complications in those areas. Lung cancer that has spread to the brain may cause headaches, weakness, numbness or difficulties with speech.
What is the Cause of Lung Cancer?
Cigarette smoking is the number one cause of lung cancer and is linked to 80% to 90% of lung cancer deaths in the United States. However, non-smokers can develop lung cancer too, and in some cases, there is no clear explanation for why the cells became cancerous. The good news is that experts have identified many risk factors for lung cancer, some of which can be avoided.
What Are the Risk Factors of Lung Cancer?
While there are aspects of lung cancer that are frightening and beyond your control, it’s a disease that has many lifestyle-related risk factors, meaning there are things you can do to mitigate your chances of developing it. Risks factors for lung cancer include:
- Smoking tobacco: According to the Mayo Clinic and other cancer resources, your personal smoking habits are likely the most significant risk factor you can control to avoid lung cancer. The American Cancer Society says that most lung cancer deaths are related to smoking; they also claim that it’s exceedingly rare for a person who has never smoked to develop SCLC.
Smoking cigars, pipes, and light cigarettes increase your chances of developing lung cancer nearly as much as cigarettes — so the less you smoke in general, the better.
- Secondhand smoke: Likewise, simply being around smoking itself, such as living with someone who smokes regularly, can greatly increase your risk level.
- Radon exposure: While you can’t detect it, according to the EPA, radon is the second-leading cause of lung cancer in the country.
- Asbestos exposure: While government regulations have reduced the presence of asbestos in workplaces and commercial products, it’s still harmful when released into the air. Asbestos is a particularly significant risk factor in the development of mesothelioma, a type of cancer that affects the pleura, or lining of the lung.
- Family history: Unfortunately, this is a risk factor you can’t mitigate with lifestyle choices; research has shown if you have a parent, sibling, or child with lung cancer, your chances of developing it are higher.
I’ve Never Smoked. How did I Get Lung Cancer?
Although smoking causes the majority of lung cancer cases — and nearly all instances of small-cell lung cancer — it is not the only way someone can develop the disease. If this is the case for you, you are not alone. The Lung Cancer Research Foundation offers a support line and a patient match program so you can talk to others who know what you’re experiencing and can help you process your diagnosis.
What Percentage of Lung Cancer Is Caused by Smoking?
While different figures exist, the general consensus is that roughly 85% of lung cancer cases are linked to smoking. These percentages are even higher in SCLC.
What Is Lung Cancer Screening?
Screening is the process of undergoing tests to check for abnormalities that may be cancer, only before symptoms occur. It’s considered a preventative measure. Currently, the only recommended screening test for lung cancer is a low-dose computed tomography scan (also called a low-dose CT scan [LDCT]), which provides detailed images of the lungs.
The U.S. Preventative Services Task Force recommends you receive annual screening for lung cancer if you meet all three of the following descriptions:
- You have a history of being a heavy smoker.
- You are currently a smoker, or you quit smoking sometime in the last 15 years.
- You are between the ages of 55 and 85.
How Is Lung Cancer Diagnosed?
While screening is able to catch some cases of lung cancer, the majority are discovered after the disease has already begun to cause symptoms and health issues.
While the only definitive way to diagnose lung cancer is by performing a biopsy and evaluating the tissue in a lab, there are several steps your doctor may take before ordering this procedure. Here’s what you’re likely to experience.
- History & Physical Exam: Your doctor will ask you about some of the symptoms associated with lung cancer and will also examine you for physical signs of the disease, such as irregular sounds in the lungs, a fullness when the doctor taps on your chest, unequal pupils or drooping eyelids, or expanded veins in the chest or neck.
- Chest X-Ray: A chest x-ray is usually the first step following a physical exam in patients who are experiencing respiratory symptoms. If anything abnormal is detected, the additional tests below will likely be scheduled to gain further information.
- CT Chest Scan: CT scans produce higher resolution images of your body than a simple x-ray. Therefore, they provide better visualization of any abnormalities seen on a chest x-ray and are more likely to detect smaller lung tumors.
- PET-CT Scan: PET-CT scans use a radioactive glucose tracer to identify areas within the body where the cancer may have spread.
- MRI Brain Scan: if lung cancer is suspected, magnetic resonance imaging (MRI) may be done to determine if the cancer has spread to the brain.
- Thoracentesis: when fluid collects around the lungs (a condition known as pleural effusion), a sample of this fluid can be removed to ascertain if it is caused by the spread of cancer to the pleura, the lining of the lungs.
- Biopsy: this is the most certain way to determine whether or not there is cancer in the lungs, by taking a sample of lung tissue and reviewing it under a microscope.
I’ve Been Diagnosed with Lung Cancer, Now What?
If you’ve just been diagnosed with lung cancer, there are several treatment options you can pursue. Start by talking to your doctor and asking a few key questions:
- What type of lung cancer do I have?
- What stage of lung cancer do I have?
- Has the cancer spread to other parts of my body?
- What is the recommended treatment approach?
A cancer diagnosis is scary, and it is normal to be concerned. However, there are multiple treatment options available, and ongoing clinical trials are leading to new and better therapies.
What Is the Treatment for Lung Cancer?
Before deciding on a treatment course, ask your doctor if the cancer has been checked for the presence of genetic mutations. This information, along with other factors such as the type of lung cancer you have and its stage, will help you and your doctor develop the right treatment plan for you.
- Surgery: If lung cancer hasn’t spread outside of the lungs, thoracic surgery is considered a strong treatment option. Possible procedures include:
- Wedge resection: Removal of a small section of the lung containing cancerous tissue.
- Segmental resection: Removal of a larger section of the lung, but one that’s smaller than a lung lobe.
- Lobectomy: Removal of the entire lobe of one lung.
- Pneumonectomy: Removal of one entire lung.
- Radiofrequency Ablation: For those with tumors around the outer edges of the lungs — especially if surgery isn’t an option or can’t be tolerated — radiofrequency ablation can use high-energy radio waves and electric currents to destroy tumors.
- Radiation Therapy: High powered x-rays and protons are used in radiation therapy to destroy cancer cells. Radiation therapy can be used alone or in combination with other treatments such as chemotherapy.
- Chemotherapy: Chemotherapy directly kills cancer cells and has widespread use in both early- and advanced-stage lung cancer. It may be used before or after surgery or in combination with radiation if the lung cancer has not spread to other organs or the pleura. If the lung cancer has spread, chemotherapy may be used alone or in combination with immunotherapy.
- Immunotherapy: Drugs that activate your immune system to combat cancer cells are called immunotherapy. Some of these drugs include:
- PD-1/PD-L1 inhibitors: Nivolumab (Opdivo), pembrolizumab (Keytruda), atezolizumab (Tecentriq) and durvalumab (Imfinzi)
- CTLA-4 inhibitors: Ipilimumab (Yervoy)
- Targeted Therapy: Drugs that inhibit specific types of proteins to fight cancer are known as targeted therapies. For lung cancer, this includes drugs like bevacizumab (Avastin) and ramucirumab (Cyramza) that block new blood vessel growth within tumors. Additionally, there is a wide variety of specific medications such as osimertinib (Tagrisso) and alectinib (Alecensa) that can be used against lung cancers that contain specific genetic mutations.
What Are the Stages of Lung Cancer?
Since staging is approached differently for NSCLC versus SCLC, we will explain how it works in each instance separately.
- Non-small cell lung cancer staging: In cases of NSCLC, staging is complex. It relies on the “TNM” system, which classifies lung cancers according to the size of the primary lung tumor (T), the type of lymph nodes involved (N), and the extent of metastasis (M), which is another word for spread beyond the lung. Using this system, stages exist between 0 and IV, with further breakdowns or “stage groupings” along the way.
The stages, in order of least invasive to most invasive, are: 0, IA1, IA2, IA3, IB, IIA, IIB, IIIA, IIIB, IIIC, IVA, IVB. Once your stage is determined, ask your doctor to explain it to you and don’t be afraid to ask for clarification. Staging is complex but it’s important for you to understand.
- Small cell lung cancer staging: While the TNM staging system can still be used for SCLC, it’s more common for doctors to rely on a simpler system made up of two main stages:
- Limited Stage refers to cancer that is only on one side of the chest — which, if spread, has only spread into the lymph nodes located on the same side of the chest — and can be treated with a single radiation field.
- Extensive Stage refers to cancer that has spread through the lung, to both lungs, to other body parts, or to more distant lymph nodes.
What is the Survival Rate for Small Cell Lung Cancer?
Survival rates for small cell lung cancer vary based on if and how far the disease has spread. According to Surveillance, Epidemiology, and End Results (SEER) data, published by the National Cancer Institute, the five-year survival rate from 2009 to 2015 was 6% overall. Much of this has to do with the fact that many lung cancer cases are caught after the disease has already spread. The five-year survival rate for SCLC that is localized to the lung without lymph node involvement or distant spread is higher, at 27%.
The five-year relative survival rates for SCLC by SEER stage:
- Localized: 27%
- Regional: 16%
- Distant: 3%
Keep in mind, these numbers are from 2009-2015. Treatments continue to improve over time and clinical trials are providing hope for new therapies.
What is the Survival Rate for Non-Small Cell Lung Cancer?
According to Surveillance, Epidemiology, and End Results (SEER) data, published by the National Cancer Institute, the five-year survival rate from 2009 to 2015 was 24% overall. For localized forms of the cancer that have not spread to the lymph nodes or beyond the lung, the 5-year survival rate is 61%.
The five-year relative survival rates for NSCLC by SEER stage:
- Localized: 61%
- Regional: 35%
- Distant: 6%
if you’re facing the disease today, you have a variety of effective treatment options. Survival rates have been improving consistently for decades and research and clinical trials are leading to new therapies.
What is the Most Aggressive Form of Lung Cancer?
Small cell lung cancer is the most aggressive form of lung cancer and spreads rapidly. It comprises about 10% to 15% of lung cancer cases and is usually caused by cigarette smoking.
What is Metastatic Lung Cancer?
Metastatic lung cancer refers to when tumors in the lungs spread, or metastasize, to other parts of the body or into the lymph nodes. When lung cancer has metastasized, it is usually classified as a later stage.
Why are Genetic Mutations Important in Lung Cancer?
Many different genetic mutations — when the DNA within your cells is changed or rearranged — have been identified that contribute to lung cancer. These mutations are typically not present at birth but can develop over the course of any person’s lifetime. They are also primarily seen in adenocarcinoma, which is a particular type of NSCLC.
Knowing if genetic mutations are present will help your doctors identify the best course of treatment for you because many of these mutations respond well to targeted therapies. Targeted therapies are primarily used if you have advanced-stage lung cancer that has already spread beyond the lung.
Of note, while a few of the more notable genetic mutations are described below, many others are known and have effective targeted therapy options available.
What is EGFR Positive Lung Cancer?
EGFR stands for epidermal growth factor receptor, and it is a protein involved in cell division and growth. In the case of EGFR positive lung cancer, a mutation develops in the gene for EGFR that causes cells to grow abnormally. These mutations are found more commonly in women, non-smokers and individuals of Asian heritage.
There are multiple treatment options available for patients with EGFR positive lung cancer. Targeted therapies that inhibit EGFR are highly effective and include afatinib (Gilotrif), gefitinib (Iressa), erlotinib (Tarceva), osimertinib (Tagrisso) and dacomitinib (Vizimpro).
What is ALK Positive Lung Cancer?
In ALK-positive lung cancer, the anaplastic lymphoma kinase gene (ALK) and the echinoderm microtubule-associated protein-like 4 gene (EML4) fuse, creating what’s known as an oncogene, or a gene that has mutated and might now cause cancer. ALK oncogenes are found in about one in every 25 cases of NSCLC and are more common in patients who have not smoked. Targeted ALK inhibitors are highly effective, and the majority of patients respond to these treatments for months and often years.
What is KRAS Positive Lung Cancer?
Like ALK, KRAS is a mutated oncogene. It is present in roughly 15% to 20% of NSCLC cases and is more common in patients who have smoked. Although KRAS positive NSCLC has traditionally not responded well to targeted therapies, multiple promising inhibitors are now emerging and are currently being studied in clinical trials.
Who Should Receive Immunotherapy?
Immunotherapy medications now play a major role in the treatment of both small cell and non-small cell lung cancer. Your doctor will likely check to see if your lung cancer expresses the PD-L1 protein, which will help determine the best use of immunotherapy in your treatment. Immunotherapy by itself does not work as well against EGFR or ALK-positive lung cancers. However, targeted therapies do work well in those types of lung cancer.