Lung cancer: An overview
Lung cancer is the second most common cancer (excluding skin cancer) in men and women in the United States, but it is by far the leading cause of cancer deaths. More than 500,000 Americans live with lung cancer and 234,030 new cases are diagnosed annually, causing 25 percent of cancer deaths. In fact, lung cancer accounts for more deaths than colon, prostate, and breast cancers combined. 
First, a brief anatomy lesson on your lungs. These cone-shaped, spongy organs are a driving force of your respiratory system. Your lungs are composed of lobes (which funnel oxygen to your blood and release carbon dioxide from your body), bronchi (the main airways extending from your windpipe), bronchioles (tiny extensions of your bronchi), and alveoli (tiny air sacs at the end of your bronchioles). 
Lung cancer forms when abnormal cells in the lungs start to grow rapidly out of control. These cells—which typically start in the lining of the bronchi, bronchioles, or alveoli—can develop into a tumor and spread (or metastasize) to other parts of the body, such as your bones or brain.
Most people are diagnosed with lung cancer when they are older, between the ages of 65 and 74, but the disease can still develop in those younger than 45. While lung cancer is more common in men, particularly African American men, an estimated 1 in 17 women will get lung cancer at some point in their lives. People who smoke also have a much greater risk of developing lung cancer compared to those who have never smoked. Diagnosing lung cancer at its earliest stage is key for effective treatment, but symptoms often appear during a more advanced stage of the disease. 
What are the types of lung cancer?
There are two main types of lung cancer: non-small cell lung cancer (the most common form of lung cancer) and small cell lung cancer (a less common but more aggressive type of lung cancer).
Non-small cell lung cancer (NSCLC)
Non-small cell lung cancer accounts for about 85 percent of lung cancer cases. NSCLC is an umbrella term for several subtypes of lung cancer, but they are often referred to as one group because they have similar treatments.
Mainly occurring in smokers, adenocarcinomas start in young cells that produce substances like mucus, usually forming on the outer areas of the lung. They make up 40 percent of lung cancers, affect more women than men, and often grow slowly.
Squamous cell (epidermoid) carcinoma
This type of NSCLC begins in young squamous cells that make up the inner lining of your airways. Accounting for 25 to 30 percent of lung cancers, squamous cell carcinomas often pop up toward the center of the lungs near the bronchus (a major air passage).
Large cell (undifferentiated) carcinoma
Appearing throughout various parts of the lung, large cell carcinomas tend to grow and spread aggressively, so they are difficult to treat. They make up 10 to 15 percent of lung cancers. 
This rare form of NSCLC only makes up an estimated 0.4 to 4 percent of all lung carcinomas and includes components of both adenocarcinoma and squamous cell carcinoma. It mainly affects older men who have a history of smoking and tends to be difficult to treat. 
This extremely rare NSCLC only accounts for 0.1 to 0.4 percent of lung cancers. These large tumors affect the central airways of the lungs or the outer portion of the chest wall. Most commonly impacting older men and smokers, sarcomatoid carcinomas have a poor prognosis—a 5-year survival rate of only 20 percent. 
These tumors—which make up only 1 to 2 percent of lung cancers—are made up of neuroendocrine cells (cells in the lung that aids in air and blood flow control, growth of other lung cells, and oxygen detection), grow more slowly than other types of lung cancer, and don’t tend to spread. They can form near the center or outer portion of the lungs. 
Small cell lung cancer
Small cell lung cancer is also called oat cell cancer and makes up 10 to 15 percent of lung cancers. These larger tumors typically spread faster than NSCLC and are more common in heavy smokers. Small cell lung cancer commonly begins within the airways in the middle of the chest. 
What causes lung cancer?
An estimated 80 to 90 percent of all lung cancer deaths are attributed to smoking tobacco, and the number is even higher for small cell lung cancers specifically. Still, various factors may increase your risk of lung cancer. 
Smokers are 15 to 30 times more likely to get lung cancer than nonsmokers. Cigarettes, low-tar or “light” cigarettes, cigars, and pipes all cause lung cancer. Quitting smoking reduces your risk, no matter your age.
This naturally occurring gas is the second leading cause of lung cancer in the US and the leading cause among nonsmokers, accounting for 20,000 cases of lung cancer annually. You cannot smell, taste, or see radon, which can build up inside homes.
Even if you never smoke, inhaling secondhand smoke can increase your risk of lung cancer. Experts attribute about 7,300 lung cancer deaths annually to secondhand smoke.
Asbestos and other carcinogens
Workers exposed to asbestos, uranium, arsenic, diesel exhaust, and other cancer-causing substances have greater risk of developing lung cancer. This is particularly true if you also smoke.
Outdoor air pollution has been linked to 29 percent of all deaths and disease from lung cancer globally. This may be due to various particles thrown into the air, such as acids, chemicals, metals, soil, and dust, which can wiggle their way deep into the lungs.
Having a parent, sibling, or child who has been diagnosed with lung cancer increases your risk of the disease. It is unclear if this link is due to secondhand smoke exposure or shared genes, but researchers speculate both may play a role.
What are the symptoms of lung cancer?
Lung cancer often presents no symptoms until the disease reaches a more advanced, harder-to-treat stage. If you experience any of the following symptoms and they do not go away, see your doctor whether or not you smoke, used to smoke, or have never smoked.
- Coughing that doesn’t go away and/or worsens
- Coughing up blood or rust-colored spit
- Chest pain that often worsens with deep breathing
- Chronic infections, such as bronchitis or pneumonia
- Shortness of breath
- Overwhelming fatigue
- Unexplained weight loss
- Swelling in the neck or face
- Bone or joint pain
How is lung cancer diagnosed?
You should ask your doctor about a lung cancer screening if you are a smoker or have smoked in the past, if you are a nonsmoker who has significant secondhand smoke exposure, or if you have family members with minimal or no smoking history who have developed lung cancer, recommends Yolonda Colson, MD, PhD, thoracic surgeon and director of the Women’s Lung Cancer Program at Brigham and Women’s Hospital. 
However, the U.S. Preventive Services Task Force only recommends yearly screening tests—a low-dose CT scan—for people who fit the following high-risk criteria:
- A history of smoking a pack of cigarettes a day for at least 30 years
- Currently smoke or have quit smoking within the past 15 years
- Aged between 55 and 80 years old 
If you don’t qualify for screenings and see your doctor, be prepared to discuss your symptoms and medical history in detail. After a physical exam is performed to check for lumps or other unusual symptoms, one of the following tests may be recommended if he or she suspects lung cancer.
Your doctor will use an X-ray machine to create an image of the bones and organs inside your chest to detect abnormal masses in the lungs.
Also known as CAT cans, this test can detect tumors missed by X-rays and show them in more detail by creating images on a computer.
Your doctor takes a sample of sputum, or the mucus you cough up from your lungs, and then examines it under a microscope to look for cancer cells. It’s best to do this test early in the morning for three consecutive days.
A biopsy can be performed in a few ways to collect a sample of lung cells.
- Bronchoscopy: The doctor puts a long, thin tube down your throat and into your lungs to examine them or take a sample.
- Mediastinoscopy: The surgeon makes a small incision in your middle neck, then inserts tools to collect a sample.
- Needle biopsy: A needle is inserted through the chest wall to get the sample.
“Lung cancer is treatable and is often curable when detected early,” Dr. Colson explains, meaning the disease has not spread yet. “Not all abnormalities on a chest X-ray or chest CT are lung cancer, but if you do have an abnormality, ask your doctor about a follow-up plan or about seeing a lung cancer surgeon or other physician that specializes in lung diseases.” 
How is lung cancer treated?
Your doctor will determine your treatment options based on the type and stage of lung cancer, as well as your overall health. You may also decide that the risks of treatment outweigh the benefits and opt out of treatment. In that case, palliative care may still be beneficial. Treatment options may include:
This option has the best chance to cure NSCLC and may also be used for early stage small cell lung cancer. Varying amounts of tissue may be removed.
- Segmentectomy or wedge resection: A small part of the lobe is removed.
- Segmental resection: A larger portion but still not the entire lobe is removed.
- Lobectomy: The entire lobe of one lung is removed (the right lung has three lobes, the left has two).
- Pneumonectomy: The entire lung is removed.
The surgeon can also do a sleeve resection to remove a piece of the airway if the lung cancer is located there.
Chemo is given through oral or intravenous anti-cancer drugs. Depending on the type and stage of cancer, it may be used before or after surgery, with radiation therapy, or as the main treatment.
This option uses high-energy rays like X-rays to kill cancer cells. During the procedure, you lie on a table while a machine moves around you, emitting the rays at the targeted cells. Radiation may be used before or after surgery, with or after chemo, or as the main treatment.
Typically used for advanced lung cancer, these drugs stimulate your nervous system to fight the cancer.
Targeted drug therapy
These drugs target specific abnormalities in NSCLC cells and are most often used for advanced lung cancer.
Treatments such as yoga, massage, meditation, acupuncture, and hypnosis cannot cure cancer, but may help relieve some symptoms, as well as pain and anxiety. 
Lung cancer complications
Lung cancer can cause some complications, most often due to the fact that the tumor may block airways, cause fluid to build up around the lungs, and/or cause the airway to bleed. Complications include:
- Shortness of breath due to blocked airways or fluid around the lungs
- Coughing up blood from bleeding in the airway
- Pain in the chest, lungs, or other parts of the body
- Fluid in the chest
- Metastasis (the cancer spreads to other body parts) 
How to prevent lung cancer
If you never start, you never have to go through the difficult process of trying to quit.
However, no matter when you quit smoking, doing so reduces your risk of lung cancer. It can take several times to successfully squash the habit for good. Never give up!
Avoid secondhand smoke
Seek out smoke-free environments and don’t allow friends or family members to smoke in your house or car.
Test your home for radon
If radon is detected, you can lower the levels. Check out the United States Environmental Protection Agency for more information on how you can test (and potentially treat) your home for radon.
Limit your exposure to carcinogens
Be aware of cancer-causing chemicals (especially asbestos) at work and follow any employer’s or doctor’s direction to reduce your risk.
Eat lots of fruits and vegetables
Fruits and vegetables are naturally full of nutrients that may fight cancer. Supplements that provide large doses of vitamins or minerals are not recommended, as some studies have found that beta-carotene supplements may increase the risk of lung cancer. 
 https://www.cdc.gov/cancer/lung/basic_info/risk_factors.htm, https://www.lung.org/about-us/blog/2016/06/lung-cancer-and-pollution.html, https://www.who.int/airpollution/ambient/health-impacts/en/, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5351216/, Joseph Treat, MD, professor of medical oncology at Fox Chase Cancer Center with a specialty in lung cancer
 https://www.cdc.gov/cancer/lung/basic_info/symptoms.htm, https://www.cancer.org/cancer/lung-cancer/prevention-and-early-detection/signs-and-symptoms.html, Jake Jacoub, MD, medical oncologist and director of thoracic oncology at MemorialCare Cancer Institute