Although the past 20 years have brought great progress in treatment, lung cancer remains among the deadliest types of cancer—and also one of the most common. While most cases of lung cancer are linked to smoking cigarettes, there are other causes as well, including exposure to asbestos, radiation, and pollution, or a family history of the condition.

There are two primary types of lung cancer—non-small cell lung cancer (NSCLC), which according to the American Cancer Society (ACS), accounts for 84% of all lung cancer diagnoses; and small cell lung cancer (SCLC), which makes up 13%. Lung carcinoid tumors, lymphomas, sarcomas, and a few other types of lung tumors also make up a small percentage of cases.

Lung cancer is commonly diagnosed among people in their 60s and 70s, particularly in those who have smoked for decades. It is a hard-to-treat form of cancer. Early detection and treatment of lung cancer are equally—and vitally—important to ensure the best outcome.

“We have made great progress in the treatment of lung cancer over the last decade with innovations in immunotherapy and targeted therapies,” says Roy Herbst, MD, PhD, chief of medical oncology at Yale Cancer Center and Smilow Cancer Hospital. “It’s rewarding to know that many of our patients are seeing great benefits. We’re now focused on understanding and overcoming resistance to therapy, so we continue to see long-term benefit and success when caring for our patients.”

Lung cancer refers to different types of cancer that develop within the lungs. Like all cancers, lung cancer begins at the cellular level and causes abnormal cells in the lungs to reproduce rapidly and out of control. Over time, these cells can form a mass of tissue known as a tumor. 

Some tumors are benign, meaning they are not cancerous and do not spread to other parts of the body. Benign tumors can cause symptoms and may require treatment. Other tumors, however, are malignant, or cancerous. The cells that comprise malignant tumors can metastasize, or spread to other parts of the body.  

When a person repeatedly breathes in carcinogenic (cancer-causing) chemicals, it may lead to lung cancer over time. Tobacco products, including cigarettes, cigars, and pipe tobacco, as well as marijuana, contain such chemicals, as do many other substances that some people may encounter in the environment, such as asbestos and diesel exhaust.  

There are different types of lung cancer, including:

• Non-small cell lung cancer. NSCLC is the most common type of lung cancer. NSCLCs are carcinomas, which are cancers of the cells lining the surface of the airways in the lungs. The majority of people with NSCLC cancer are current or previous smokers, but non-smokers may also be diagnosed with this condition. This form of lung cancer progresses more slowly than SCLC, but 40% of NSCLCs will have spread beyond the lungs by the time the disease is diagnosed.
• Small cell lung cancer. Though SCLC is less common than NSCLC, it is more aggressive and rapidly spreads (metastasizes) throughout the body. 

Smoking is the most common cause of lung cancer. But, perhaps surprisingly, many people who smoke never develop lung cancer. It’s believed that people who get lung cancer may have a genetic susceptibility to the condition; people may inherit or acquire genetic mutations that make it easier for cancer cells to multiply uncontrollably within the lungs.  

Continued exposure, either at work or at home, to the following chemicals may cause abnormalities that allow lung cancer to develop:

• Asbestos
• Radon
• Arsenic
• Nickel
• Chromium
• Silica
• Tar
• Diesel exhaust
• Air pollution
• Burning coal 

Most people who are diagnosed with lung cancer experience one or more of the following symptoms:

• Chest pain that flares up while coughing or laughing
• A cough that doesn’t go away and that worsens over time
• Wheezing
• Coughing up bloody mucus
• Difficulty breathing
• Difficulty swallowing
• Hoarseness
• Fatigue
• Unintentional weight loss
• Loss of appetite
• Repeated bouts of bronchitis or pneumonia that don’t respond well to medication

Additional symptoms may be present if the cancer has spread to other parts of the body.

It’s important to note, however, that lung cancer may not cause any symptoms in its early stages.

The most significant risk factor for lung cancer is smoking, which accounts for about 85% of lung cancer cases. In general, the younger a person is when they begin smoking, the more cigarettes they smoke per day—and the longer they continue to smoke, the higher the risk.  

One way to assess a smoker’s risk is to determine the number of his or her “pack-years.” (The term “pack-years” refers to the number of packs of cigarettes a person typically smokes every day. Smoking one pack a day for 20 years—or two packs a day for 10 years—is considered 20 pack-years. Cancer risk rises as the number of pack-years increases.)  

In general, people with at least 20 to 30 pack-years are more likely to develop lung cancer. Smoking cigars and pipes also increases lung cancer risk. It’s important to note that people who smoke can reduce their risk for lung cancer by stopping smoking.   

Repeat exposure to second hand smoke is another risk factor.

To diagnose lung cancer, your doctor will obtain your medical history, perform a physical exam, and order different tests that confirm the presence of the disease.  

If your doctor suspects lung cancer, you’ll be asked such questions as whether you are a current or former smoker, if there’s a family history of lung cancer, if you have had several bouts of bronchitis or pneumonia recently, whether you have been exposed to different chemicals at work, and whether you have previously received radiation therapy to the chest to treat cancer.  

During a physical exam, the doctor will listen to your lungs for signs of wheezing, trouble breathing, absent breath sounds over areas of the lung, or related problems. They will also check for signs of hoarseness and chest discomfort.  

Doctors also may order imaging tests, such as a chest X-ray or computed tomography (CT) scan of the chest or abdomen, to check for the presence of a tumor or mass in the lungs.  

If they believe that lung cancer has spread to other parts of the body, including the brain or bones, they may order the following:

• Magnetic resonance imaging (MRI) scan
• Positron emission tomography (PET) scan, often combined with a CT scan
• Bone scan

To confirm a diagnosis of lung cancer, doctors will check to see if cancer cells are present in:

• Biopsied tissue that has been removed from a suspicious mass on the lung
• Sputum, or mucus that has been coughed up
• Fluid that has collected around the lungs in the pleura
• Biopsied local lymph nodes, to see if the cancer has spread beyond the lungs

There are several techniques for biopsying lung tissue, some of which include:

• Needle biopsy. In this procedure, a CT scan, ultrasound, or other imaging procedures map a path for a needle to penetrate the chest wall to extract a sample of abnormal tissue from the lungs. Pathologists then examine the tissue under a microscope to check for the presence of cancer cells.
• Bronchoscopy. A bronchoscope, a fiberoptic tube equipped with a light, is inserted through the throat and into the lungs. This allows doctors to visually examine lung tissue. If necessary, a tissue sample can be biopsied through the bronchoscope. 
• Mediastinoscopy. In this procedure, an incision is made at the base of the neck and a mediastinoscope, a thin tube equipped with a light and lens, is inserted into the chest behind the breastbone. Doctors can use the mediastinoscope to look at tissues and to biopsy tissue samples from the lymph nodes. 

After a biopsy, a pathologist examines the tissue sample under a microscope to check for the presence of cancer cells. They will determine whether cancer cells are present, and if they are, whether the cancer is non-small cell or small cell. The sample may also be tested for genetic mutations to help guide treatment recommendations. This process can take up to two weeks.  

Patients who are long-term smokers or former smokers may choose to be screened for lung cancer annually, before symptoms develop, via a low-dose CT (LDCT) scan. This imaging test may help to identify lung cancer at an earlier stage, when it is more treatable.

The type of treatment depends on the type of cancer and how advanced it is upon diagnosis.  

For people with non-small cell lung cancer:

• Surgery is the preferred treatment for early-stage disease, to remove the portion of the lung containing cancer. After surgery, doctors may offer chemotherapy with or without radiation therapy to destroy any remaining cancer cells. (Surgery is sometimes not possible due to the location of the tumor or the patient’s overall health.) Different types of surgeries may be used to treat lung cancer, including:

o   Lobectomy. The left lung has two lobes, or sections. The right lung has three lobes. In a lobectomy, a surgeon removes the entire lobe in which the cancer is located.

o   Wedge resection or segmentectomy. In this procedure, rather than removing an entire lobe, the surgeon removes the tumor along with a margin of healthy tissue.

o   Pneumonectomy. In a pneumonectomy, a surgeon removes the entirety of the right or the left lung. This procedure is used if the cancer is near the center of the chest.

o   Sleeve resection. This procedure is used to remove a section of the main bronchus, a tube-like passageway that brings air to the lungs.

• Chemotherapy. For people with more advanced cancer, chemotherapy with or without radiation therapy may help to improve symptoms and quality of life.
• Immunotherapy. Some people with advanced lung cancer that has spread throughout the body may respond well to immunotherapy, which helps boost the body’s immune system.
• Targeted Therapy. Patients with advanced lung cancer may be eligible for targeted therapy, which helps to fight cancer when specific genetic mutations or abnormalities are present.
• Radiation therapy. This treatment kills cancer cells by exposing them to radiation. Radiation may be delivered to the lung by a machine outside the body. This is known as external beam radiation therapy (EBRT). A similar delivery technique called stereotactic body radiation (SBRT) precisely directs high doses of radiation at the tumor. SBRT may be used to treat early-stage lung cancers.

For people with small cell lung cancer, chemotherapy and radiation may help them to live longer with a better quality of life. It’s important to note that treatments are not curative for most people, and the cancer is likely to continue spreading throughout the body.

Lung cancer survival rates vary widely, based on a number of factors. Among people with non-small cell lung cancer, 64% of those whose cancer has not spread outside the lung will live for 5 years or longer. When the cancer spreads locally, the percentage declines to 37%. When non-small cell lung cancer spreads to distant body parts, only 8% of people survive for 5 years.  

Small cell lung cancer is quicker-growing and is often diagnosed later, at a more advanced stage. Among people with small cell lung cancer, only 29% of people survive 5 or more years when the cancer only affects the lungs. When the cancer spreads locally beyond the lungs, that percentage goes down to 18%. And, if the cancer spreads to faraway parts of the body, it goes down further still, to 3%.

While lung cancer remains a serious disease, in recent years, survival rates have been slowly but steadily increasing thanks in large part to research and the development of new therapies, in particular, targeted drugs and immunotherapies.

“Patients cared for by the Center for Thoracic Cancers at Smilow Cancer Hospital and Yale Cancer Center have a multidisciplinary team of experts in lung cancer caring for them each step of the way,” says Dr. Herbst. “In addition to clinical care, each specialty is invested in research to bring the latest advances in lung cancer treatment and care to our patients.”