Some lung cancers are diagnosed early because they are found by accident as a result of tests for other medical conditions. For example, lung cancer may be found by imaging tests (such as a chest x-ray or chest CT scan), bronchoscopy (viewing the inside of lung airways through a flexible lighted tube), or sputum exam (microscopic examination of cells in coughed up phlegm) done for other reasons in patients with heart disease, pneumonia, or other lung conditions. A small portion of these patients do very well and may be cured of lung cancer.
Screening is the use of tests or exams to detect a disease in people without symptoms of that disease. Doctors have looked for many years for a test to find lung cancer early and help people live longer, but only in recent years has a study shown that a lung cancer screening test can help lower the risk of dying from this disease.
The National Lung Screening Trial
The National Lung Screening Trial (NLST) was a large clinical trial that looked at using a type of CT scan known as low-dose CT (sometimes called low-dose spiral or helical CT) to screen for lung cancer. CT scans of the chest provide more detailed pictures than chest x-rays and are better at finding small abnormalities in the lungs. (Both of these tests are discussed in more detail in the section “Exams and tests to look for lung cancer.”) Low-dose CT (LDCT) of the chest uses lower amounts of radiation than a standard chest CT and does not require the use of intravenous (IV) contrast dye.
The NLST compared LDCT of the chest to chest x-rays in people at high risk of lung cancer to see if these scans could help lower the risk of dying from lung cancer. The study included more than 50,000 people aged 55 to 74 who were current or former smokers and were in fairly good health. To be in the study, they had to have at least a 30 pack-year history of smoking. A pack-year is the number of cigarette packs smoked each day multiplied by the number of years a person has smoked. Someone who smoked a pack of cigarettes per day for 30 years has a 30 pack-year smoking history, as does someone who smoked 2 packs a day for 10 years and then a pack a day for another 10 years. Former smokers could enter the study if they had quit within the past 15 years. The study did not include people if they had a prior history of lung cancer or lung cancer symptoms, if they had part of a lung removed, if they needed to be on oxygen at home to help them breathe, or if they had other serious medical problems.
People in the study got either 3 LDCT scans or 3 chest x-rays, each a year apart, to look for abnormal areas in the lungs that might be cancer. After several years, the study found that people who got LDCT had a 16% lower chance of dying from lung cancer than those who got chest x-rays. They were also 7% less likely to die overall (from any cause) than those who got chest x-rays.
Screening with LDCT was also shown to have some downsides that need to be considered. One drawback of this test is that it also finds a lot of abnormalities that have to be checked out with more tests, but turn out not to be cancer. (About 1 out of 4 CT scans in the NLST showed such a finding.) This may lead to additional tests such as other CT scans or more invasive tests such as needle biopsies or even surgery to remove a portion of lung in some people. These tests can sometimes lead to complications (like a collapsed lung) or rarely, death, even in people who do not have cancer (or who have very early stage cancer).
LDCTs also expose people to a small amount of radiation with each test. It is less than the dose from a standard CT, but it is more than the dose from a chest x-ray. Some people who are screened may end up needing further CT scans, which means more radiation exposure. When done in tens of thousands of people, this radiation may cause a few people to develop breast, lung, or thyroid cancers later on.
The NLST was a large study, but it left some questions that still need to be answered. For example, it’s not clear if screening with LDCT scans would have the same effect on people different from those allowed in the study, such as those who smoke less (or not at all), or people younger than age 55 or older than 74. Also, in the NLST, patients got a total of 3 scans over 2 years. It’s not yet clear what the effect would be if people were screened for longer than 2 years.
These factors, and others, need to be taken into account by people and their doctors who are considering whether or not screening with LDCT scans is right for them.
Signs and Symptoms of Lung Cancer
Most lung cancers do not cause any symptoms until they have spread too far to be cured, but symptoms do occur in some people with early lung cancer. If you go to your doctor when you first notice symptoms, your cancer might be diagnosed at an earlier stage, when treatment is more likely to be effective. The most common symptoms of lung cancer are:
- A cough that does not go away or gets worse
- Chest pain that is often worse with deep breathing, coughing, or laughing
- Weight loss and loss of appetite
- Coughing up blood or rust-colored sputum (spit or phlegm)
- Shortness of breath
- Feeling tired or weak
- Infections such as bronchitis and pneumonia that don’t go away or keep coming back
- New onset of wheezing
If lung cancer spreads to distant organs, it may cause:
- Bone pain (like pain in the back or hips)
- Nervous system changes (such as headache, weakness or numbness of an arm or leg, dizziness, balance problems, or seizures), from cancer spread to the brain or spinal cord
- Yellowing of the skin and eyes (jaundice), from cancer spread to the liver
- Lumps near the surface of the body, due to cancer spreading to the skin or to lymph nodes (collections of immune system cells), such as those in the neck or above the collarbone
Most of the symptoms listed above are more likely to be caused by conditions other than lung cancer. Still, if you have any of these problems, it’s important to see your doctor right away so the cause can be found and treated, if needed.
Some lung cancers can cause a group of very specific symptoms. These are often described as syndromes.
Cancers of the top part of the lungs (sometimes called Pancoast tumors) may damage a nerve that passes from the upper chest into your neck. This can cause severe shoulder pain. Sometimes these tumors can affect certain nerves to the eye and part of the face, causing a group of symptoms called Horner syndrome:
- Drooping or weakness of one eyelid
- Having a smaller pupil (dark part in the center of the eye) in the same eye
- Reduced or absent sweating on the same side of the face
Conditions other than lung cancer can also cause Horner syndrome.
Superiour Vena Cava Syndrome
The superior vena cava (SVC) is a large vein that carries blood from the head and arms back to the heart. It passes next to the upper part of the right lung and the lymph nodes inside the chest. Tumors in this area may push on the SVC, which can cause the blood to back up in the veins. This can cause swelling in the face, neck, arms, and upper chest (sometimes with a bluish-red skin color). It can also cause headaches, dizziness, and a change in consciousness if it affects the brain. While SVC syndrome can develop gradually over time, in some cases it can become life-threatening, and needs to be treated right away.
Some lung cancers can make hormone-like substances that enter the bloodstream and cause problems with distant tissues and organs, even though the cancer has not spread to those tissues or organs. These problems are called paraneoplastic syndromes. Sometimes these syndromes may be the first symptoms of lung cancer. Because the symptoms affect organs besides the lungs, patients and their doctors may suspect at first that a disease other than lung cancer is causing them.
Some of the more common paraneoplastic syndromes associated with small cell lung cancer (SCLC) are:
SIADH (syndrome of inappropriate anti-diuretic hormone): In this condition, the cancer cells make a hormone (ADH) that causes the kidneys to retain water. This causes salt levels in the blood to become very low. Symptoms of SIADH can include fatigue, loss of appetite, muscle weakness or cramps, nausea, vomiting, restlessness, and confusion. Without treatment, severe cases may lead to seizures and coma.
Cushing syndrome: In some cases, lung cancer cells may make ACTH, a hormone that causes the adrenal glands to secrete cortisol. This can lead to symptoms such as weight gain, easy bruising, weakness, drowsiness, and fluid retention. Cushing syndrome can also cause high blood pressure and high blood sugar levels (or even diabetes).
Neurologic problems: Small cell lung cancer can sometimes cause the body’s immune system to attack parts of the nervous system, which can lead to problems. One example is a muscle disorder called the Lambert-Eaton syndrome. In this syndrome, muscles around the hips become weak. One of the first signs may be trouble getting up from a sitting position. Later, muscles around the shoulder may become weak. A rarer problem is paraneoplastic cerebellar degeneration, which can cause loss of balance and unsteadiness in arm and leg movement, as well as trouble speaking or swallowing. SCLC can also cause other nervous system problems, such as muscle weakness, sensation changes, vision problems, or even changes in behavior.
Some of the more common paraneoplastic syndromes that can be caused by non-small cell lung cancer (NSCLC) include:
- High blood calcium levels (hypercalcemia), which can cause frequent urination, thirst, constipation, nausea, vomiting, belly pain, weakness, fatigue, dizziness, confusion, and other nervous system problems
- Excess growth of certain bones, especially those in the finger tips, which is often painful
- Blood clots
- Excess breast growth in men (gynecomastia)
Again, many of the symptoms listed above are more likely to be caused by conditions other than lung cancer. Still, if you have any of these problems, it’s important to see your doctor right away so the cause can be found and treated, if needed.
Exams and Tests to Look for Lung Cancer
If your doctor thinks you might have lung cancer based on the results of a screening test or because of symptoms you are having, he or she will do exams and tests to find out for sure.
Medical History and Physical Exam
Your doctor will want to take a medical history to check for any risk factors and to learn more about any symptoms you are having. Your doctor will also examine you for signs of lung cancer or other health problems.
If the results of the history and physical exam suggest you might have lung cancer, more involved tests will be done (see below).
Tests that Might be Used to Look for Lung Cancer
For this test, a sample of sputum (mucus you cough up from the lungs) is looked at under a microscope to see if it contains cancer cells. The best way to do this is to get early morning samples from you 3 days in a row. This test is more likely to help find cancers that start in the major airways of the lung, such as most small cell lung cancers and squamous cell lung cancers. It may not be as helpful for finding other types of non-small cell lung cancer.
If you have symptoms that might be due to lung cancer, this is often the first test your doctor will do to look for any masses or spots on the lungs. Plain x-rays of your chest can be done at imaging centers, hospitals, and even in some doctors’ offices. If the x-ray is normal, you probably don’t have lung cancer (although some lung cancers may not show up on an x-ray). If something suspicious is seen, your doctor may order more tests.
Computed Tomography (CT) Scan
A CT (or CAT) scan is more likely to show lung tumors than routine chest x-rays. A CT scan can also provide precise information about the size, shape, and position of any lung tumors and can help find enlarged lymph nodes that might contain cancer that has spread from the lung.
The CT scan uses x-rays to produce detailed cross-sectional images of your body. Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around you while you lie on a table. A computer then combines these pictures into images of slices of the part of your body being studied. Unlike a regular x-ray, a CT scan creates detailed images of the soft tissues in the body.
Before the CT scan, you may be asked to drink a contrast solution or you may get an injection of a contrast solution through an IV (intravenous) line. This helps better outline structures in your body. The contrast may cause some flushing (a feeling of warmth, especially in the face). Some people are allergic and get hives. Rarely, more serious reactions like trouble breathing or low blood pressure can occur. Be sure to tell the doctor if you have any allergies or if you ever had a reaction to any contrast material used for x-rays.
A CT scanner has been described as a large donut, with a narrow table that slides in and out of the middle opening. You will need to lie still on the table while the scan is being done. CT scans take longer than regular x-rays, and you might feel a bit confined by the ring while the pictures are being taken.
Further Tests if you Have an Abnormal Screening Test Result
It is common for a low-dose CT scan of the lungs to show small, abnormal areas (called nodules or masses) in the lungs, especially in current or former smokers. Most lung nodules seen on CT scans are not cancer. They are more often the result of old infections, scar tissue, or other causes. But tests are often needed to be sure a nodule is not cancer.
Most often the next step is to get a repeat CT scan to see if the nodule is growing over time. The time between scans might range anywhere from about a month to a year, depending on how likely your doctor thinks it is that the nodule could be cancer. This is based on the size, shape, and location of the nodule, as well as whether it appears to be solid or filled with fluid. If the nodule is larger, your doctor might also want to get another type of imaging test called a positron emission tomography (PET) scan, which can often help tell if it is cancer.
If the second scan shows that the nodule has grown, or if the nodule has other concerning features, your doctor will want to get a sample of it to check it for cancer cells (called a biopsy). This can be done in different ways:
- The doctor might pass a long, thin tube (called a bronchoscope) down your throat and into the airways of your lung to reach the nodule. A small, hollow needle on the end of the bronchoscope can be used to get a sample of the nodule.
- If the nodule is in the outer part of the lung, the doctor might pass a thin, hollow needle through the skin of the chest wall and into the nodule to get a biopsy sample.
- If there is a higher chance that the nodule is cancer (or if the nodule can’t be biopsied with a needle), surgery might be done to remove the nodule and some surrounding lung tissue. Sometimes larger parts of the lung might be removed at the same time as well.
These types of tests, biopsies, and surgeries are described in more detail in the documents Lung Cancer (Non-Small Cell) and Lung Cancer (Small Cell) as are the options for treatment if lung cancer is found.
Further Tests if you Have Possible Signs or Symptoms of Lung Cancer
If your doctor is concerned you might have lung cancer because of signs or symptoms you are having, a chest x-ray or chest CT scan to look for tumors in the lung is likely to be the next step. Other tests that might be done include having you cough up sputum (phlegm) to have it looked at for cancer cells, or having a bronchoscopy, where the doctor puts a long, thin tube down your throat and into your lungs to look for anything abnormal.
If any of these tests are suspicious for cancer, further tests such as a biopsy or even surgery will likely be needed to get samples from any tumors.