WHAT IS LUNG CANCER?

The Lungs
The lungs are two sponge-like organs found in the chest cavity. The right lung has three sections, called lobes. The left lung has two lobes. It is smaller because the heart takes up more room on that side of the body. The lungs bring air in and out, taking in oxygen and getting rid of carbon dioxide gas, a waste product of the body.

The lining that surrounds the lungs and helps to protect them and to facilitate the sliding motion during breathing is called the pleura. The chest cavity is called the pleural cavity. The trachea (windpipe) brings air down into the lungs. It divides into tubes called the bronchi, which divide into smaller branches called the bronchioles. At the end of the bronchioles are tiny air sacs known as alveoli.

Most lung cancers start in the lining of the bronchi. Less often, cancers begin in the trachea, bronchioles, or alveoli. Lung cancers are thought to develop over a period of many years. First, there may be areas of precancerous changes in the lung. These changes do not form a mass or tumor. They cannot be seen on an x-ray and they do not cause symptoms. But, researchers are studying new tests to detect precancerous changes by analysis of cells in sputum and by viewing the lining of the airways through a bronchoscope.

If these precancerous changes progress to true cancer, malignant (cancerous) cells begin to grow. The cancer cells may produce chemicals that cause new blood vessels to form nearby. These new blood vessels nourish the cancer cells which can continue to grow and form a tumor large enough to see on x-rays. Cells from the cancer can break away from the original tumor and spread to other parts of the body. This process is called metastasis.
Lung cancer is a life-threatening disease because it often spreads in this way even before it is detected by x-rays.

Types of Lung Cancer
Lung cancer is usually divided into two major types. The first type is small cell lung cancer (SCLC). The second type is non-small cell lung cancer NSCLC. Sometimes a lung cancer may have characteristics of both types. This is called mixed small cell/large cell carcinoma.

Small Cell Lung Cancer (SCLC)
About 20% of all lung cancers are this type. It is named for the size of the cancer cells. Although each of the cells is small, they can multiply quickly and form large tumors, and can spread to lymph nodes and other organs such as the bones, brain, adrenal glands, and liver. This type of cancer often starts in the bronchi and toward the center of the lungs.

Small cell lung cancer is almost always caused by smoking. It is very rare for someone who has never smoked to have small cell lung cancer. Other names for SCLC are oat cell carcinoma and small cell undifferentiated carcinoma.

Non-small Cell Lung Cancer (NSCLC)
This type of cancer accounts for almost 80% of lung cancers. It includes three sub-types. The cells in these sub-types differ in size, shape, and chemical make-up.

Squamous Cell Carcinoma: About 30% of all lung cancers are of this type. It is associated with a history of smoking and tends to be found centrally, near a bronchus.

Adenocarcinoma: This type accounts for about 40% of lung cancers. It is usually found in the outer region of lung. People with one type of adenocarcinoma, known as bronchioloalveolar carcinoma (sometimes called bronchioalveolar carcinoma or bronchoalveolar carcinoma), tend to have a better outlook (prognosis) than those with other types of lung cancer.

Large-Cell Undifferentiated Carcinoma: This type of cancer accounts for about 10% of lung cancers. It may appear in any part of the lung and it tends to grow and spread quickly resulting in a poor prognosis.

Other Types of Lung Cancer
In addition to the two main types of lung cancer, other tumors can occur in the lungs. Some of these are non-cancerous (benign) and others are cancerous (malignant). Carcinoid tumors of the lung account for less than 5% of lung tumors. Most are slow-growing tumors. They are generally cured by surgery. Although some carcinoid tumors can spread, they usually have a better prognosis than small cell or non-small cell lung cancer. Refer to the American Cancer Society document "Lung Carcinoid Tumors" for more information.

There are other, even more rare, lung tumors such as adenoid cystic carcinomas,hamartomas, lymphomas, and sarcomas. Since they are treated in a different way from the common lung cancers, they are not covered in this document.

WHAT ARE THE KEY STATISTICS ABOUT LUNG CANCER?
During 2001, there will be about 169,500 new cases of lung cancer (90,700 among men and 78,800 among women). Lung cancer will account for about 13.4% of all new cancers. The average age of people diagnosed with lung cancer is 60; it is unusual under the age of 40.

Lung cancer is the leading cause of cancer death among both men and women. There will be an estimated 157,400 deaths from lung cancer (90,100 among men and 67,300 among women) in 2001, accounting for 28% of all cancer deaths. More people die of lung cancer than of colon, breast, and prostate cancers combined.

The one-year survival rate (the number of people who live at least one year after their cancer is diagnosed) for lung cancer was 41% in 1995, the last year for which we have national data. This had not changed in ten years. The five-year survival rate for all stages of lung cancer combined was 14% in 1995. This has not changed over many years. For people whose cancer is found and treated early with surgery, before it has spread to lymph nodes or other organs, the average five-year survival rate is about 42%. However, only 15% of people with lung cancer are diagnosed at this early, localized stage. Revised: 4/18/2000

WHAT ARE THE RISK FACTORS FOR LUNG CANCER?
A risk factor is anything that increases a person's chance of getting a disease such as cancer. Different cancers have different risk factors. For example,unprotected exposure to strong sunlight is a risk factor for skin cancer. Several risk factors make a person more likely to develop lung cancer:

Tobacco smoking: By far the most important risk factor is tobacco smoking. At the beginning of the 20th century, lung cancer was rare. The introduction of manufactured cigarettes, which made them readily available,changed this. More than 80% of lung cancers are thought to result from smoking.
The longer a person has been smoking and the more packs per day smoked, the greater the risk. If a person stops smoking before a cancer develops, the damaged lung tissue starts to gradually return to normal.

Even after ten years, the ex-smoker's risk still does not equal the lower risk of a person who never smoked. However, an ex-smoker's risk is about half the risk of people who continue to smoke. Cigar smoking and pipe smoking are almost as likely to cause lung cancer as cigarette smoking. There is no evidence that smoking low tar cigarettes reduces the risk of lung cancer.

Nonsmokers who breathe in the smoke of others (also called second hand smoke or environmental tobacco smoke) are also at increased risk for lung cancer. A nonsmoker who is married to a smoker has a 30% greater risk of developing lung cancer than the spouse of a nonsmoker. Workers who have been exposed to tobacco smoke in the workplace are also more likely to get lung cancer.

Asbestos: Death from lung cancer is about seven times more likely to occur among asbestos workers than among the general population. Exposure to asbestos fibers is an important risk factor for lung cancer. Asbestos workers who smoke have a very high lung cancer risk which is 50 to 90 times greater than that of people in general. Both smokers and nonsmokers exposed to asbestos also have a greater risk of developing a type of cancer which starts from the pleura (the layer of cells that line the outer surface of the lung). This cancer is called mesothelioma. Because it is usually considered a tumor of the pleura and not a type of lung cancer,mesothelioma is discussed in the American Cancer Society document, "Malignant Mesothelioma."

In recent years, the government has nearly stopped the use of asbestos in commercial and industrial products. It is still present in many homes and commercial buildings but is not considered harmful as long as it is not released by deterioration, demolition, or renovation.

Radon: Radon is a radioactive gas produced by the natural breakdown of uranium which cannot be seen, tasted, or smelled. Outdoors, there is so little radon that it is not a danger. But indoors, radon can be more concentrated and become a possible risk for cancer. Recently, concerns have been raised about houses in some parts of the United States built over soil with natural uranium deposits that can create high indoor radon levels.

State and local offices of the Environmental Protection Agency can provide the names of reliable companies that perform radon testing and renovation. High radon levels in some mines can increase the lung cancer risk for miners. Cancer-causing agents in the workplace: In addition to asbestos and radon, there are other carcinogens (cancer-causing agents) in the workplace.

People at risk include miners who may breathe in radioactive ores such as uranium, and workers exposed to chemicals such as arsenic, vinyl chloride,nickel chromates, coal products, mustard gas, and chloromethyl ethers. Even working with fuels such as gasoline might increase a person's risk of developing lung cancer. The government and industry have taken major steps in recent years to protect workers. But the dangers are still present and those who work in these conditions should be very careful to avoid exposure.

Marijuana: Marijuana cigarettes contain more tar than tobacco cigarettes. Also,they are inhaled very deeply and the smoke is held in the lungs for a long time. Marijuana cigarettes are also smoked all the way to the end where tar content is the highest. Many of the cancer-causing substances in tobacco are also found in marijuana. Because marijuana is an illegal substance, it is not possible to control whether it contains fungi, pesticides, and other additives. Medical reports suggest marijuana may cause cancers of the mouth and throat.

The connection between marijuana and lung cancer has been hard to prove because it is not easy to gather information about the use of illegal drugs. Also, many marijuana smokers also smoke tobacco cigarettes. This makes it difficult to know how much of the risk is from tobacco and how much is from marijuana.

Recurring inflammation: Tuberculosis and some types of pneumonia often leave scarred areas on the lung. This scarring increases the risk of the person developing the adenocarcinoma type of lung cancer.

Talcum powder: While no increased risk of lung cancer has been found from the use of cosmetic talcum powder, some studies of talc miners and millers suggest a higher risk of lung cancer and other respiratory diseases from their exposure to industrial grade talc. Talcum powder is made from talc, a mineral that in its natural form may contain asbestos. By law since 1973, all home-use talcum products (baby, body, and facial powders) have been asbestos-free.

Other mineral exposures: People with silicosis and berylliosis (lung diseases caused by breathing in certain minerals) also have an increased risk of lung cancer.

Personal and family history: People who have lung cancer have an increased risk of developing another lung cancer. Brothers, sisters, and children of those who have had lung cancer may have a slightly higher risk of lung cancer themselves. However, it is difficult to say how much of this excess risk is due to inherited factors and how much is due to environmental tobacco smoke.

Diet: Some reports have indicated that a diet low in fruits and vegetables may increase the chances a person may get cancer if they are exposed to tobacco smoke. Evidence is increasing that a diet containing lots of flavonoids (found in apples and onions as well as other fruits and vegetables) may be protective against lung cancer.

Gender: Several studies have shown that the lung cells of women have a genetic predisposition to develop cancer when they are exposed to tobacco smoke. Many doctors think women who smoke or are exposed to tobacco smoke, are more likely to have lung cancer than men.

Air pollution: In some cities, air pollution may slightly increase the risk of lung cancer. This risk is far less than that caused by smoking.

DO WE KNOW WHAT CAUSES LUNG CANCER?
Tobacco smoking is by far the leading cause of lung cancer. Over 80% of lung cancer is caused directly by smoking and some of the rest are due to passive exposure to tobacco smoke. Other risk factors for lung cancer include a family or personal history of lung cancer and exposure to cancer-causing agents in the workplace or the environment.

During the past few years, scientists have made great progress in understanding how these risk factors produce certain changes in the DNA of lung cells, causing the cells to grow abnormally and form cancers. DNA is the genetic material that carries the instructions for nearly everything our cells do. We usually resemble our parents because they passed their DNA on to us. However, DNA affects more than our outward appearance. Some genes (parts of our DNA) contain instructions for controlling when cells grow and divide. Certain genes that promote cell division are called oncogenes.

Others that slow down cell division or cause cells to die at the appropriate time are called tumor suppressor genes. It is known that cancers can be caused by DNA mutations (defects) that activate (turn on) oncogenes or inactivate (turn off) tumor suppressor genes. Some people inherit DNA mutations from their parents that greatly increase their risk for developing breast, ovarian,colorectal and several other cancers.

However inherited oncogene or tumor suppressor gene mutations are not felt to be a cause of very many lung cancers.

Oncogene and tumor suppressor gene mutations related to lung cancer usually develop during life rather than before birth as an inherited mutation. Every time a cell prepares to divide into two new cells, it must duplicate its DNA. This process is not perfect and copying errors may occur.

Fortunately, cells have repair enzymes that proofread the DNA. But, some errors may slip past, especially if the cells are growing rapidly. Acquired mutations in lung cells often result from exposure to cancer-causing chemicals in tobacco smoke. Acquired changes in genes, such as the p53 tumor suppressor gene and the ras oncogene, are thought to be important in the development of lung cancer. Changes of these and similar genes may also be responsible for making some lung cancers likely to grow and invade more rapidly than others. Current research in this field is aimed at developing tests that can detect lung cancers at an early stage by recognizing their DNA changes.
Other researchers are working on gene therapy strategies for repairing or replacing these mutated genes in order to stop the abnormal growth and spread of the cancer cells.

Although lung cancers rarely result from inherited mutations of oncogenes or tumor suppressor genes, some people seem to inherit a reduced ability to detoxify (break down) certain types of cancer-causing chemicals. Others may inherit an increased tendency to activate carcinogens, making them even more dangerous. These people are more sensitive to the cancer-causing effects of tobacco smoke and certain industrial chemicals. Researchers are developing tests that may help identify such people, but these tests are not yet reliable enough for routine use. Therefore, doctors recommend that all people avoid tobacco smoke and hazardous industrial chemicals.

CAN LUNG CANCER BE PREVENTED?
The best way to prevent lung cancer is to not smoke or be around people who do.
People should not start smoking, and those who already smoke should quit.
Everyone should avoid breathing in other people's smoke. People should find out about cancer-causing chemicals they may be exposed to at work and take appropriate protective measures. People who live in areas where natural uranium deposits in the soil release radon gas may consider testing radon levels in their homes.

Nevertheless, some people who get lung cancer do not have any apparent risk factors. Although we know how to prevent over 80% of lung cancers, at this time, it is not possible to give advice on how to prevent all cases of lung cancer.

Revised: 4/18/2000
CAN LUNG CANCER BE FOUND EARLY?
Since symptoms of lung cancer often do not appear until the disease is advanced, only about 15% of the lung cancer cases are found in the early stages before the cancer has spread to nearby lymph nodes or elsewhere. The five-year survival rate for people with lung cancer is about 50% if there is no evidence of cancer in lymph nodes at the time of surgery.

Unfortunately in many others, spread of their cancer has already occurred even if not detected by current medical tests. When all lung cancer stages are considered together the five-year survival rate is only 14%. Many early lung cancers are diagnosed incidentally, meaning they are found as a result of tests that are done for an unrelated medical condition. For example, a diagnosis may be made by imaging tests (such as a chest x-ray or chest CT scan),bronchoscopy (viewing the inside of bronchi through a flexible lighted tube), or sputum cytology (microscopic examination of cells in coughed up phlegm) performed for other reasons in patients with heart disease, pneumonia, or other lung conditions.

Common Signs and Symptoms of Lung Cancer
Although most lung cancers do not cause any symptoms until they have spread too far to be cured, symptoms do occur in some patients with early lung cancer. Prompt attention to symptoms leading to early diagnosis and treatment can result in a cure for some patients. For others, prompt attention to the following symptoms can help them live longer and a with better quality of life:
· A cough that does not go away
· Chest pain, often aggravated by deep breathing
· Hoarseness
· Weight loss and loss of appetite
· Bloody or rust-colored sputum (spit or phlegm)
· Shortness of breath
· Fever without a known reason
· Recurring infections such as bronchitis and pneumonia
· New onset of wheezing

When lung cancer spreads to distant organs, it may cause:
· Bone pain
· Neurologic changes (such as weakness or numbness of a limb, dizziness)
· Jaundice (yellow coloring of the skin and eyes)
· Masses near the surface of the body, due to cancer spreading to the skin or to lymph nodes (collection of immune system cells) in the neck or above the collarbone.

If you have any of these problems, see a doctor right away. These symptoms may be the first warning of a lung cancer. Some of these symptoms can also result from other causes or from noncancerous diseases of the lungs, heart, and other organs. Seeing a doctor is the only way to find out whether or not your symptoms are due to a lung cancer.

Less often, people with lung cancer may have certain syndromes (groups of symptoms and findings detected by examinations or tests).

Horner's Syndrome: Cancer of the upper part of the lungs may damage a nerve that passes from the upper chest into the neck. Doctors sometimes call these cancers Pancoast tumors. Their most common symptom is severe shoulder pain. Sometimes they also cause Horner's syndrome. Horner's syndrome is the medical name for the group of symptoms consisting of drooping or weakness of one eyelid, reduced or absent perspiration on the same side of the face and a smaller pupil (dark part in the center of the eye) on that side.

Paraneoplastic Syndromes: The cells of some lung cancers may produce hormone-like or other substances that enter the blood stream and cause problems with distant tissues and organs, even when the cancer has not spread to those tissues or organs. These problems are called paraneoplastic (Latin for "tumor-related") syndromes. Sometimes these syndromes may occur with early lung cancers and may be the first symptoms of the cancer. Because the symptoms affect other organs, it is common for patients and doctors to suspect at first that they are due to diseases other than lung cancer.

Patients with small cell lung cancer and those with non-small cell lung cancer often have different paraneoplastic syndromes. The most common paraneoplastic syndromes associated with small cell lung cancer are:

· SIADH (abbreviation for syndrome of inappropriate antidiuretic hormone) causes sodium (salt) levels of the blood to become very low. Symptoms of SIADH include fatigue, loss of appetite, muscle weakness or cramps, nausea, vomiting,restlessness and confusion. Without treatment, severe cases may lead to seizures and coma.
· Production of substances that activate the clotting system, causing blood clots to form. Most of these clots occur in the veins of the legs, but they may clog up important vessels and interrupt blood flow to the limbs, lungs, brain, or other internal organs.
· Unexplained loss of balance and unsteadiness in arm and leg movement (cerebellar degeneration).

The most common paraneoplastic syndromes caused by non-small cell lung cancer are:
· Hypercalcemia (high blood calcium levels), causing urinary frequency,constipation, weakness, dizziness, confusion and other nervous system problems.
· Excess growth of certain bones, especially those of the finger tips. The medical term for this is hypertrophic osteoarthropathy.
· Production of substances that activate the clotting system, leading to blood clots.
· Excess breast growth in men. The medical term for this condition is gynecomastia.

Screening Tests for Lung Cancer
Screening is the use of tests or examinations to detect a disease in people without symptoms of that disease. For example, the Pap test is used for cervical cancer screening. Because lung cancer usually spreads beyond the lungs before causing any symptoms, an effective screening program for early detection of lung cancer could save many lives.

Use of chest x-rays and sputum cytology (checking phlegm under the microscope to find cancer cells) was tested several years ago. Most studies concluded that these tests could not find many lung cancers early enough to improve a patient's chance for a cure. For this reason, lung cancer screening is not a routine practice for the general public or even for people at increased risk, such as smokers.

Recently, a new technique of x-ray called spiral or helical low dose CT scanning has been successful in detecting early lung cancers in smokers and former smokers. Whether this will actually save lives has not been proven and studies to answer this important question are in progress. There are also new tests to detect early lung cancers by recognizing changes in the DNA of bronchial cells,which might be useful. However, these tests are still not routinely used. Refer to the section "What's New in Lung Cancer Research and Treatment?" for more information.

HOW IS LUNG CANCER DIAGNOSED?
If there is a reason to suspect you may have lung cancer, the doctor will use one or more methods to find out if the disease is really present. In addition, a biopsy of the lung tissue will confirm the diagnosis of cancer and also give valuable information that will help in making treatment decisions. If these tests find lung cancer, additional tests will be done to find out how far the cancer has spread.

Medical history and physical exam: A medical history (health-related interview) will check for risk factors and symptoms. A physical examination will provide information about signs of lung cancer and other health problems.

Imaging tests: Imaging tests use x-rays, magnetic fields, sound waves or radioactive substances to create pictures of the inside of the body. Several imaging tests are often used to find lung cancer and determine where in the body it may have spread. A chest x-ray is done to look for any mass or spot on the lungs.

Computed tomography (CT scan) will provide more precise information about the size, shape, and position of a tumor, and can help find enlarged lymph nodes that might contain cancer that has spread from the lung. CT scans are more sensitive than a routine chest x-ray in finding early lung cancers.

This test is also used in detecting masses in the liver, adrenal glands, brain and other internal organs that may be affected by the spread of lung cancer. The CT scan involves a special machine that rotates around the body taking x-ray pictures from many angles. A computer then combines their pictures into a very detailed cross-sectional image.

Magnetic resonance imaging (MRI) scans use powerful magnets and radio waves and computers to take detailed cross-sectional images. These images are similar to those produced by CT scanning, and are particularly useful in detecting spread of lung cancer to the brain or spinal cord. Unlike CT scanning, MRI does not involve x-rays.

Positron emission tomography (PET) scans use a sensitive, low dose radioactive tracer that accumulates in cancerous tissues. It has recently received FDA approval for staging of lung cancer.

Bone scans involve injecting a small amount of radioactive substance into a vein. This substance accumulates in abnormal areas of bone that may be due to the spread of cancer. However, other noncancerous bone diseases can also cause abnormal bone scan results. Bone scans are routinely done in patients with SCLC. They are usually done in NSCLC patients only when other test results or symptoms suggest that the cancer has spread to the bones. Sputum cytology: A sample of phlegm is examined under a microscope to see if cancer cells are present.

Needle biopsy: A needle can be guided into the mass while the lungs are being viewed with fluoroscopy (fluoroscopy is like an x-ray, but the image is viewed on a screen rather than on film). CT scans can also be used for needle placement. Unlike fluoroscopy, CT doesn't provide a continuous picture so the needle is inserted in the direction of the mass, a CT image is taken, and the direction of the needle is adjusted based on the image. This process is repeated a few times until the CT image confirms that the needle is within the mass. A sample of the mass is removed and looked at under the microscope to see if cancer cells are present.

Bronchoscopy: After the patient is sedated, a fiberoptic flexible, lighted tube is passed through the mouth into the bronchi (the larger tubes which carry air to the lungs). This can help find centrally-located tumors or blockages in the lungs. It can also be used to take biopsies (samples of tissue) or samples of lung secretions to be examined under a microscope for cancer cells.

Mediastinoscopy: With the patient under general anesthesia (put to sleep), a small cut is made in the neck and a hollow lighted tube is inserted behind the chest bone. Special instruments, operated through this tube, can be used to take a tissue sample from the mediastinal lymph nodes (along the windpipe and the major bronchial tube areas). Looking at the samples under a microscope can show if cancer cells are present.

Bone marrow biopsy: A needle is used to remove a cylindrical core of the bone about 1/16 inch across and 1 inch long. The sample is usually removed from the back of the hip bone and is checked for cancer cells under the microscope.

Blood tests: Certain blood tests are often done to help determine if the lung cancer has spread to the liver or bones and to help diagnose certain paraneoplastic syndromes.

HOW IS LUNG CANCER STAGED?
Staging is the process of finding out how localized or widespread a cancer is. It will show if the cancer has spread to which body structures and how far. The treatment and prognosis (outlook for survival) for a patient with lung cancer depends, to a large extent, on the cancer's stage. The tests described above such as CT, MRI, scans, bone marrow biopsy, mediastinoscopy, and blood tests are used to stage the cancer.

Staging of Non-small Cell Lung Cancer
The system most often used to describe the growth and spread of non-small cell lung cancer (NSCLC) is the TNM staging system, also known as the American Joint Committee on Cancer (AJCC) system. T stands for tumor (its size and how far it has spread within the lung and to nearby organs), N stands for spread to lymph nodes, and M is for metastasis (spread to distant organs). In TNM staging, information about the tumor, lymph nodes, and metastasis is combined and a stage is assigned to specific TNM groupings. The grouped stages are described using Roman numerals from 0 to IV.

Non-small cell lung cancer T stages
Tis: Cancer is found only in the layer of cells lining the air passages. It has not invaded other lung tissues. This stage is also known as carcinoma in situ.

T1: The cancer is no larger than 3 centimeters (slightly less than 1¼ inches),has not spread to the visceral pleura (membranes that surround the lungs), and does not affect the main branches of the bronchi.

T2: The cancer has one or more of the following features:
· it is larger than 3 cm
· it involves a main bronchus, but is not closer than 2 cm (about ¾ inch) to the point where the trachea (windpipe) branches into the left and right main bronchi
· it has spread to the visceral pleura
· the cancer may partially clog the airways, but this has not caused the entire lung to collapse or develop pneumonia

T3: The cancer has one or more of the following features:
· spread to the chest wall, the diaphragm (breathing muscle that separates the chest from the abdomen), the mediastinal pleura (membranes surrounding the space between the two lungs), or parietal pericardium (membranes of the sac surrounding the heart).
· involves a main bronchus and is closer than 2 cm (about ¾ inch) to the point where the trachea (windpipe) branches into the left and right main bronchi, but does not involve this area
· has grown into the airways enough to cause one lung to entirely collapse or to cause pneumonia of the entire lung

T4: The cancer has one or more of the following features:
· spread to the mediastinum (space behind the chest bone and in front of the heart), the heart, the trachea (windpipe), the esophagus (tube connecting the throat to the stomach), the backbone, or the point where the windpipe branches into the left and right main bronchi
· two or more separate tumor nodules are present in the same lobe
· there is a malignant pleural effusion (fluid containing cancer cells in the space surrounding the lung)

Non-small cell lung cancer N stages
N0: No spread to lymph nodes

N1: Spread to lymph nodes within the lung, hilar lymph nodes (located around the area where the bronchus enters the lung). Metastases affect lymph nodes only on the same side as the cancerous lung.

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