Lung cancer (cancer of the lung) is common worldwide. Around 8 in 10 cases develop in people over the age of 60 years, usually in smokers. If lung cancer is diagnosed at an early stage, there is a chance of a cure. In general, the more advanced the cancer (the more it has grown and spread), the less chance that treatment will be curative. However, treatment can often slow the progress of the cancer.

Primary lung cancers arise from cells in the lung. There are several types of primary lung cancer. The two most common types are called small-cell lung carcinoma (SCLC) and non-small-cell lung carcinoma (NSCLC). NSCLCs include squamous cell cancers (the most common type of lung cancer), adenocarcinoma and large-cell carcinoma. About 1 in 5 cases of lung cancer are SCLC; the remainder is NSCLC. All these types of lung cancer arise from various cells which line the airways (bronchi). There are some other rarer types of primary lung cancer which arise from other types of cells in the lung. Each type of lung cancer has different properties. For example, small-cell carcinoma grows and spreads (metastasises) rapidly. By the time small-cell cancer is diagnosed, in most cases it has already spread to other parts of the body. In contrast, a squamous cell carcinoma tends to grow more slowly and may not spread to other parts of the body for some time. Secondary lung cancers (or lung metastases) are tumours which have spread to the lung from another cancer somewhere else in the body. The lung is a common site for metastases from other cancers. This is because all blood flows through the lungs and may contain tumour cells from any other part of the body.

A cancerous tumour starts from one abnormal cell. It is thought that something damages or alters certain genes in the cell. This makes the cell abnormal and multiply out of control. Certain risk factors increase the chance of certain cancers forming. See separate leaflet called What Causes Cancer? for more details. Smoking is a major risk factor and is the main cause of lung cancer. Chemicals in tobacco smoke are carcinogens. These are substances which can damage cells and lead to cancer developing. About 9 in 10 cases of lung cancer are caused by smoking. Compared with non-smokers, those who smoke between 1-14 cigarettes a day have eight times the risk of dying from lung cancer. Those who smoke 25 or more cigarettes a day have 25 times the risk. However, the risk of lung cancer depends more on the length of time a person has smoked. So, smoking one pack of cigarettes a day for 40 years is more hazardous than smoking two packs a day for 20 years. After about fifteen years from stopping smoking, that person's risk of developing lung cancer is similar to that of a non-smoker.

Non-smokers have a low risk of developing lung cancer. However, people who are regularly exposed to other people's smoke (passive smokers) have a small increased risk. People who work with certain substances have an increased risk, especially if they also smoke. These substances include radioactive materials, asbestos, nickel and chromium. People who live in areas where there is a high level of background radiation from radon have a small increased risk. Air pollution may be a small risk too. A family history of lung cancer in a first-degree relative (mother, father, brother, sister) slightly increases the risk of lung cancer. But note: most cases of lung cancer do not run in families.

The symptoms of lung cancer can vary between different people. Many people do not have symptoms in the early stages and lung cancer may be diagnosed when a chest X-ray is performed for a different reason. Initial symptoms of lung cancer may include one or more of the following: Persistent cough. Coughing up blood or bloodstained phlegm (sputum). Chest and/or shoulder pains. Tiredness and loss of energy. Weight loss. Shortness of breath or wheezing - especially if a tumour is growing in a main airway and is partially blocking the airflow. Hoarse voice. A change in shape at the end of your fingers (clubbing).

If a doctor suspects that you may have lung cancer, the common initial test is a chest X-ray. This is a simple and quick test and may show changes such as abnormal shadowing. However, a chest X-ray cannot confirm cancer, as there are various other causes of shadowing on a chest X-ray. Other tests are therefore needed.  You may be offered a computerised tomography (CT) scan and other investigations which will help to confirm the diagnosis of lung cancer. You may need other tests which not only provide more information about the cancer but also help to detect whether it has spread. You may be offered different types of tests depending on the circumstances. If the CT scan shows the cancer is at an early stage and you are fit to be treated, you may be asked to have another type of scan. This is called a positron emission tomography-CT (PET-CT) scan. This shows up areas of active cancer and whether it has spread to the lymph glands in the chest. If the cancer has spread to these glands, you will be offered a biopsy. A small sample will be taken and inspected under a microscope to look for the abnormal cells of cancer. The type of cancer can also be determined from the sample.

Assessing the extent and spread is called staging of the cancer. The aim of staging is to find out how much the cancer in the lung has grown, whether the cancer has spread to local lymph nodes or to other areas of the lungs, whether the cancer has spread to other areas of the body (metastasised). By finding out the stage of the cancer, it helps doctors to advise on the best treatment options. It also gives a reasonable indication of outlook (prognosis).

Treatment options which may be considered include surgery, chemotherapy and radiotherapy. The treatment advised for each case depends on various factors, such as the site of the primary tumour in the lung, the type of cancer, the stage of the cancer (how large the cancer is and whether it has spread) and general health.

Treatment may aim to cure the cancer. Some lung cancers can be cured, particularly if they are treated in the early stages of the disease.  Treatment may aim to control the cancer. If a cure is not realistic, with treatment it is often possible to limit the growth or spread of the cancer so that it progresses less rapidly. This may keep you free of symptoms for some time. Treatment may aim to ease symptoms. Even if a cure is not possible, treatments may be used to reduce the size of a cancer, which may ease symptoms such as pain. If a cancer is advanced, you may require treatments such as nutritional supplements, painkillers, or other techniques to help keep you free of pain or other symptoms.

The outlook is best in those who are diagnosed when the cancer is still small and has not spread. Surgical removal of a tumour in an early stage may then give a good chance of cure. However, most people with lung cancer are diagnosed when the cancer has already spread. In this situation a cure is less likely. However, treatment can often slow down the progression of the cancer.

The treatment of cancer is a developing area of medicine. New treatments continue to be developed and the information on outlook above is very general. The specialist who knows your case can give more accurate information about your particular outlook and how well your type and stage of cancer are likely to respond to treatment.