Lung cancer is the uncontrolled growth of abnormal cells in one or both lungs. These abnormal cells do not carry out the functions of normal lung cells and do not develop into healthy lung tissue. As they grow, the abnormal cells can form tumors and interfere with the functioning of the lung, which provides oxygen to the body via the blood.
According to the World Health Organization (WHO), 7.6 million deaths globally each year are caused by cancer; cancer represents 13% of all global deaths. Lung cancer is by far the number one cancer killer with 1,370,000 deaths per year.
Over the next three decades, female lung cancers will increase thirty-five times faster than male lung cancers, scientists from King’s College London reported in October 2012.
Smoking cigarettes is the single biggest risk factor for lung cancer. It's responsible for more than 85% of all cases.
Tobacco smoke contains more than 60 different toxic substances, which can lead to the development of cancer. These substances are known to be carcinogenic (cancer-producing).
If you smoke more than 25 cigarettes a day, you are 25 times more likely to get lung cancer than a non-smoker.
While smoking cigarettes is the biggest risk factor, using other types of tobacco products can also increase your risk of developing lung cancer and other types of cancer, such as oesophageal cancer and mouth cancer. These products include:
Smoking cannabis has also been linked to an increased risk of lung cancer. Most cannabis smokers mix their cannabis with tobacco. While they tend to smoke less than tobacco smokers, they usually inhale more deeply and hold the smoke in their lungs for longer.
It's been estimated that smoking four joints (homemade cigarettes mixed with cannabis) may be as damaging to the lungs as smoking 20 cigarettes.
Even smoking cannabis without mixing it with tobacco is potentially dangerous. This is because cannabis also contains substances that can cause cancer.
If you don't smoke, frequent exposure to other people’s tobacco smoke (passive smoking) can increase your risk of developing lung cancer.
For example, research has found that non-smoking women who share their house with a smoking partner are 25% more likely to develop lung cancer than non-smoking women who live with a non-smoking partner.
Radon is a naturally occurring radioactive gas that comes from tiny amounts of uranium present in all rocks and soils. It can sometimes be found in buildings.
If radon is breathed in, it can damage your lungs, particularly if you're a smoker. Radon is estimated to be responsible for about 3% of all lung cancer deaths in England.
Exposure to certain chemicals and substances used in several occupations and industries has been linked to a slightly higher risk of developing lung cancer. These chemicals and substances include:
Read more information about asbestosis and silicosis.
Research also suggests that being exposed to large amounts of diesel fumes for many years may increase your risk of developing lung cancer by up to 50%. One study has shown that your risk of developing lung cancer increases by about a third if you live in an area with high levels of nitrogen oxide gases (mostly produced by cars and other vehicles).
It’s important to report any unusual physical feelings to your doctor. Often, these unusual feelings can be attributed to other causes, such as bronchitis. But a doctor should check anything that is unusual or worrisome. The signs and symptoms of lung cancer can take years to develop and they may not appear until the disease is advanced.
Symptoms of lung cancer that are in the chest:
If the original lung cancer has spread, a person may feel symptoms in other places in the body. Common places for lung cancer to spread include other parts of the lungs, lymph nodes, bones, brain, liver, and adrenal glands.
Symptoms of lung cancer that may occur elsewhere in the body:
If lung cancer is suspected as a result of a screening procedure (CT, MRI or PET scan), a small piece of tissue from the lung must be examined under a microscope to look for cancer cells. Called a biopsy, this procedure can be performed in different ways. In some cases, the doctor passes a needle through the skin into the lungs to remove a small piece of tissue; this procedure is often called a needle biopsy.
In other cases, a biopsy may be done during a bronchoscopy. With the patient under sedation, the doctor inserts a small tube through the mouth or nose and into the lungs. The tube, which has a light, small camera and a surgical instrument on the end, allows the doctor to see inside the lung and remove a small tissue sample.
If cancer cells are found in the tissue sample, a genetic test may be performed. The information obtained from the test can help doctors choose the best treatment.
Pathologists (doctors who identify diseases by studying cells and tissues under a microscope) and geneticists (scientists with special training in the study of genes) can give your doctor the information he or she needs to tailor a treatment that will be most effective. These specialists can determine the distinct characteristics of each lung cancer: the tumor type (NSCLC or SCLC, for example); how far it has advanced (its stage); and the mutations (gene changes) that cause or “drive” the cancer.
Besides attacking the tumor, radiotherapy can help to relieve some of the symptoms the tumor causes such as shortness of breath. When used as an initial treatment instead of surgery, radiotherapy may be given alone or combined with chemotherapy. Today, many patients who have a small localized lung cancer, but who are not candidates for surgery, are being treated with a radiation treatment technique known as stereotactic body radiation therapy (SBRT). Patients who are poor candidates for surgery include the elderly, patients with chronic heart failure, and patients receiving a blood thinning drug that puts them at risk of surgical bleeding. SBRT involves treatment with a multitude of small, focused radiation beams tracking the lung tumor along with its respiratory movement, typically in three to five treatments. This treatment delivers very high doses of radiation therapy to the lung cancer in patients where surgery is not an option. SBRT is primarily used in the setting of early stage, localized disease. See the SRS and SBRT page for more information on SBRT.
Most often, radiation therapy is delivered by the external beam technique, which aims a beam of x-rays directly at the tumor. Treatment is given in a series of sessions, or fractions, usually over six to seven weeks for conventional treatments, and over one to five treatments for patients that can be treated with SBRT. For more detailed information see the External Beam Therapy (EBT) page. Three-dimensional conformal radiation therapy or intensity-modulated radiation therapy (IMRT) are fairly new techniques based on a 3-D image of the tumor taken with CT scanning. This image serves as the target for a high-dose radiation beam that can change in shape and size to match the tumor. This method minimizes radiation exposure of nearby normal lung tissue. See the Intensity-Modulated Radiation Therapy (IMRT) page for more information.
In brachytherapy, radiation is delivered directly to the site of disease. This is usually achieved either through a surgical procedure where after resection of the primary tumor radioactive seeds are sutured to the edge of the surgical resection. Also, in the setting of an obstructive tumor within an airway, radiation is delivered to the site of obstruction through plastic tube that is temporarily inserted into the airway. This may help to relieve severe symptoms but does not cure the cancer.
Sources: .radiologyinfo.org, lungcancer.org, nhs.uk, webmd, medicalnewstoday