Overview
Lung cancer begins in the lungs, which are the two large spongy organs in your chest that supply your blood with oxygen and remove carbon dioxide when you breathe. Lung cancer is the leading cause of cancer deaths worldwide.
There are two main types of lung cancer: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC).
SCLC makes up about 20% of lung cancer diagnoses and is usually attributed to smoking. This type often starts in the epithelial cells of the bronchi and grows quickly into small cell carcinoma or combined small cell carcinoma. Small cell carcinoma is the more common type of the two.
NSCLC makes up the remaining 80% of lung cancer diagnoses. It typically grows at a slower rate than SCLC and can take longer to detect as symptoms are slight until the cancer reaches a late stage. Only about 25% of NSCLC patients are diagnosed while the cancer is still in stage one or two. There are three main types of NSCLC: adenocarcinoma, squamous cell carcinoma, and large-cell undifferentiated carcinoma. Adenocarcinoma makes up the majority of NSCLC diagnoses and is also often attributed to smoking.
According to the CDC, lung cancer causes the most cancer deaths in the United States and worldwide. The rate of lung cancer deaths per 100,000 people in 2018 in the United States was 34.8, almost twice the number of deaths as the next leading type of cancer.
Lung cancer primarily affects the elderly population. Seventy percent of those diagnosed are over 65 years of age. The median age at diagnosis is 70.
As with other forms of cancer, medical professionals use a staging system to classify the severity of the cancer. Stage one lung cancer is confined to the lungs, stages two and three are confined to the chest (stage three involves large or malignant tumors), and stage four denotes lung cancer that has spread to other areas of the body.
Symptoms
Lung cancer has many symptoms, including:
- Heavy coughing that gets steadily worse or doesn’t go away
- Chest pain
- Shortness of breath
- Coughing up blood
- Wheezing
- Fatigue
- Unexplained weight loss
- Bone pain
- Headache
- Frequent respiratory infections
- Difficulty swallowing
If you experience any of these symptoms, you should talk to your doctor right away. It’s important to note that in around 25% of lung cancer diagnoses, there are no apparent symptoms.
Causes
The exact cause of lung cancer is unknown. Cancer forms when the DNA inside certain cells mutates as the cells divide, either due to an inherited or acquired gene mutation. Some mutations are harmless, but other mutations tell the cells to start dividing and growing rapidly, leading to the growth of either a benign or malignant tumor in the lungs.
Risk Factors
Though we don’t know the exact cause of lung cancer, there are several known risk factors, such as:
- Cigarette smoking is by far the leading cause of lung cancer deaths. Approximately 80% of lung cancer deaths are caused by smoking, and a significant number of deaths are attributed to secondhand smoke. Cigarette smoke contains hundreds of known carcinogens that increase the risk of cancer for the smoker and anyone around them.
- Exposure to radiation. If you’ve been treated for cancer elsewhere in your chest with radiation therapy, you have a higher risk of developing lung cancer.
- Exposure to the naturally occurring radioactive gas radon increases your chances of developing lung cancer later on. According to the EPA, radon is the second leading cause of lung cancer after cigarettes.
- Industrial workers exposed to asbestos in the workplace are at high risk of developing lung cancer. Though government regulation has limited the amount of asbestos in our homes and workplaces, it’s still present in many older buildings and can cause several different types of lung cancer.
- Arsenic exposure through drinking water has been shown to increase lung cancer risk in studies of populations of South America and Southeast Asia.
- Carcinogens in the workplace. Exposure to radiation, diesel exhaust, beryllium, cadmium, silica, vinyl chloride, and coal products has been shown to increase the risk of lung cancer.
- Air pollution. Though not as dangerous as smoking cigarettes, it’s estimated that air pollution is responsible for around 5% of lung cancer deaths.
- Family history of the disease. If you or someone in your immediate family, such as your parents or siblings, has had lung cancer, you’re at increased risk of developing the disease yourself.
Survival Rates
Lung cancer has a relatively low survival rate compared to other cancers. This is mainly due to the fact that the majority of lung cancers are not diagnosed until they have reached an advanced stage. More than half of the people that are diagnosed with lung cancer die within a year of the diagnosis.
According to the SEER database maintained by the National Cancer Institute, the combined relative five-year survival rate for lung cancer is 25 percent.
SEER stands for Surveillance, Epidemiology and End Results. The database does not track the stages of lung cancer but rather splits the incidences into three groups:
- The cancer has not spread outside the lung. The survival rate for this group is 63 percent.
- The cancer has spread to nearby structures or lymph nodes. The survival rate for this group is 35 percent.
- The cancer has metastasized to other organs, bones, or the brain. The survival rate for this group is seven percent.
There are many options for treating lung cancer. If the cancer is found early and you are healthy enough for surgery, your doctor might recommend simply removing the diseased portion of the lung. This procedure is called a wedge removal or segmentectomy. If the cancer is more advanced, your doctor may recommend removing an entire lobe of your lung. This surgery is called a lobectomy. Should the doctor recommend removing an entire lung, the surgery is called a pneumonectomy. For very advanced lung cancer, your doctor might recommend other options like radiation therapy or chemotherapy in addition to surgery.