According to the American Cancer Society, lung cancer is the second most common cancer in men and in women, accounting for approximately 13% of all new cancers. The American Cancer Society estimates that 221,200 new cases of lung cancer will be diagnosed in the United States in 2015, and 158,040 patients will die from the disease. Lung cancer is responsible for about 27% of all cancer deaths–more than colon, breast, and prostate cancer deaths combined–and is the leading cause of cancer-related death among men and women in the United States.
Types of Lung Cancer
Lung cancer can be classified into 2 main categories, small-cell lung cancer and non–small-cell lung cancer, also known as NSCLC. It is important to distinguish the exact type of lung cancer to select the best treatment.
Small-cell lung cancer comprises about 10% to 15% of all lung cancers. Small-cell lung cancer is named for the size of the cancer cells when viewed under a microscope; it is also called oat-cell cancer, oat-cell carcinoma, and small-cell undifferentiated carcinoma. The cells in small-cell lung cancer multiply more rapidly than the cells in non–small-cell lung cancer, and form large tumors that can metastasize (spread) throughout the body. Smoking is almost always the cause of this type of lung cancer.
Non–small-cell lung cancer includes about 85% to 90% of all lung cancer cases and can occur in people who have never smoked. This type of lung cancer is divided into 3 main subtypes:
- Adenocarcinoma is the most common type of lung cancer (about 40%). This type occurs mainly in people who smoke or used to smoke, but it is also the most common type of lung cancer in people who have never smoked. Adenocarcinoma is more common in women than in men, and is more likely to occur in younger people compared with other types of lung cancer.
- Squamous-cell (epidermoid) carcinoma includes about 25% to 30% of lung cancer cases. It is strongly associated with tobacco smoking.
- Large-cell (undifferentiated) carcinoma accounts for about 10% to 15% of all lung cancers. It tends to grow and spread more quickly than adenocarcinoma and squamous-cell carcinoma.
The main cause of lung cancer is the use of tobacco products, such as cigarettes, pipes, or cigars. The carcinogens in tobacco cause damage (mutations) to the DNA in lung cells. The more packs of cigarettes a person smokes, and the more years a person smokes, the greater the chance to get lung cancer. When a person stops smoking, the risk for lung cancer is reduced every year, but the risk is still higher than for people who have never smoked. The role of electronic cigarettes in lung cancer is still unclear.
According to the American Cancer Society, 20% of lung cancers (usually adenocarcinoma) occur in people who have never smoked; it is often linked to secondhand smoke or genetics. Exposure to radon, asbestos, air pollution, and other environmental carcinogens can also cause lung cancer.
The symptoms of lung cancer depend on the location of the tumor within the lungs and chest wall. Common symptoms include cough, blood-tinged mucus, shortness of breath, and recurring pneumonia.
As lung cancer grows and spreads, it can obstruct structures within the chest, causing hoarseness, neck swelling, fluid accumulation between the lung and the chest wall, pain, weakness, loss of appetite, and weight loss.
Diagnosis and Screening
Currently, there is no definitive screening method for lung cancer. Several organizations have suggested that people at a high risk for lung cancer (those who are 55-74 years who have smoked 1 pack of cigarettes daily for 30 years or more, and who stopped smoking less than 15 years ago) should have a CT scan screening test.
A physical exam, medical history, and many diagnostic tests are used to diagnose lung cancer. These include:
- Imaging studies: chest x-ray, CT scan, PET scan, MRI, and bone scan
- Staging procedures: bronchoscopy, endobronchial ultrasound, mediastinoscopy
- Evaluation of tissue samples: biopsy and surgical resection pathology, as well as testing for any genetic mutations; lung cancer is typically diagnosed based on a biopsy sample
After a lung cancer diagnosis is confirmed, tests are done to determine if the disease has spread, and the disease stage. The stage of cancer determines the patient’s prognosis and the best approach to treatment.
Lung cancer is divided into 4 stages—stages I and II are considered early stage, and stages III and IV represent advanced stage.
Certain genetic changes (mutations) have been found in lung cancer that can cause lung cancer and affect how a patient responds to therapy. Genetic testing is an important part of diagnosing this disease; if such changes exist, they will affect how the cancer responds to treatment and which therapy is best. Currently, the 2 best known genetic changes associated with lung cancer are EGFR and ALK mutations. Other mutations and pathways, including KRAS and VEGF, are also linked to lung cancer and more are being studied.
Lung Cancer Treatment
There are many treatment options and combinations for lung cancer. A specific treatment plan is selected according to the type of lung cancer, the disease stage, the location of the tumor, and a potential genetic mutation. Evidence shows that identifying a specific genetic mutation in a patient is an important factor for selecting an effective treatment. The most common treatment options for lung cancer are:
Surgery. Resection (removal by surgery) of the tumor. Surgery is usually the main treatment for stage I or II lung cancer
Radiation therapy. If the patient is not a candidate for surgery, radiation therapy is the primary treatment for early-stage disease
Chemotherapy. Preoperative chemotherapy, chemotherapy after surgery with Platinol (cisplatin) or Paraplatin (carboplatin), and maintenance chemotherapy with Alimta (pemetrexed) or Tarceva (erlotinib) is used to delay the progression of lung cancer.
Combination of radiation and chemotherapy. In patients with stage III lung cancer, treatment is usually a combination of chemotherapy and radiation, chemotherapy and surgery, or all 3 therapies.
Stage IV (advanced) lung cancer has been typically treated with chemotherapy, which is not a cure but can increase survival and improve the patient’s quality of life. Surgery and radiation therapy can be used to control symptoms and improve quality of life.
Therapies for Advanced Lung Cancer
Many drugs have been studied for advanced lung cancer, including newer targeted therapies and modulatory drugs that affect the immune system. Immunotherapies stimulate the immune system to reject and kill cancer cells.
Targeted therapies for advanced lung cancer with specific mutations include Tarceva (erlotinib) or Iressa (gefitinib) for EGFR mutations, Xalkori (crizotinib) for ALK mutations, and Avastin (bevacizumab) for VEGF changes. Tagrisso (osimertinib), which is the most recently approved lung cancer treatment, is approved for patients with advanced NSCLC and the EGFR T790M mutation.
- Opdivo (nivolumab) is an immunotherapy approved first for patients with metastatic squamous NSCLC whose cancer has spread after receiving platinum-based (cisplatin or carboplatin) chemotherapy. In October, Opdivo was also approved for patients with nonsquamous NSCLC. Opdivo uses the body’s own immune system to block the lung cancer immune T-cells
- Keytruda (pembrolizumab) is another immunotherapy approved by the FDA in October for patients with metastatic NSCLC that expresses PD-L1 (a certain protein) and has progressed after receiving other treatments. Keytruda helps the immune system fight these types of lung cancer cells. NSCLC that expresses PD-L1 can now be diagnosed with PD-L1 IHC 22C3 pharmDx, the first test designed to detect PD-L1 expression in lung cancer tumors
Other immunotherapies are now being developed for patients with different types of lung cancer.