Asbestos Lung Cancer
Asbestos is a known carcinogen, meaning a substance that causes cancer. Exposure to this mineral can cause both mesothelioma and lung cancer. Both diseases affect the lungs, but they form in different types of tissues, which makes them behave differently.
What is the difference between asbestos-related lung cancer and mesothelioma?
Lung cancer forms in the cells of the lung itself, while malignant mesothelioma forms in the linings around certain organs. Pleural mesothelioma develops in the pleura, which is the lining of the lungs.
Some epidemiology studies have estimated that asbestos-related lung cancer causes twice as many deaths per year as mesothelioma does. Although the incidence of lung cancer overall is much higher than that of mesothelioma, it’s often difficult to be certain about the cause of particular lung cancer cases because there are other factors that increase risk for lung cancer.
Asbestos exposure can also lead to other asbestos-related diseases, such as asbestosis. This is a lung disease in which the presence of asbestos fibers leads to scarring throughout the lung, which eventually interferes with its function and makes breathing difficult. Although asbestosis is not a type of cancer, it’s an indication that a patient had significant asbestos exposure and is at risk for asbestos-related cancers.
How does asbestos cause lung cancer?
Asbestos fibers are very tiny. When they’re present in the air, they can’t be seen or smelled. When a person inhales them, the asbestos fibers can become embedded in the lung tissue.
Asbestos it is not easily broken down, which is why it was so useful in industrial applications. This strength is also the reason asbestos causes illness.
When the fibers enter the lung tissue, the body mounts an immune response to remove them. However, the fibers are so stable that nothing can get rid of them. The body mounts an increasingly strong immune response, which is sustained over many years. This causes damage to the surrounding tissues. It can change the DNA of lung cells, which leads to those cells becoming cancerous.
People with a history of occupational asbestos exposure are at risk of developing asbestos-related diseases or cancer. Their family members may also be at risk because asbestos fibers can be carried home on a worker’s clothing, hair, or skin.
There are two different types of asbestos. Serpentine (also known as chrysotile) asbestos tends to break apart more easily into smaller particles and fibers, and the fibers are curly. Amphibole asbestos (a group that includes the minerals amosite, crocidolite, tremolite, anthophyllite, and actinolite) tends to remain in longer fibers, and these fibers are straight.
Both types of asbestos are associated with lung cancer. This is because the lung tissue is directly exposed to asbestos fibers in the air, so it’s easy for any shape of asbestos fiber to embed itself into the lung tissue. However, the straighter and longer amphibole asbestos fibers are more likely to work their way through the lung tissue into the pleura, so they’re more strongly associated with pleural mesothelioma.
There is no doubt that asbestos exposure is a risk factor for developing lung cancer. A 2019 study showed that asbestos exposure in non-smokers created an increased risk of lung cancer, with the risk being about five times as great as that of non-smokers who were not exposed to asbestos.
People who were exposed to asbestos and who also smoked had about 50 times the risk of lung cancer as nonsmokers with no asbestos exposure.
What are the symptoms of asbestos-related lung cancer?
The symptoms of lung cancer are similar no matter what the cause.
People with lung cancer may experience:
- Persistent cough, which may be dry or sometimes bring up blood
- Chest pain
- Shortness of breath
- Excessive fatigue
- Unexplained weight loss
These symptoms are similar to those of many other respiratory diseases, including pneumonia, asthma, and COPD (emphysema). Other types of cancer, such as mesothelioma or cancer that has spread from another part of the body, may also cause the same symptoms.
How is asbestos-related lung cancer diagnosed?
The process of diagnosing asbestos-related lung cancer usually involves several steps.
These tests use various methods to visualize the inside of the body. The first step in the diagnostic process is often a chest X-ray.
Often, a computerized tomography scan (CT scan) of the chest will be used next, although it’s sometimes the first step. A CT scan also uses X-rays, but gives doctors a more detailed 3D image.
Other types of imaging studies may also be used. An MRI uses large magnets to take detailed images, while a PET scan uses a tracer to check for spread of cancer cells throughout the body.
The definitive diagnosis of cancer requires a biopsy. This is a sample of tissue that’s sent to a pathologist to be examined under a microscope and tested to determine whether the patient has cancer and, if so, what type.
In many lung cancer cases, the sample is obtained through a bronchoscopy. A tube is inserted down the throat and into the lungs, to visualize the area and obtain the biopsy sample.
In some cases, if the tumor is located relatively close to the skin, a transthoracic needle biopsy may be used. A needle is inserted through the chest wall into the lung tissue in order to get the tissue sample.
In some cases, if a patient has a pleural effusion (a buildup of fluid around the lung), a sample of this fluid may contain enough cancer cells for a pathologist to analyze. There are also cases where sputum — a mixture of saliva and mucus — samples are collected and analyzed for cancer cells, although this type of analysis can miss many lung cancer cases.
Types of Lung Cancer
There are two types of lung cancer: small cell lung cancer (SCLC), and non-small cell lung cancer (NSCLC). A pathologist will determine which type the patient has based on the biopsy.
- Small cell lung cancer (SCLC). The cells of SCLC look small and round under the microscope. This type almost always occurs in smokers and is generally harder to treat.
- Non-small cell lung cancer (NSCLC). This includes several subtypes of cancer (adenocarcinoma, squamous cell carcinoma, and large cell carcinoma). The cells of this type are larger, and it’s easier to treat.
Staging of Lung Cancer
The process of staging refers to determining how advanced a cancer is. As part of the process of diagnosis, doctors will also stage the cancer. For different types of cancer, the stage is described in different ways.
For NSCLC, a system of four stages is generally used, with higher numbers indicating more advanced disease.
- Stage I – The cancer is relatively small and is localized to the lung. It has not spread to lymph nodes or other areas of the body.
- Stage II – The cancer has grown to involve additional structures near the lung, and/or has spread to lymph nodes in the chest.
- Stage III – The cancer has grown and spread more widely within the chest, and/or has spread to more distant lymph nodes.
- Stage IV – The cancer has spread to other parts of the body.
There are also substages within each stage, which are indicated by a letter (for example, stage IIA, or stage IIIB). Substages give doctors a more precise indication of where cancer cells are present.
For SCLC, a simpler staging system is usually used, with only two stages:
- Limited – The cancer is in only one lung and possibly the lymph nodes in the mediastinum (the center of the chest).
- Extensive – The cancer has spread beyond the limited stage.
How is a case of lung cancer determined to be asbestos-related?
Knowing exactly what caused a particular case of any cancer can be difficult. This is especially true because many workers who were exposed to asbestos were also smokers.
A few criteria are used for determining whether a particular case of lung cancer is asbestos-related. Some of the features that may be considered include:
- The presence of asbestosis
- Pleural plaques (areas of thickening of the pleura) or other changes in the pleura
- Confirmation of the presence of asbestos fibers in the patient’s lung tissue or fluids
- History of asbestos exposure, at least ten years in the past, which accounts for the latency period between asbestos exposure and the development of cancer
Chrysotile asbestos does not tend to accumulate in lung tissue because the fibers can break apart, and so significant levels of asbestos may not be found when a tissue sample is examined, even if a patient has had high levels of exposure to chrysotile asbestos.
However, patients who have been exposed to amphibole asbestos will often have identifiable asbestos fibers in their lung tissues because the longer fibers tend to embed into tissues and stay there for a long time.
What are the treatment options for asbestos-related lung cancer?
The treatment options for lung cancer don’t change based on what caused the cancer. Asbestos-related lung cancer is treated like any other lung cancer.
Lung cancer is far more common than mesothelioma. Mesothelioma patients often need to travel to a specific cancer center to access an expert on their disease. By contrast, lung cancer patients may not need to travel as far to find experts in medical and surgical oncology who are familiar with their disease. Still, many patients are treated at a cancer center to more easily access all of the health care that they need.
Several treatment options exist for lung cancer patients. Some patients receive treatments intended to remove as much of the cancer as possible, with the goal of extending life. Options may include:
- Surgical removal of the tumor may be an option for patients in an early stage. This may include removing part of a lung (known as a wedge resection or lobectomy), or even a whole lung (pneumonectomy).
- Chemotherapy is an option for patients who are not eligible for surgery. Doctors may also recommend chemotherapy either before surgery (neoadjuvant chemotherapy) to shrink the tumor and make it easier to remove, or after surgery (adjuvant chemotherapy) to kill cancer cells that may not have been removed during the procedure.
- Radiation therapy
- Radiation therapy can target a tumor that can’t be removed surgically, shrink a tumor before surgery, or target any cells that may have been left behind after surgery.
- Immunotherapy is a newer treatment option that stimulates the body’s own immune system to destroy cancer cells. The FDA has approved three immunotherapy drugs (Keytruda, Tecentriq, and Opdivo) for use in certain patients with NSCLC. Immunotherapy can be used either instead of or in addition to chemotherapy.
In many patients, the treatment plan includes using more than one of these types of treatments, to eliminate as many cancer cells as possible.
Some patients receive palliative care, which is aimed at improving quality of life rather than length of life. Patients in more advanced stages may be eligible only for palliative care. Even in earlier stages, some patients choose palliative care, because they prefer to be more comfortable in their remaining time rather than enduring the side effects of aggressive treatments.
Because lung cancer is one of the most common types of cancer in the United States, there are many research studies underway to find better methods of treating this disease. A research study designed to test a new treatment is called a clinical trial.
Some patients choose to enroll in a clinical trial to get access to a cutting-edge new treatment with the potential to extend life or improve quality of life. However, there are no guarantees that the experimental treatment will prove to be better than the existing options.
If you’re considering being part of a trial, you can search the National Cancer Institute’s database of current clinical trials to find those for which you may be eligible. You should also discuss this issue with your oncologist, who can help you weigh the pros and cons of participating.