Lung Cancer and Mesothelioma
Pleural mesothelioma is the most common form of mesothelioma, and as such, is often considered or spoken of as a form of lung cancer, but this is incorrect. Mesothelioma and lung cancer are completely different diseases, with different origin sites, tumor structure and treatability.
Mesothelioma is a cancer that affects the mesothelium, which are the serous membranes that protect and support different organs in the body by secreting fluid that reduces friction and eases movement of those organs within their respective body cavities. Pleural mesothelioma affects the pleural surfaces in the chest cavity. The parietal pleura lines the inner chest wall and the visceral pleura encases the lungs. The fluids secreted by each pleura enable the lungs to move easily when breathing. The tumors can spread to the lungs and invade its inner tissues, but the origin site of the cancer remains the pleura.
The other major form, peritoneal mesothelioma, which affects mesothelial tissue in the peritoneum, can also spread to the lungs, but its origin site remains either the parietal or visceral peritoneum.
Cancer guidelines teach that a tumor which invades another surface is still a form of the original cancer and generally retains its overall structure and behavior. It is because of these guidelines that we speak of mesothelioma as distinct from lung cancer.
Differences Between Mesothelioma and Lung Cancer
Mesothelioma is a diffuse malignancy. It invades a tissue area as a large number of interlocked tumors and the boundaries between malignant tissue and healthy tissue are blurred and, eventually, dissolved. This is the primary reason that mesothelioma remains so difficult to treat. The large extent of malignant tissue makes complete surgical resection very difficult. Chemotherapy is generally unable to inhibit the growth of so many masses, nor is radiation effective over such large areas. In its late stages, the cancer engulfs the invaded tissues, wrapping completely around it and restricting its ability to move.
Lung cancer works differently. It arises within the lungs themselves and is characterized by individualized tumor masses. Even for people with multiple masses, the tumors generally possess clear boundaries. The tumors can grow quite large and in its late stages and most aggressive forms, lung cancer is just as deadly as mesothelioma. However, it is much more amenable to treatment. Because of the individualized natures of its tumors, it is possible to completely remove all visible malignant tissue. Chemotherapy and radiation are more effective treatment modalities as well. None of this is to say that lung cancer is not a serious diagnosis, because it is a deadly serious disease. It is simply to draw a clear difference between the two cancers.
There are other differences between lung cancer and mesothelioma as well. While asbestos exposure is a causative factor for both disorders, it is the only known cause of mesothelioma while lung cancer can be caused by other agents—including cigarette smoking.
Another difference between the two involves the incidence rates between the diseases. Mesothelioma is a rare disorder, affecting about three thousand people per year, while lung cancer has a diagnostic rate 65 times greater with nearly 200,000 yearly diagnoses. As people stop smoking, lung cancer incidence is expected to drop but oncologists still expect decades of tobacco-related lung cancers.
Mesothelioma and lung cancer are two very different diseases. While the most common form of mesothelioma begins in tissue very close to the lung, the very real differences in tumor structure and malignant behavior clearly identify the individual differences between these forms of cancer.
- Diffuse Pleural Mesothelioma and Asbestos Exposure in the North Western Cape Province ; by JC Wagner, CA Sleggs, Paul Marchand
- The quantitative risks of mesothelioma and lung cancer in relation to asbestos exposure; by John T. Hodgson and Andrew Darnton
Mesothelioma as it Compares to NSCLC
Pleural mesothelioma is a form of lung cancer that is almost always caused by asbestos exposure and is most commonly found in the outer lining of the lungs called the mesothelium. Most patients do not receive a diagnosis of mesothelioma until after symptoms appear, which can be 30 years or more after exposure to asbestos limiting their treatment options. The prognosis for mesothelioma patients is usually grim with no known cures, and with the average survival time varying from 4 – 18 months after diagnosis.
The prognosis for lung cancer patients, however, is good if the diagnosis is made at an early stage of the disease. Early detection of lung cancer can also offer patients with treatment options that are cures for the cancer. Whereas mesothelioma has only one primary cause-asbestos exposure, lung cancer can be caused by asbestos exposure as well as smoking, environmental hazards or genetics.
Non-small cell lung cancer is a disease in which malignant cancer cells form in the tissues of the lungs. Non-small cell lung cancer (NSCLC) is the most common type of lung cancer. It usually grows and spreads more slowly than small cell lung cancer. There are three primary types of non-small cell lung cancer:
- Squamous cell carcinoma: Cancer that begins in squamous cells is also called epidermoid carcinoma. Squamous cell carcinoma is usually found in the center of the lung by an air tube (bronchus).
- Large cell carcinoma: Cancer that can occur in any part of the lung. Large cell carcinomas tend to grow and spread faster than the other two types.
- Adenocarcinoma: Cancer that begins in the cells that line the alveoli, often found in an outer area of the lung.
The kinds of cells found in each cancer and how the cells look when viewed under a microscope determine the name for the carcinoma.
Possible early symptoms of non-small cell lung cancer include chest pain, coughing and shortness of breath.
It is important for a specialist to examine you if any of the above problems occur, to determine if your symptoms are associated with cancer. The doctor will conduct tests and procedures to diagnose the disease that you might have.
Stages of Non-Small Cell Lung Cancer:
- Stage 0 – the cancer is limited to the inner lining of the lung.
- Stage I – the cancer is small and has not yet spread to any lymph nodes.
- Stage II – the cancer has spread to some lymph nodes near the original tumor site.
- Stage III – the cancer has spread to nearby tissue or spread to lymph nodes far away from the tumor site.
- Stage IV – the cancer has spread to other organs such as the other lung, brain, or liver.
The following options are available for treatment of non-small cell lung cancer:
- Radiation therapy
- Laser therapy – Treatment that uses a laser beam (a narrow beam of intense light) to kill cancer cells.
- Photodynamic therapy (PDT) – Treatment that uses a certain type of laser light to activate a drug injected into the body to kill cancer cells.
- Watchful waiting The medical profession advocates in some rare cases to closely monitor a patients condition without giving any treatment until symptoms appear or change.
The treatment selected depends upon the stage of the cancer. A combination of treatments may be used, with research suggesting that chemotherapy or a combination of chemotherapy and radiation therapy prior to surgery is often the best treatment for patients.
Chemotherapy by itself is often used when the cancer has metastasized and is in stage IV. Chemotherapy has been shown to prolong the life and improve the quality of life in some stage IV patients.
Patients may consider taking part of clinical trials at any time during the cancer treatment. Discuss the options with your medical team to determine if there is one to fit your needs.