Although pleural mesothelioma and lung cancer are separate cancers, both can result from asbestos exposure. While the two conditions primarily affect the lungs, there are vital differences between them.
Though malignant pleural mesothelioma affects the lungs, it is not considered a type of lung cancer, because it forms in the lining around the lungs rather than in the lung tissue.
These cancers originate in different locations, yet cause similar symptoms such as shortness of breath, chest pain, fatigue and weight loss. Symptoms tend to arise late in the development of both cancers.
Though medical teams use surgery, chemotherapy and radiation therapy to treat both conditions, the treatment plans differ, and what works for one cancer will not work for the other. Photodynamic therapy has been used on both, but it is more commonly used on lung cancer and is only experimental for pleural mesothelioma.
|Lung Cancer||Pleural Mesothelioma|
|Forms in lung tissue||Forms in the lining around the lungs|
|Common condition with more than 220,000 Americans diagnosed per year||Very rare with about 3,000 Americans diagnosed annually|
|Caused by smoking, air pollution and asbestos exposure||Caused primarily by asbestos exposure|
|Mainstream treatment options are surgery, chemotherapy and radiation||Also treated with surgery, chemotherapy and radiation but targeted differently|
|Tumors are well-defined masses that are easier to target for treatment||Tumors are thinly spread over healthy tissue, making them more difficult to target|
|5-year survival rate: Almost 18 percent||5-year survival rate: Less than 10 percent|
When microscopic asbestos fibers are inhaled, they can become lodged in lung tissue or the pleura, which is the lining of the lungs, and the mineral fibers can cause cancer in both locations. Asbestos lodged in lung tissue causes lung cancer (LC), while asbestos lodged in the pleural lining causes pleural mesothelioma (PM).
All forms of asbestos, including amphibole and serpentine types, are known to cause lung cancer and pleural mesothelioma.
Amphibole forms of asbestos (including amosite, crocidolite, tremolite and anthophyllite) are more carcinogenic than serpentine asbestos (chrysotile).
Regardless of the type of asbestos someone is exposed to, significantly less asbestos exposure is required to cause pleural mesothelioma than lung cancer.
In either case, it usually takes many years for asbestos exposure to cause cancer to develop. The average latency period for pleural mesothelioma is 10 to 50 years, while lung cancer’s latency period is shorter, at 10 to 20 years.
Asbestos exposure alone can cause both PM and LC, and smoking alone can cause lung cancer. However, smoking alone cannot cause pleural mesothelioma, and smoking doesn't increase the risk of PM in those exposed to asbestos.
Studies have proven that the combination of smoking and asbestos exposure can increase the risk of lung cancer fiftyfold.
Conversely, other research has proven that smoking does not affect the risk of developing pleural mesothelioma at all.
Because the toxic combination of smoking and asbestos exposure significantly increases the risk of LC but not PM, there are about twice as many cases of asbestos-related lung cancer in comparison to pleural mesothelioma.
It’s also worth noting that lung cancer risk decreases after smoking cessation, but the risk of pleural mesothelioma only increases with age. The body cannot recover from asbestos exposure the way it can from cigarette smoking — because asbestos fibers can become trapped in bodily tissues indefinitely, ongoing damage can carry on for decades. The risk of LC may decrease with time and smoking cessation, but the risk of PM only continues to increase.
Doctors use similar diagnostic tools to identify these cancers, and the expertise of a specialist is required to differentiate PM from LC.
X-ray: This is often the first test to show tumor growth around the lungs.
CT or PET scan: Advanced imaging tests provide more detailed pictures of the inside of the chest and lungs.
Biopsy: Collecting samples of cancerous tissue with a long needle or a minor surgery is essential to accurately diagnose the cancer.
Sputum cytology test: If doctors suspect lung cancer, they can examine phlegm expelled by the patient.
Bronchoscopy: Another common procedure for diagnosing lung cancer involves inserting a tube down the patient’s throat into the large airways to check for abnormal growths.
The most accurate and definitive method is to have a pathologist examine biopsy samples to decipher which cancer is present from a cellular level.
However, if the patient has a history of possible asbestos exposure, they should seek the opinion of a specialist in asbestos-related diseases. Pleural mesothelioma is sometimes misdiagnosed as lung cancer, because at the microscopic level, it can resemble adenocarcinoma, the most common type of non-small cell lung cancer. It can also resemble sarcoma, a cancer that forms in soft tissue.
The early staging of both cancers is similar, but it differs in the latter stages as the cancer spreads.
The tumors are localized, remaining where they originally developed.
The tumors are locally advanced, meaning they’ve grown and spread to nearby organs and lymph nodes.
Lung cancer spreads throughout both lungs and to other parts of the body such as the brain, bones, liver and adrenal glands. Mesothelioma less frequently spreads to distant locations, but may spread throughout both lungs or to the bones or brain.
Survival rates for these cancers are similar for the first year after diagnosis, but thereafter, lung cancer patients have better chances for long-term survival. Less than 10 percent of pleural mesothelioma patients live for 5 years, while nearly 18 percent of people with lung cancer live that long.
Common treatment options for PM and LC are the same as for other cancers: Surgery, chemotherapy and radiation therapy. However, medical professionals treat PM and LC with distinct types of surgeries, chemotherapy drugs and radiation techniques because the two cancers form differently.
Lung cancer tumors typically grow as individual masses, which makes them easier to surgically remove and target with chemotherapy and radiation.
Mesothelioma develops as many small interconnected tumors that eventually blend the boundaries between healthy and cancerous tissue, making it much more difficult to target.
Different combinations of conventional treatments, known as multimodal therapies, are effective for each cancer, depending as well on the stage of the tumor and the overall health of the patient.
Surgeries for lung cancer will attempt to remove either a portion of the affected lung, a lobe or the whole lung. Pleural mesothelioma surgeries may involve the removal of the pleural lining, a portion of the lung or the entire affected lung. Certain palliative surgeries, such as a pleurodesis, can provide pain relief in advanced cases of either cancer.
Only certain chemotherapy drugs are effective in treating PM and LC, and even then, the dose will depend on which cancer a patient has and the stage of the tumor.
Cisplatin and pemetrexed are the most common chemotherapeutic agents used for PM, while docetaxel, vinorelbine and paclitaxel are common for treating LC. Chemotherapy drugs used for both cancers include cisplatin, carboplatin, pemetrexed and gemcitabine.
Radiation therapy is difficult to administer to either cancer because of the proximity of the lungs to vital organs such as the heart and spinal cord. When administered alone, radiation aims to ease pain in PM and LC patients, but it cannot cure these cancers.
When combined with other treatments, especially following aggressive surgery, radiation therapy can reduce local tumor recurrence in PM and LC. For PM patients, radiation has also been used along tracts created by biopsies, chest tubes and surgical incisions to prevent tumor seeding, or local metastasis along the incision. Tumor seeding is rare in lung cancer.
Specialists have used photodynamic therapy to treat PM and LC, but it is more commonly administered to lung cancer patients. Researchers have used other novel treatments, such as immunotherapy and gene therapy, for both cancers with limited success so far.
Complementary and alternative medicine is available for both cancers and can ease symptoms as well as reduce side effects of conventional treatments.
The prognosis for PM and LC is similar for the first year after diagnosis, but the survival rate for LC is higher in the long-term.
|Survival Rate||Lung Cancer||Pleural Mesothelioma|
Diagnosing the cancers early significantly improves survival rates.
When lung cancer is diagnosed while the tumor is localized, the five-year survival rate is approximately 53 percent. In one pleural mesothelioma study conducted at Brigham and Women’s Hospital, 46 percent of patients diagnosed in stage 1 survived beyond five years. These patients all had an epithelial cell type and successful surgeries that cleared nearly all tumor cells.
Despite their similarities, pleural mesothelioma and lung cancer are separate conditions that require different treatment plans to extend survival. Patients with either cancer should work with a specialist who can offer expertise in the latest available treatments.
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