What is Mesothelomia?
Mesothelomia cancer is a cancer developed at the expanse of any serous cavity:
•Pleura (lining of the lungs)
•Peritoneum (abdominal cavity)
•Pericardium (heart envelope)
A ratio of 10:1 is observed for the occurrence of the pleural kind versus the other kinds of mesothelomia. Therefore the most common mesothelomia is the pleural (lung) mesothelomia, which is presented here.
The incidence of malignant pleural mesothelomia increases with age, with a maximum frequency being observed for ages 75 to 79. The annual incidence steadily increases and is estimated to be 4.7% in men and 6.8% in women. In industrialized countries, 250 000 new cases are expected in the next 35 years. Incidence is expected to double by the year 2025, due to a professional or para-professional exposure to asbestos.
What is Pleural Mesothelomia?
The lungs and the interior of the chest walls are covered with a thin membrane called the pleura. These two membranes are separated by a small amount of liquid (the pleural fluid) that facilitates changes in volume of the lungs during respiration.
In general, the mesothelium is a tissue that consists of a single layer of epithelial cells lining the surface and covers the interior of serous tunics of the body such as the peritoneum, pericardium or pleura.
The different types of tumors
Different types of pleural cells can transform into malignant cells and induce pleuro-pneumonic mesothelioma that comes in 3 histological types:
•The epithelial type (Epithelioid mesothelioma) is the most common with 70% of cases.
•The sarcomatous type (Sarcomatoid mesothelioma) occurs in 10% of cases.
•A mixed or biphasic variant combines the two previous forms (20% of cases).
Risk factors
Exposure to asbestos
Only asbestos exposure provides a level of absolute proof of causation in pleural mesothelioma - indeed it is sometimes called asbestos cancer. A history of asbestos exposure exists in almost all cases.
Other risk factors
Apart from asbestos, studies suggest that the simian virus (SV40) may act as a cofactor in the development of mesothelioma, as well as radiation and ceramic fibers.
Symptoms felt by the patient
Non-symptomatic cases are observed in cases of slow tumor development, but a typical case would be that of a 60 years old men, exposed to asbestos, with pleurisy (fluid in the lungs). In 10% of cases, mesothelioma is suspected after a painful hemi-thoracic retraction revealing a circumferential pleural thickening. Other circumstances of discovery: an accidental radiological diagnosis, or the existence of a parietal swelling in a pleural punction hole.
An alteration of the general condition is frequent, involving anorexia / weight loss, fever peaks, abundant sweats. Chest pain comes early and is permanent, with bottom-up irradiation and rapidly increasing in intensity.
Dyspnea (difficulty breathing) is mostly linked to the presence of fluid in the lungs.
The nodal areas are not affected.
Diagnosis
The purpose of the diagnostic is to highlight the existence of mesothelomia: by finding the tumor and by ensuring its cancerous nature. There are several exams that may be useful for this and the choice of some over others depends on the patient's condition and on the information the doctor needs to gather to establish the diagnostic. It is rarely necessary to practice all the examinations listed below.
Chest X-Ray
A chest X-ray is the first para-clinical examination performed for all chest-related symptoms. It shows 75% of cases of mesothelioma at diagnosis. Any abnormality of the standard X-ray will lead to a chest scan. But the presence of an abundant pleural effusion is enough evidence to lead directly to an exploratory puncture.
The scanner
It is a radiography technique using a computer to generate 3D images of the organs in the body. This is painless, but it takes a little longer than an ordinary X-ray (between 10 to 30 minutes). A contrast product is used to better visualize certain organs: this product, opaque to X-rays, can be injected into a vein or swallowed. They contain iodine, it is therefore important to tell any history of allergy to iodine. An allergy does not prevent the scan, but an anti-allergy drug must then be taken. It is also important to mention if you have other allergies, asthma, a renal disease, diabetes or if you took medication (including aspirin).
There is no need to be fasting prior to the scan. During the scan, the surface on which the patient is installed will move steadily throughout the exploration. At any moment, the patient can communicate with the medical team through a microphone embedded in the device. Feel free to report what you feel. Duration of the exam: 20 to 40 minutes.
Puncture
A thin needle is introduced in the space between the two pleura to recover the pleural fluid for examination. Its efficiency in detecting a mesothelomia is around 20%, so it does not contribute a lot in a diagnosis specifically aimed at uncovering mesothelomia. It also serves to completely evacuate the pleural fluid in cases of shortness of breath or to facilitate the visualization of scan images.
Thoracoscopy
Thoracoscopy is the exam of choice in the diagnosis of pleural mesothelioma, with an efficiency reaching 98% in reference centers. The inspection of the pleural cavity is exhaustive and pleural biopsies carried out this way have all the qualities required to confirm a histological diagnosis of pleural mesothelioma: many samples of sufficient size and covering all pleural sheets.
It is a small operation that consists in the introduction of a small "telescope" into the abdomen by practicing a small incision of less than an inch in the chest wall. The doctor can then see the two pleura, and also perform biopsies. This exam is done under general anesthesia and requires a brief hospital stay.
Biopsy
It involves taking a piece of suspect tissue for examination under a microscope. The analysis, performed by a specialist (anatomical pathologist), allows to know the nature of the tumor and to confirm the diagnosis. There are different ways to obtain that biopsy: by percutaneous means (through the skin) during a scan, by a surgery following a thoracoscopy or during a thoracotomy (if it is programmed immediately).
It is this analysis of the cells which makes it possible to positively diagnose a pleural mesothelioma.
Assessment of the Extension of the Cancer
The purpose of the assessment is to determine the extent of the cancer and to propose the most adapted treatment to the patient. The primary treatment of pleural mesothelomia is surgery. The extension assessment will determine whether a surgery is possible and appropriate and define for each patient the best sequence of treatment.
The degree of extension of the tumor is evaluated based on the results of the scan and thoracoscopy.
Further reading
Understanding Cancer: A Patient's Guide to Diagnosis, Prognosis, and Treatment
Amazon Price: $23.30
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100 Questions & Answers About Mesothelioma, Second Edition
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Living With Cancer: A Practical Guide
Amazon Price: $44.92
List Price: $44.95
Dying of Cancer: The Final Year of Life
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They Said Months. I Chose Years! A Mesothelioma Survivor's Story
Amazon Price: $15.00
List Price: $19.95
Treatment
The ultimate goal of the various treatments proposed for mesothelomia is the elimination of a bulk of the disease through surgery, knowing that there is a risk that there will remain microscopic residual spots. Adjuvant therapy may be done jointly with surgery; it seeks to eliminate residual cancer cells. The most common adjuvant therapies are radiation therapy, chemotherapy and new targeted therapies.
Surgical treatment
It is the main treatment. It is an extremely complex and specialized surgery. Results have greatly improved during the last ten years. Two surgical techniques are used: the extra pleural pleuro-pneumonectomy and the pleurectomy.
Radiotherapy
Radiotherapy is a local treatment: it acts on the area affected by cancer. It uses rays of different energies to destroy cancer cells. But healthy cells of the irradiated area are also affected, explaining the side effects of radiation. The healthy cells, with their higher resistance and their ability to recover will be able to regenerate themselves, unlike the malignant cells.
In the case of mesothelioma, its use is limited by the presence of radiosensitive organs in its immediate vicinity. But its association with chemotherapy can reduce the volume of the tumor and allow surgery which could not be envisaged before. It is also used as an analgesic (anti-pain) treatment and as a prophylactic treatment of drainage or thoracoscopy holes.
The neoadjuvant and adjuvant treatments
These treatments are performed in addition to surgery.
Neoadjuvant treatments are performed before the surgery: chemotherapy with or without targeted therapies.
Adjuvant treatments are performed after the surgery, and consist of radiotherapy, chemotherapy or the combination of both.
Immunotherapy
It has been observed among patients with mesothelioma, or simply exposed to asbestos, that there is an alteration of the immune response. These observations suggest that the patient's immune system plays an important role in the control of the growth of mesothelioma. Indeed, the immune system is constantly looking for abnormal cells to destroy. Unfortunately, this defence system is not always efficient enough, and cancer may develop. Therefore, in some cases, treatments capable of stimulating the immune system are used, as interferon alpha and interleukin 2. But these treatments have significant side effects. They are more often prescribed in younger patients in relatively good health condition.
Chemotherapy
It is a therapy that involves the diffusion of drugs to destroy cancer cells throughout the body. The manner in which drugs are administered (choice of drug, rate, dose, ...) is called the chemotherapy protocol.
For mesothelioma, clinical studies have shown interest to combine Cisplatine to Pemetrexed (Alimta). Other products are used alone or in associations:
Carboplatin (Paraplatine)
Gemcitabine (Gemzar)
Doxorubicin (Adriamycin)
Mitomycin
Vinorelbine (Navelbine)
A short monitoring at the hospital is sometimes required for the first treatment. Most chemotherapy drugs are administered by intra-venous infusion and require the introduction of a catheter to be injected safely. Before each treatment, the doctor checks the health of the patient and the results of his blood tests.
