Peritoneal Mesothelioma

 

A peritoneal mesothelioma is a rare form of cancer that affects peritoneum (a fine lining that surrounds the tissues and organs inside the abdomen).

The disease is caused after long time exposure to asbestos (inhalation or ingestion). In the late 19th century, asbestos was considered as an ideal construction material. It’s a cheap material, reductant to fire, with high electrical resistance, and has excellent insulation properties. Not before 1920’s its detrimental effects to human health were spotted. It took approximately 70 years before it became clear how dangerous it is. In the 1990’s 60 countries worldwide banned the use of asbestos in whole or in part. The consequences of long-term exposure to asbestos are visible even today. Due to occupational exposure at construction sites, the incidence is higher among males than among females.

Peritoneal mesothelioma is just one of three forms of asbestos-related cancers.  Beside peritoneal (the second most common), pleural mesothelioma (the most common type), and pericardial mesothelioma (the rarest type) are described. Each year, in the US fewer than 3000 people are diagnosed with mesothelioma, of which fewer than 500 are diagnosed with peritoneal mesothelioma.

In the past 20 years, thanks to treatment improvements, prognosis (life expectancy and survival rates) improved dramatically. Unfortunately, mesothelioma remains to be one of the malignant diseases with the poorest prognosis.

Symptoms

The reason why peritoneal mesothelioma has such poor prognosis lies in the fact that its asymptomatic until the terminal stages of disease, when internal organs of the abdomen are already infiltrated. Actually, almost all symptoms are explained by mechanical obstruction the cancer makes as it infiltrates abdominal cavity. The fact that most peritoneal mesothelioma patients are 65+ years old makes the diagnosis harder, since the symptoms they complain of often lead doctors reasoning towards benign gastrointestinal conditions that come with age.

–    Anorexia and weight loss

As cancer grows, it needs more and more nutrients to sustain itself. It literally depletes body’s energy deposits which leads to weight loss. The weight loss greater than 10% of body weight in the last 6 months (without intentional dieting) requires further medical examination and explanation.

–    Fever

As cancer grows, its cells sometimes produce substances that cause fever while in other cases the microscopic necrosis inside affected tissues triggers inflammatory response and fever. Typically, the body temperature is mildly increased and remains like that for days, even weeks.

–    Fatigue

As cancer drains nutrients from the body, patients feel exhausted all the time without an explanation. As we mentioned above, quite often this sign is misinterpreted as a “symptom of old age” rather than a symptom of a disease.

–    Abdominal/ stomach pain

As cancer infiltrates abdominal wall, it may compromise the integrity of abdominal organs, or cause painful sensations due to “pulling” of the tissue.

–    Ascites/ swelling

Ascites and generalized swelling are symptoms of liver failure. The failure is a consequence of, not only physical damage that liver takes as cancer grows but of functional abnormalities as well. These abnormalities are the result of nutritional depletion.

–    Changes in the bowel and bladder function, unusual bleeding, digestion problems, palpable masses in the abdomen, etc. 

Those symptoms suggest that some kind of infiltration and expansion may be happening. Although they are not specific for mesothelioma, they are a reason for thorough medical examination.

–    Is there a symptom that’s highly specific for parietal mesothelioma?

No, parietal mesothelioma is a diagnosis primarily made with the help of imaging techniques and laboratory findings. Quite often, the disease is discovered accidentally (while performing a laparoscopic removal of the gallbladder, for example).

Treatment options

Surgery

Surgical removal (also known as debulking or cytoreduction) of the cancer is performed only in cases of early staged disease (stages 1 and 2). Sometimes, terminal patients undergo a palliative surgery if that’s the only way to ease the symptoms. Since the tumor has diffuse growth, it’s impossible to remove it entirely this way. The goal is to remove as much of it as possible. Surgery is just a complementary method of treatment. Patients almost always undergo other treatment modalities after surgery (chemotherapy, HIPEC, radiation).

Chemotherapy

Chemotherapy is a systemic treatment with highly cytotoxic drugs. Typically, the drugs are administered intravenously. The therapy (especially having in mind that most of the patients are 65+ years old), have serious adverse effects. In case of peritoneal mesothelioma, chemotherapy is a lesser of to evils.

HIPEC

In the last two decades, a new approach in delivering chemotherapy in the treatment of abdominal cancer emerged. It’s known as Hyperthermic Intraperitoneal Chemotherapy. The approach is not exclusively reserved for peritoneal mesothelioma. Actually, at first, it was designed to fight off ovarian, colon and other (common) abdominal cancers. The principle is simple- the abdomen is irrigated with a heated mixture of cytotoxic drugs. Increased temperature speeds up the metabolism of cancer cells, making them even more vulnerable to chemotherapy. At the same time, the drugs are administered locally (into the abdominal cavity), which significantly reduces the amount of drug that reaches bloodstream (and allows doctors to use more aggressive cytostatic drugs than routinely used cisplatin). The treatment is performed only in a few highly specialized health facilities in the world. The results are encouraging- it’s more effective than classical surgery+ chemotherapy treatment.

According to American Society of Clinical Oncology, two-thirds of patients who received this treatment survived 3.4 years on average, which is significantly longer than survival time of patients who received a standard treatment for peritoneal mesothelioma.

Radiation

Radiation therapy is used as palliative treatment, or adjuvant therapy after the surgery or as a seeding prevention (before, after or independently of surgical treatment).

Palliative radiation therapy

In some cases, the tumor mass is the cause of pain, discomfort, and suffering in the terminally ill patient. In situations like that, if overall health condition of a patient allows, radiation therapy is delivered to reduce the size of a tumor, easing the symptoms that way.

Adjuvant therapy after surgery

As mentioned above, due to the characteristics of peritoneal mesothelioma growth, surgery offers just a limited success in tumor reduction. The only way to destroy small (sometimes invisible to the naked eye) tumor particles is to deliver radiation therapy. With the technology available, we can deliver it quite accurately, minimizing the adverse effects of such treatment.

Prognosis

The prognosis depends on a number of factors. Staging of a tumor is probably the most important (the degree of infiltration, has it spread into the regional or distant lymph nodes and tissues, etc.). Lower stages correlate with better prognosis (but this isn’t a rule, sometimes patients with higher stage tumor outlive those with stage 1 pleural mesothelioma, for example). The tumor cells type plays a major role as well- epitheloid type has a better prognosis than biphasic and sarcomatoid. Survival time in women is longer than in men. Younger patients survival time is significantly longer than in 65+ years old population.

The median survival period for peritoneal mesothelioma is 1 year. The longest documented survival time was 19 years.