Pleural Mesothelioma

Pleural Mesothelioma is a cancer that commonly develops in the thin tissue lining the lungs (the pleura) and chest wall. It’s estimated that 3,000 people—mostly men over the age of 70—are diagnosed with Mesothelioma annually. Of those, approximately 80% are diagnosed with malignant Pleural Mesothelioma (MPM). Symptoms include chest pain, breathing issues, and a dry cough. Read on for everything you need to know about Pleural Mesothelioma.

What is Malignant Pleural Mesothelioma?

Malignant Pleural Mesothelioma (MPM) is the most common form of Mesothelioma—a cancer that forms tumors in the tissue lining of vital organs. A relatively rare yet aggressive form of cancer, it accounts for less than 0.3% of all cancer diagnoses in the U.S., and has a 5-year survival rate of less than 5%.

All available evidence points to the fact that Pleural Mesothelioma is caused by inhaling asbestos fibers into the lungs. Asbestos refers to a group of silicate minerals that are found regularly in the insulation of older buildings, like churches, hospitals, and homes, as well as military ships and auto parts.

After exposure, the asbestos embeds itself into the lining of the lungs, causing inflammation and scarring over time. As scarring intensifies over several decades, it can eventually develop into Mesothelioma tumors.

Types of Mesothelioma by Location

The types of mesothelioma are associated with the location in which the cancer develops as well as its cell type. The four most common types of mesothelioma by location are:

  • Pleural mesothelioma (80% of diagnoses) – Occurs in the pleura of the lungs
  • Peritoneal mesothelioma (15% of diagnoses) – Occurs in the abdominal cavity
  • Pericardial mesothelioma (<1% of diagnoses) – Occurs in the lining of the heart
  • Testicular mesothelioma (<1% of diagnoses) – Occurs in the lining of the testicles

Types of Mesothelioma by Cancer Cell

Mesothelioma can also be categorized by the type of cancer cells:

  • Epithelioid (50% of cases) – Epithelium cells line all internal surfaces, including organs and body cavities; this type is less aggressive with a better prognosis
  • Sarcomatoid (10-20% of cases) – This type of cancer can occur in several different locations; typically begins in the bones and soft, connective tissues
  • Biphasic (20-30% of cases) – These mixed mesotheliomas have both epithelioid and sarcomatoid characteristics across different areas

What are the symptoms of pleural mesothelioma?

For most people, symptoms will develop long after the initial asbestos exposure, with a latency period ranging from 20 to 71 years—this can make it difficult for those exposed during childhood or early adulthood to make a connection between their current symptoms and long-forgotten exposure. When symptoms do eventually present, they most commonly occur in the chest cavity and respiratory system. Pleural mesothelioma symptoms include:

  • Chest or lower back pain
  • Painful and dry cough
  • Shortness of breath
  • Difficulty swallowing
  • Hoarseness
  • Face and arm swelling

Unfortunately, these symptoms are mostly non-specific in that they mirror many other prominent respiratory illnesses.

What are the general symptoms of mesothelioma?

In addition to the more specific symptoms of pleural mesothelioma, patients may experience some or all of these additional symptoms of general mesothelioma:

  • Fever
  • Excessive sweating
  • Fatigue
  • Unintended weight loss
  • Blood clots
  • Loss or lack of appetite

What causes pleural mesothelioma?

The primary cause of and a major risk factor for malignant pleural mesothelioma is occupational or environmental asbestos exposure—between 70% and 80% of mesothelioma cases have had significant exposure to asbestos.

Worldwide, there has been a significant uptick of diagnoses in countries that have undergone heavy industrialization in recent decades, especially in places that have neither regulated nor banned the use of asbestos. Occupations that are most at risk for asbestos exposure and, therefore, pleural mesothelioma include:

  • Firefighters
  • Military veterans
  • Construction workers
  • Industrial workers
  • Power plant workers
  • Shipbuilders
  • Metalsmiths

How is pleural mesothelioma diagnosed?

A pleural mesothelioma diagnosis occurs many years after the initial exposure, typically ranging between 20 and 40 years, but as long as 71 years for some. Eventual diagnosis of pleural mesothelioma may be difficult because of this prolonged latency period and the non-specific nature of most symptoms.

Typically, however, the diagnosis follows three consecutive steps:

  • An initial medical evaluation, usually prompted by chest pain and breathing difficulties

A chest X-ray, which may reveal one of two standard indicators of pleural mesothelioma:

  • Fluid build-up in the lungs called pleural effusion
  • Tumors on or around the lungs

More specialized imaging scans and tissue biopsies to confirm a positive diagnosis for pleural mesothelioma, including:

  • Chest X-ray
  • Thoracic ultrasound
  • CT scan
  • Magnetic resonance imaging (MRI)
  • PET-CT scan

This is a standard progression of how a patient may eventually realize they have pleural mesothelioma—however, there are other indicators, both benign and malignant, that may spark the conversation around an eventual diagnosis.

The 4 Stages of Pleural Mesothelioma

There are four stages of pleural mesothelioma which follow the TNM staging system.

This cancer staging system was designed through a combined effort between the American Joint Committee on Cancer (AJCC) and the International Union Against Cancer (UICC) in order to determine the progression of cancerous diseases. TNM staging accounts for both the amount and the spread of cancer within the body by looking at three characteristics:

  • T – Tumor: What are the size and spread of the original tumor(s)?
  • N – Node: Has the cancer spread to nearby lymph nodes?
  • M – Metastasis: To what degree has the cancer spread to secondary sites?

To determine the extent of pleural mesothelioma, physicians will order biopsies and radiological imaging—CT, MRI, and PET scans—to measure the size and distribution of tumors. From there, oncologists use the TNM staging system to diagnose MPM, as well as develop the proper treatment plan and course of action.

The cancer staging system is complex and each unique diagnosis reflects several categories, including low- or high-grade, clinical and pathological stages, cell types, location, and beyond, but there are four broad stages of malignant pleural mesothelioma, according to the eighth edition of the TNM classification system.

StageT: TumorN: NodeM: Metastasis
IIA: Tumor localized to either the inner or outer layer of the pleura

IB: Tumor involving some other parts of the lungs and nearby muscles and tissues, including connective tissue, mediastinal fat, chest wall, and membrane surrounding the heart
No spread to the regional lymph nodes
No distant spread to other parts of the body
II
Tumor involving some other parts of the lungs and nearby tissues, including diaphragm musclesSome spread to nearby lymph nodes, especially between neck and abdomen
IIITumor involving some other parts of the lungs and nearby muscles and tissues, including connective tissue, mediastinal fat, chest wall, and membrane surrounding the heartIncreased spread to nearby lymph nodes, including the supraclavicular nodes near the neck, which are most worrisome
IVTumor has spread throughout the initial area—the lungs
Distant spread to other parts of the body
TNM Staging System

What are the treatment options for pleural mesothelioma?

The most common treatment for pleural mesothelioma is chemotherapy. However, multimodal therapy—the combination of various treatments—is a promising path for those diagnosed early. Multimodal therapy offers relief and improves chances of survival by bringing together some or all of the following treatments:

  • Heated Intraperitoneal Chemotherapy (HIPEC), which targets cancer cells in the abdominal cavity.
  • Cytoreductive surgery, which removes cancerous growths in the early stages, before excessive spreading.
  • Palliative care to ease symptoms and improve quality of life.
  • Emerging treatments like immunotherapy, gene therapy, radiation therapy, and more.

Despite the accelerated timeline of this aggressive form of pleural cancer, there are certain promising treatment options—both traditional and emerging—that can prolong patients’ lives, especially when diagnosed during the early stages.

What are the emerging treatments for pleural mesothelioma?

As doctors and scientists learn more about this misunderstood and aggressive disease, they are able to introduce new viable treatment courses. All or most of these options require further research, but have shown some encouraging results thus far:

  • Immunotherapy – This course of treatment uses the body’s own immune system as a tool in fighting off cancer and tumor growth. It’s either passive—removing, isolating, activating, then re-injecting certain cells—or active—using an antigen (a foreign substance or toxin) to trigger an aggressive immune response.
  • Radiation therapy – This therapeutic treatment uses beams of radiation to target and kill cancer cells. Radiation therapy can be used to prevent spreading, treat pain or potential cavity compression, and in high doses, eradicate or control tumor growth, thereby increasing survival rates. Trials over the past 10 years have demonstrated the safety and efficacy of radical high-dose radiation, though further studies are required.
  • Photodynamic therapy – Another type of radiation therapy, this non-ionizing treatment uses a photosynthesizer (a drug) and light energy to destroy both cancerous and precancerous cells. Several trials have found varying levels of success with photodynamic therapy, specifically with prolonging survival and decreasing tumor regrowth.
  • Gene therapy – This new treatment path involves adding genes to the existing cancer cells, in order to make them easier to kill. One promising variation includes modifying and injecting viruses into the pleura, which then infect the cancerous cells.
  • Alternative options – Medical marijuana, acupuncture therapy, and dietary supplements can all provide relief and complementary solutions to traditional treatment methods.

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What clinical trials are underway for pleural mesothelioma?

As with any rare disease, scientists and medical professionals are constantly seeking out and testing new treatments. There are many promising options at various stages of development.

Phase I Trials:

  • Study of a Targeted Cancer Vaccine (Galinpepimut-S) Combined with Nivolumab Immunotherapy in Patients with Persistent Pleural Mesothelioma
  • Study of CAR T-Cell Immunotherapy for Pleural Mesothelioma

Phase I/II Trials:

Phase II/III Trials:

  • Study of Chemotherapy with or without ADI-PEG 20 in Patients with Malignant Pleural Mesothelioma

What’s the typical prognosis for pleural mesothelioma?

As with any diagnosis, each person’s individual medical journey will be unique. However, pleural mesothelioma is a rare and poorly-understood condition that develops on an accelerated timeline. Without a definitive cure, the prognosis is poor for many patients—with a median survival of 18.4 months.

Years since diagnosis
Survival percentage
1
73.1%
322.9%
512%
104.7%
  • Age – The median survival rate was much longer for 18-44-year-olds (59 months) than for those 75 or older (only 10 months).
  • Sex – The survival rate is much higher for females as compared to males, perhaps in part because of the increased rates of estrogen and higher expression of the estrogen beta receptor.
  • Stage – Those at an earlier stage have a better overall survival rate, with a median time of 21 months for stage I cases and 12 months for stage IV cases.
  • Histology – Cases with epithelioid, rather than biphasic or sarcomatoid, cells have a better survival rate—a hazard ratio of 0.48, compared to 1.0 and 0.97, respectively.
  • Treatment – One study showed that chemotherapy was a favorable prognostic factor, while another claimed it was the only treatment method that showed improved survival rates.

For untreated cases, the median survival rate is between six and nine months. With the right treatment, or combination of treatments, many patients live much longer. Despite the grim overall prognosis for pleural mesothelioma, the current and ongoing advancements in the field have left people feeling somewhat optimistic about future prognosis.