Staging systems were employed in order to determine the severity and evolution of cancer, focusing on various factors such as the location, size, and grade of the tumor, the type of cells which are contained by the malignant growth, as well as its extent. There are multiple staging systems for assessing pleural mesothelioma, including the Butchart System, the TNM System, and the Brigham System. The first, however, is the most commonly used, as well as the oldest.

Due to the prevalence of the pleural type, which accounts for nearly 80% of all diagnosed mesothelioma cases, the Butchart Staging System is solely available for this disease. Nevertheless, pericardial and peritoneal mesothelioma can also be accurately evaluated by an experienced specialist, even in the absence of a proper staging system.

The evolution of pleural mesothelioma is divided into four stages according to all three previously mentioned systems, the severity of the condition increasing with the number of each stage. Thus, patients diagnosed with stage I mesothelioma will experience none or very few symptoms, while stage IV mesothelioma is associated with distressing and intense symptoms, as well as with limited treatment options. Detecting the disease in its incipient phases is, therefore, crucial for a favorable prognosis and a prolonged life expectancy.

The Butchart Staging System

The oldest cancer staging system was suggested by Eric Butchart in 1976. It focuses primarily on the location of the tumor and can also determine whether the malignant growth is eligible for surgery. This staging system is also the most commonly employed nowadays. However, it does not provide additional information such as the size of the tumor or the number of malignant cells present within the body. According to the Butchart System, the four stages of pleural mesothelioma are as follows:

Stage 1: The malignant tumor is restricted to the outer lining of one lung (right or left pleura) and metastases are not present. The adjacent region of the diaphragm may also be affected. The first phase of pleural mesothelioma can also be divided into two more specific stages, 1A and 1B. While in stage 1A cancer is located exclusively on the outer surface of the lung (parietal), stage 1B entails its spreading to the inside of the organ (visceral). During stage 1, cancerous cells can thus be found in one or more of the following chest regions:

• the outer lining of one lung
• the diaphragm
• the lining of the chest wall
• the inner layer of the pleura

It is worthy of note that patients diagnosed with stage 1 pleural mesothelioma have the widest range of treatment options available, including surgery, as malignant cells are confined to a limited region of the body. Additionally, treatments are generally very effective at this point and the chances of mesothelioma recurring are also significantly reduced. A multimodal treatment approach combining surgery, radiotherapy, and chemotherapy has been demonstrated to represent the most efficient approach for stage 1 pleural mesothelioma. Prognosis is relatively positive as well, with the majority of patients surviving for over 3 years with prompt treatment.

Stage 2: Cancer has affected the chest wall and may have also metastasized to the outer lining of the other lung, esophagus, heart or lymph nodes in the chest. Although the tumor is still restricted to the chest region, stage 2 is deemed the first advanced phase of pleural mesothelioma due to the presence of one or multiple metastases. Thus, the following organs and areas might be reached by malignant cells during the second stage:

• the lymphatic system
• the other lung’s pleura
• the diaphragm
• the esophagus
• the outer lining of the heart

The survival rate of patients suffering from stage 2 pleural mesothelioma can be considerably extended by undergoing appropriate treatment. The HIPEC (Hyperthermic Intraperitoneal Chemotherapy) treatment approach, which combines surgery with heated chemotherapy, has proved to be particularly effective for eliminating malignant cells when this phase of cancer is ongoing. Nevertheless, the patient’s overall health needs to be satisfactory in order to successfully undergo this treatment, as it is quite aggressive. High doses of radiation may also be beneficial at this point, according to the Butchart System.

Prognosis is still relatively good for stage 2 pleural mesothelioma if the patient receives appropriate treatment soon after the diagnosis. Approximately 30% of all stage 2 patients who had surgery survive for over 3 years, while 53% of those who opted for HIPEC treatment will live for at least five years.

Stage 3: The tumor has spread to the diaphragm or peritoneum (the abdominal lining) and has also extensively affected the lymphatic system outside of the chest cavity. Consequently, metastases to one or multiple of the following regions typically accompany stage 3 pleural mesothelioma:

• the soft tissue in the chest wall
• the outer lining of the heart
• the peritoneum
• the fat tissue between the lugs

Surgical treatment is rarely recommended for patients diagnosed with stage 3 pleural mesothelioma, as cancer has severely affected the chest and abdominal regions and this option would thereby entail tremendous risks for their health. However, palliative care is available in order to alleviate the distressing symptoms which are generally associated with this phase. It includes:

• radiation therapy
• chemotherapy
• the draining of excessive fluid from the affected area (thoracentesis for the chest cavity, pericardiocentesis for the heart region and paracentesis for the abdominal cavity)

It is highly important to mention that palliative treatment cannot cure cancer, as the disease is unfortunately too advanced. The purpose of palliative care is to relieve the pain and other symptoms occurring in the third stage of pleural mesothelioma. Prognosis will primarily depend on how responsive to treatment the malignant tumors are. The average life expectancy for stage 3 is approximately one year. Nevertheless, nearly 30% of patients who are eligible for HIPEC treatment (surgery and heated chemotherapy) will survive for up to five years.

Stage 4: Pleural mesothelioma in stage 4 is accompanied by very severe symptoms and cancer which entered this advanced phase is often terminal. Malignant cells have infiltrated the bloodstream, leading to distant metastases. Thus, the following organs and regions might be affected as well:

• the lymphatic system
• the outer lining of the heart
• the brain
• the spine
• the prostate
• the liver
• the bones
• the thyroid gland

Palliative treatments are exclusively available for stage 4 pleural mesothelioma, as cancer is very aggressive and unresponsive to curative surgery. Moreover, surgical treatment would imply extremely serious health risks at this point and is therefore strictly not recommended. Palliative treatment options include:

• radiotherapy
• chemotherapy
• oxygen therapy
• the draining of excessive fluid from the chest, heart or abdominal region

Prognosis for stage 4 pleural mesothelioma is generally poor, with an average life expectancy of approximately one year. However, patients who are young, in relatively good health, diagnosed with malignant epithelial tumors and whose blood has not been contaminated with cancerous cells can often exceed this period of time and survive longer.

The TNM Staging System

The TNM Staging System was developed by Pierre Denoix between 1943 and 1952. It focuses on three variables to assess and monitor the evolution of cancer:

• tumor (T): it describes the particularities of the tumor (location, size etc.)
• lymph nodes (N): it states whether the lymphatic system has been affected by malignant cells
• metastasis (M): it determines whether cancer has spread to adjacent or distant organs and regions of the body

This staging system is only used to evaluate solid tumors and cannot be employed in the assessment of diffused cancers such as leukemia, diffuse ovarian cancer or diffuse lymphoma. It also involves four stages of cancer whose number increases with the severity of the disease. For pleural mesothelioma, the TNM stages are the following:

Stage 1: The tumor developed on the outer lining of the right or left lung and may have metastasized to adjacent organs and regions such as the pericardium, the inside of the lung or the diaphragm. Malignant cells have not infiltrated the lymphatic system.

Stage 2: Cancer has spread to the lymph nodes on the same side of the chest cavity where the primary tumor occurred. Additional metastases to the outer lining of the heart, diaphragm or the inside of the lung may also be present.

Stage 3: The malignant cells have reached several of the following organs and areas: heart, esophagus, chest wall, ribs or adjacent muscles in the chest cavity, producing multiple metastases. The lymph nodes may or may not be affected.

Stage 4: Pleural mesothelioma has reached the other half of the chest cavity, affecting the organs and tissues in this region, as well as the lymph nodes. Distant metastases to one or multiple organs in the abdominal region may also occur.

The Brigham Staging System

This staging system was designed by Dr. David Sugarbaker at the Brigham and Women’s Hospital in Boston in 1993. It is based on his clinical experience with 52 patients and was improved in 1998. In addition to providing information regarding the particularities of the tumor, the condition of lymph nodes and the existent metastases, the Brigham System can also assess whether the malignant growth is resectable (eligible for removal via surgery).

The Brigham System also uses four stages to monitor the evolution of cancer. For stage 1 and stage 2 pleural mesothelioma, surgery is generally a viable treatment option and can generally be undergone without health complications. The severity and complexity of the last two stages, however, do not allow the performance of surgical intervention, as pleural mesothelioma is too advanced and the health of the patient would be in great danger. Therefore, according to this system, the malignant tumor is only resectable during the first two stages, while surgery is not recommended as a treatment for pleural mesothelioma during the last stages of the disease.

Despite the accuracy and reliability of the staging systems presented above, it is essential to remember that every patient diagnosed with mesothelioma is unique and reacts differently to treatment, depending on a wide variety of factors such as age, overall health and the existence of other conditions or diseases within their body. Thus, regardless of how advanced cancer might be, the current stage of the disease should not discourage one from seeking appropriate treatment.

Alternative approaches, as well as experimental treatment options which can be undergone in clinical trials, are also available and can significantly improve the prognosis of mesothelioma when used in conjunction with standard treatment. While staging systems are fundamental to properly diagnose and monitor pleural mesothelioma, the ongoing phase of your conditions does not always reflect your chances of survival and cannot predict how responsive to treatment cancer will be.