Written By: Camryn Keeble

Peritoneal Mesothelioma Stages

Knowing and understanding peritoneal mesothelioma stages is a crucial part of diagnosing this cancer. Learning the stage of your peritoneal mesothelioma will offer insight into your prognosis and potential treatment options. Peritoneal mesothelioma is staged differently than most cancers, as peritoneal cancer specialists use the Peritoneal Cancer Index (PCI) to determine the severity of the cancer.

Karen Ritter, RN BSN

Medically Reviewed By

Karen Ritter, RN BSN

Registered Nurse

Karen Ritter, RN BSN

Medically Reviewed By

Karen Ritter, RN BSN

Registered Nurse


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Important Facts About Peritoneal Mesothelioma Stages

  • Knowing the stage of a peritoneal mesothelioma diagnosis is crucial to determining a patient’s treatment plan.
  • Patients diagnosed in early stages will have a better chance of treating their peritoneal mesothelioma, while late-stage patients have a lower chance of succeeding with aggressive treatments.
  • Specialists score peritoneal mesothelioma using the Peritoneal Cancer Index (PCI) and then may assign a stage.

How Many Stages Does Peritoneal Mesothelioma Have?

Peritoneal mesothelioma uses a different cancer staging system. It calculates a score for the patient’s cancer based on the spread of tumors in the abdominal cavity. Specialists may wish to translate the PCI score into a specific stage, such as stage 1, stage 2, stage 3 or stage 4.

Stage 1 is the least severe, offers the best life expectancy, and allows the patient to be eligible for more peritoneal mesothelioma treatment options. Stage 4 is the most advanced stage, has the most challenging symptoms and limited treatment options.

Peritoneal mesothelioma is a rare cancer that forms in the peritoneum, the thin lining that covers the inside of the abdominal cavity. For patients with early stage (stage 1 or stage 2) peritoneal mesothelioma, their cancer is most likely contained to the peritoneum and has not spread to other organs. Late stage (stage 3 or stage 4) peritoneal mesothelioma patients often experience more severe symptoms as their cancer has likely spread and grown throughout the abdominal cavity and to nearby organs. 

Most often, peritoneal mesothelioma is diagnosed in stages 2, 3, or 4. Stage 1 is rarely diagnosed due to vague or minor symptoms. Most people won’t see a doctor until the cancer has progressed to the point where they cannot ignore the peritoneal mesothelioma symptoms

Peritoneal Cancer Index

The staging system for peritoneal mesothelioma is PCI, or “Peritoneal Cancer Index.” The system divides the abdomen into 13 sections and assigns a score between 0 and 3 to each section, depending on how much disease is present. A score of 0 means there is no cancer in that section, but a score of 3 means the cancer has overtaken it. The scores for each of the 13 sections is totaled up and assigned to a stage. 

PCI scores define each stage as follows:

  • Stage 1 –  PCI score between 1 and 10
  • Stage 2 – PCI score between 11 and 20
  • Stage 3 – PCI score between 21 and 30
  • Stage 4 – PCI score between 31 and higher

The PCI score and equivalent cancer stage help specialists determine a treatment plan. Patients in early stages are more likely to be suitable candidates for cytoreduction surgery with HIPEC. Late stage patients are most likely not surgical candidates but may be offered chemotherapy, immunotherapy or palliative care.

Stage 1 Peritoneal Mesothelioma 

Stage 1 peritoneal mesothelioma is the first stage of this cancer and has the most promising life expectancy. Receiving a stage 1 peritoneal mesothelioma diagnosis means you caught the cancer early, as the tumors have not spread beyond the peritoneum.

Most specialists define a stage 1 peritoneal mesothelioma as a PCI score of 1-10. Unfortunately, a stage 1 peritoneal mesothelioma diagnosis is extremely rare.

The average survival for stage 1 peritoneal mesothelioma is close to two years. Patients diagnosed in stage 1 typically undergo cytoreductive surgery with HIPEC to remove the peritoneum, omentum, any visible tumors in the abdominal cavity, and possibly part of the intestines or other organs, if necessary. A successful cytoreductive surgery with HIPEC can lead to patients living well past their life expectancy.

Stage 2 Peritoneal Mesothelioma 

Stage 2 peritoneal mesothelioma is characterized by tumors beginning to spread into areas of the abdominal cavity. The PCI score correlating to stage 2 peritoneal mesothelioma is 11-20. This means the disease is in no more than half of the abdominal cavity. Stage 2 is still a rare diagnosis for peritoneal mesothelioma, but it does offer hopeful survival and treatment options. 

Peritoneal mesothelioma surgery is still an option for a stage 2 diagnosis. Cytoreductive surgery with HIPEC gives the patient a strong chance of removing most or all of the cancer. By removing the peritoneum, omentum, spleen and any visible tumors in the abdominal cavity, surgeons are removing the tissue containing the tumors, which prevents the cancer from spreading. After the peritoneum removal, doctors will administer HIPEC, a heated chemotherapy treatment, to target any cancer cells remaining after the surgery. This surgery significantly improves a peritoneal mesothelioma patient’s life expectancy.

The stage 2 peritoneal mesothelioma life expectancy is 2-5 years with successful surgery. 

Stage 3 Peritoneal Mesothelioma 

Stage 3 is defined by tumors beginning to spread throughout the abdominal cavity. The PCI score correlating to this stage of peritoneal mesothelioma is 21-30, meaning there are tumors and cancer cells in more than half of the abdominal cavity.

The life expectancy is on average 14-16 months, which is also the average survival for all mesothelioma cases. However, this survival can be improved significantly with successful surgery. 

Cytoreductive surgery with HIPEC can be a treatment option for stage 3 peritoneal mesothelioma. Depending on how widespread the cancer has grown and which organs in the abdominal cavity are affected by tumors, doctors may opt to perform surgery. A successful cytoreduction with HIPEC can add years to a patient’s life expectancy.

Stage 4 Peritoneal Mesothelioma 

Stage 4 peritoneal mesothelioma is the last stage of this cancer. Patients in this stage are often not surgical candidates but may still be offered chemotherapy, immunotherapy or palliative care to increase comfort and maintain quality of life.

The PCI score correlating to stage 4 peritoneal mesothelioma is 31-39, meaning tumors have spread throughout the abdominal cavity. Many of the abdominal organs are likely affected, and most patients are no longer surgical candidates, which significantly reduces their chances for extending survival. Stage 4 peritoneal mesothelioma patients typically receive chemotherapy and may need minimally invasive procedures to provide comfort and pain relief.

The life expectancy for stage 4 peritoneal mesothelioma patients is less than one year.

Symptoms of the Peritoneal Mesothelioma Stages

Symptoms are a key factor in determining the stage of a peritoneal mesothelioma diagnosis. The peritoneal mesothelioma stages present varying symptoms, ranging from nausea to intense abdominal pain.

Symptoms associated with peritoneal mesothelioma in each stage may include:

  • Stage 1 – Nausea, loss of appetite, and mild abdominal pain
  • Stage 2 – Unexplained weight loss, abdominal distention, and fluid buildup in the abdominal cavity
  • Stage 3 – Abdominal pain, nausea, vomiting, fatigue, loss of appetite and weight loss
  • Stage 4 – Intense abdominal pain, severe fatigue, abdominal distention, and chronic fluid buildup in the abdomen

Frequently Asked Questions About Peritoneal Mesothelioma Prognosis

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What Staging System Is Used for Malignant Peritoneal Mesothelioma?

Malignant peritoneal mesothelioma is staged using the Peritoneal Cancer Index (PCI). Doctors score the patient’s disease and can assign it to one of four stages: stage 1, stage 2, stage 3 and stage 4. The PCI score determines how far the tumors have spread within the abdominal cavity, and it usually indicates the extent of the disease, the challenge of surgery, and which organs are affected.

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How is Peritoneal Mesothelioma Staged?

When diagnosing peritoneal mesothelioma, doctors use the Peritoneal Cancer Index (PCI) to stage the cancer. This system divides the abdomen into 13 sections and scores each section depending on the tumor presence. The score is totalled and assigned a stage. For example, a PCI score between 1 and 10 is correlated to stage 1.

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What is the Survival for Each Peritoneal Mesothelioma Stage?

Peritoneal mesothelioma survival is on average 1-2 years. The wide range depends on the stage, treatment options used, and the patient’s overall health. For example, surgery can lead to survival rates of 3-5 years for some patients. There have been many stories of people with peritoneal mesothelioma living for a decade or more.

Sources & Author

  1. Life Expectancy in Pleural and Peritoneal Mesothelioma. Lung Cancer International. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5292397/. Accessed: 03/29/2023.
  2. Predictors and Outcomes of Surgery in Peritoneal Mesothelioma: An Analysis of 2000 Patients From the National Cancer Database. Annals of Surgical Oncology. Retrieved from: https://pubmed.ncbi.nlm.nih.gov/32006127/. Accessed: 03/29/2023.
  3. Peritoneal Cancer Index. Research Gate. https://www.researchgate.net/figure/Peritoneal-Cancer-Index-PCI-scoring-system-PCI-is-a-diagnostic-and-prognostic-tool_fig1_315691686. Accessed: 03/29/2023.
  4. The Accuracy of the Surgical Peritoneal Cancer Index in Patients with Peritoneal Metastases of Colorectal Cancer. Karger. Retrieved from: https://www.karger.com/Article/FullText/513353. Accessed: 03/29/2023.
  5. Peritoneal Mesothelioma. Cleveland Clinic. Retrieved from: https://my.clevelandclinic.org/health/diseases/23973-peritoneal-mesothelioma#diagnosis-and-tests. Accessed: 03/29/2023.
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About the Writer, Camryn Keeble

Camryn Keeble is the senior content writer and editor for Mesothelioma Guide. She creates informative content to educate mesothelioma patients and their loved ones on news, treatments and more. She also works diligently to raise awareness of the dangers of asbestos exposure and the effects of mesothelioma.