What Is Peritoneal Mesothelioma?

Peritoneal mesothelioma is a type of cancer that develops in the peritoneum, a thin layer of tissue that lines the abdominal cavity and covers organs like the stomach, intestines, and liver. It’s caused primarily by exposure to asbestos, a mineral once widely used in construction and manufacturing. When asbestos fibers are inhaled or ingested, they can become lodged in the peritoneum, causing irritation and, over time, leading to cancer. This process can take 20 to 60 years, which is why symptoms often appear decades after exposure.

 

Common symptoms of peritoneal mesothelioma include:

 

• Abdominal pain or discomfort
• Swelling or bloating in the abdomen (often due to fluid buildup, called ascites)
• Weight loss
• Nausea or digestive issues
• Fatigue

Because these symptoms are vague and can mimic other conditions, such as irritable bowel syndrome or ovarian cancer, peritoneal mesothelioma is often diagnosed at a later stage. This makes tools like the PCI especially important for understanding the disease’s progression and planning treatment.

What Is the Peritoneal Cancer Index (PCI)?

The Peritoneal Cancer Index, or PCI, is a scoring system used by doctors to measure the extent of cancer spread within the abdominal cavity. Think of it as a map that helps doctors see how much cancer is present and where it’s located. The PCI was first developed by Dr. Paul Sugarbaker to assess cancers that spread across the peritoneal surfaces, such as peritoneal mesothelioma, colorectal cancer, and ovarian cancer.

 

The PCI divides the abdomen and pelvis into 13 regions, including areas like the upper abdomen, lower abdomen, and pelvis. During surgery or through imaging tests like a CT scan, doctors evaluate each region for the presence of cancer. They assign a score from 0 to 3 based on the size and extent of tumors in each area:

 

• 0: No cancer is visible.
• 1: Tumors are small (less than 0.5 cm).
• 2: Tumors are moderate (0.5 to 5 cm).
• 3: Tumors are large (greater than 5 cm) or there’s extensive cancer spread.

 

The scores from all 13 regions are added up to give a total PCI score, which ranges from 0 to 39. A lower score indicates less cancer spread, while a higher score suggests more extensive disease. This score helps doctors determine whether treatments like surgery or chemotherapy are likely to be effective.

Why Is the PCI Important for Peritoneal Mesothelioma?

For patients with peritoneal mesothelioma, the PCI is a critical tool because this cancer tends to stay within the abdominal cavity rather than spreading to distant parts of the body. Unlike other cancers that might metastasize to the lungs or bones, peritoneal mesothelioma often grows as many small tumors across the peritoneal surfaces. This makes it challenging to assess without a structured system like the PCI.

 

Here’s why the PCI matters for peritoneal mesothelioma:

 

1. Guides Treatment Decisions: The PCI helps doctors decide if a patient is a good candidate for cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC). CRS involves removing visible tumors, while HIPEC delivers heated chemotherapy directly into the abdomen to kill remaining cancer cells. If the PCI score is too high (indicating widespread cancer), surgery may not be as effective, and other treatments, like systemic chemotherapy, might be recommended instead.
2. Predicts Prognosis: A lower PCI score is associated with better outcomes. For example, patients with a PCI score below 20 are more likely to benefit from CRS and HIPEC, with some surviving 5 years or more. Higher scores may indicate a more aggressive disease, which can affect life expectancy.
3. Monitors Disease Progression: The PCI can be used before and after treatment to track how the cancer responds to therapy. A decrease in the PCI score after treatment suggests that the cancer is shrinking, while an increase may indicate recurrence.How Is the PCI Measured?

The PCI is typically calculated during a surgical procedure called diagnostic laparoscopy, where a small camera is inserted into the abdomen to visualize the cancer. This allows doctors to directly see and score the extent of tumor spread in each of the 13 regions. In some cases, imaging tests like CT or MRI scans can provide an estimate of the PCI, but these are less accurate because they may miss small tumors.

 

During laparoscopy, the surgeon examines areas such as:

 

• The omentum (a fatty layer covering the abdominal organs)
• The small and large intestines
• The liver and stomach surfaces
• The pelvic region

The surgeon assigns a score to each region based on the size and number of tumors. For example, if the omentum has large tumors (greater than 5 cm), it might receive a score of 3. If another region, like the lower abdomen, has no visible cancer, it gets a score of 0. The total score helps paint a picture of how widespread the cancer is.

PCI and Treatment Options for Peritoneal Mesothelioma

The PCI score plays a big role in determining the best treatment plan for peritoneal mesothelioma. Here’s how it influences the main treatment options:

 

1. Cytoreductive Surgery (CRS) and HIPEC

For patients with a PCI score of 20 or lower, CRS combined with HIPEC is often the preferred treatment. This approach has been shown to significantly improve survival, with some patients living 5 years or more after treatment. During CRS, surgeons remove as much visible cancer as possible, including tumors on the peritoneum and affected organs. HIPEC then delivers heated chemotherapy directly into the abdomen to target any remaining cancer cells. The heat enhances the chemotherapy’s effectiveness, and the direct delivery minimizes side effects to the rest of the body.

The success of CRS and HIPEC depends on achieving complete cytoreduction, meaning no visible cancer remains (scored as CC-0) or only tiny tumors less than 2.5 mm remain (CC-1). A lower PCI score increases the chances of complete cytoreduction, which is why the PCI is so important.

 

2. Systemic Chemotherapy

For patients with a higher PCI score (above 20) or those who aren’t candidates for surgery due to health issues, systemic chemotherapy may be recommended. This involves drugs like pemetrexed and cisplatin, which are given through an IV to target cancer cells throughout the body. While systemic chemotherapy can help control symptoms and slow disease progression, it’s less effective than CRS and HIPEC for peritoneal mesothelioma.

 

3. Immunotherapy and Other Treatments

Newer treatments, such as immunotherapy, are being explored for peritoneal mesothelioma. Immunotherapy helps the body’s immune system recognize and attack cancer cells. Clinical trials are also investigating other approaches, like targeted therapies and oncolytic virus therapy, which uses viruses to destroy cancer cells.

 

4. Palliative Care

For patients with very high PCI scores or advanced disease, palliative care focuses on improving quality of life by managing symptoms like pain, ascites, and digestive issues. This may include procedures to drain fluid from the abdomen or medications to relieve discomfort.

PCI in Other Cancers

While the PCI is widely used for peritoneal mesothelioma, it’s also an important tool for assessing other cancers that spread to the peritoneum, a condition known as peritoneal carcinomatosis. These cancers include:

 

• Ovarian Cancer: The PCI helps evaluate the spread of ovarian cancer within the abdominal cavity, guiding decisions about surgery and chemotherapy. A lower PCI score is associated with better outcomes in ovarian cancer patients.
• Colorectal Cancer: When colorectal cancer spreads to the peritoneum, the PCI helps determine if cytoreductive surgery and HIPEC are viable options. Studies have shown that a PCI score below 20 is linked to better survival in these cases.
• Appendiceal Cancer: Cancers of the appendix, such as mucinous adenocarcinoma, often spread to the peritoneum. The PCI is used to assess the extent of disease and plan treatments like HIPEC.
• Gastric Cancer: For stomach cancer that has spread to the peritoneum, the PCI helps doctors decide whether surgery is feasible or if systemic treatments are more appropriate.
• Pseudomyxoma Peritonei: This rare condition, often caused by appendiceal tumors, involves the buildup of mucin (a jelly-like substance) in the abdomen. The PCI is used to evaluate the extent of disease and guide surgical treatment.

In all these cancers, the PCI provides a standardized way to measure disease burden and predict how well a patient might respond to treatment. It’s particularly useful for cancers that stay confined to the abdominal cavity, similar to peritoneal mesothelioma.

Factors That Affect PCI and Prognosis

Several factors can influence a patient’s PCI score and overall prognosis for peritoneal mesothelioma:

 

• Tumor Type: Peritoneal mesothelioma has different subtypes, including epithelioid, sarcomatoid, and biphasic. Epithelioid mesothelioma tends to have a better prognosis and lower PCI scores compared to the more aggressive sarcomatoid type.
• Age and Overall Health: Younger patients and those in good general health are more likely to have lower PCI scores and tolerate aggressive treatments like CRS and HIPEC.
• Asbestos Exposure: The extent and duration of asbestos exposure can affect how aggressive the cancer is and how widely it spreads.
• Lymph Node Involvement: If the cancer has spread to lymph nodes, it may increase the PCI score and worsen the prognosis.
• Previous Treatments: Patients who have had prior surgeries or chemotherapy may have higher PCI scores due to scarring or disease progression.

Challenges in Using the PCI

While the PCI is a valuable tool, it’s not perfect. Here are some challenges:

 

• Imaging Limitations: CT or MRI scans may underestimate the PCI because they can miss small tumors. Laparoscopy is more accurate but requires a surgical procedure.
• Subjectivity: Different surgeons or radiologists may interpret the size and extent of tumors slightly differently, which can affect the PCI score.
• Complexity of Mesothelioma: Peritoneal mesothelioma doesn’t fit neatly into traditional cancer staging systems like TNM (Tumor, Node, Metastasis) because it rarely spreads beyond the abdomen. The PCI helps fill this gap, but it’s still just one piece of the puzzle.

What Patients Can Do

If you or a loved one has been diagnosed with peritoneal mesothelioma, understanding the PCI can empower you to have informed discussions with your healthcare team. Here are some steps you can take:

 

1. Ask About Your PCI Score: If your doctor recommends surgery or imaging, ask if they’ve calculated your PCI score and what it means for your treatment options.
2. Seek a Specialist: Peritoneal mesothelioma is rare, so it’s important to work with a doctor who specializes in this disease. Mesothelioma centers, like those at academic hospitals, often have experience with CRS and HIPEC.
3. Explore Clinical Trials: If your PCI score is high or standard treatments aren’t an option, ask about clinical trials for new therapies like immunotherapy.
4. Focus on Quality of Life: Work with your healthcare team to manage symptoms like pain or ascites, which can improve your comfort and well-being.

Living with Peritoneal Mesothelioma

A diagnosis of peritoneal mesothelioma can feel overwhelming, but advances in treatment have improved outcomes for many patients. The PCI is a key tool that helps doctors tailor treatments to your specific situation, whether that’s surgery, chemotherapy, or palliative care. By understanding your PCI score and working closely with your medical team, you can make informed decisions about your care.

 

For example, patients with a low PCI score who undergo CRS and HIPEC have a 5-year survival rate of about 65% in some studies. Even for those with higher PCI scores, new treatments like immunotherapy are offering hope. Support groups and resources from organizations like the Mesothelioma Applied Research Foundation can also provide emotional and practical support.

Conclusion

The Peritoneal Cancer Index is a powerful tool that helps doctors assess the spread of peritoneal mesothelioma and other cancers in the abdominal cavity. By providing a clear picture of how much cancer is present, the PCI guides treatment decisions and offers insight into a patient’s prognosis. For peritoneal mesothelioma, it’s especially important, making targeted treatments like CRS and HIPEC effective for many patients. The PCI is also used for other cancers, such as ovarian, colorectal, and appendiceal cancers, helping doctors plan the best course of action.

 

If you’re facing a diagnosis of peritoneal mesothelioma, talk to your doctor about the PCI and how it applies to your case. With the right treatment plan and support, you can navigate this challenging journey with hope and confidence.