Peritoneal Cancer Index: What it Means for Mesothelioma Patients

Treatment // June 21, 2017

Cancer in the abdomen, or peritoneal cancer, is very rare. It occurs when cancer cells develop on the peritoneum, the thin cell lining of the abdominal organs. About 10 – 30% of peritoneal cancer cases occur following a gastric or colon cancer diagnosis. Very rarely this type of cancer will develop on its own, and even then it is often the result of metastasis after a tumor forms elsewhere in the body.

Similarly to peritoneal cancer, peritoneal mesothelioma is very rare, accounting for about 500 new cases each year and only about 15 – 20% of mesothelioma diagnoses. Unlike most forms of peritoneal cancer, peritoneal mesothelioma is not known to be caused by other forms of cancer or the result of metastasis. All types of mesothelioma are caused by exposure to asbestos, through inhalation or ingestion.

Oncologists for peritoneal cancers have relied on the Peritoneal Cancer Index (PCI) for years to help determine a patient’s eligibility for certain kinds of treatment, as well to better understand the severity of the tumors’ progression. PCI has become a notable tool when facing peritoneal mesothelioma, which typically has a poor prognosis and is very often fatal.

What is the Peritoneal Cancer Index?

PCI is a way to determine the extent of the cancer in the abdominal cavity. The cavity is divided into 13 distinct sections, including central, left upper, and pelvic. Each region is “ranked” separately with a lesion size (LS) score depending on the size of the tumors present.

Lesion Size (LS) ScoreSize of the Tumor
0No tumors
1Up to
2Up to 5 cm
3Larger than 5 cm

Patients with an LS score of 3 in a particular region may also have layers or multiple small nodules present. PCI itself is found by adding together the scores for the 13 regions, which makes the highest PCI a 39. Oncologists can determine their score for each region through various imaging tests or laparoscopy. For peritoneal mesothelioma patients, a diagnosis will first need to be confirmed through a peritoneoscopy or laparotomy, which is a tissue biopsy. Doctors will scrutinize the samples to determine the cell type and help examine if the cancerous cells have spread.

PCI is essentially a staging system for peritoneal cancers to help determine if the cancer is localized or has spread to other organs or lymph nodes. Typically, the higher the PCI indicates a worse prognosis as this indicates more, larger tumors present in the body. The PCI will also help oncologists determine if a patient is eligible for certain treatments, particularly surgical removal of the tumors or Hyperthermic Intraperitoneal Chemotherapy (HIPEC).

PCI and Mesothelioma

A “good” or lower PCI for peritoneal mesothelioma patients can mean a better chance of long-term survival. Most oncologists have a cut off score to determine what kind of treatments the patient may be eligible for. In general, a PCI greater than 20 is thought to be too high to see any effective results from HIPEC and the patients would face greater risk undergoing this treatment.

While patients with peritoneal mesothelioma have a longer life expectancy than the other types of mesothelioma, the median survival is still only one year. All types of mesothelioma are generally treated with a combination of surgery, chemotherapy, and radiation. For peritoneal mesothelioma, some of the best results have been seen with a multimodal approach of cytoreductive surgery (surgery to remove as much of the tumors as possible) and HIPEC.

HIPEC is a method of delivering a heated chemotherapy wash to the abdominal cavity. It’s meant to ideally clean out any remaining cancer cells after surgery. HIPEC has been used to treat other abdominal cancers too, including colon and ovarian cancer.

According to a recent study, approximately two-thirds of the peritoneal mesothelioma patients treated this way survived over 3 years. While this may not seem very long, it’s significantly longer than the 1 year median survival rate. In general, there are very few long-term mesothelioma survivors regardless of the type, with only about 33% of patients surviving a year after diagnosis. Any treatment or tool that can better the survival rate is a big accomplishment.

Researchers recognize the advancements in the combination of surgery and HIPEC as the reason for improved survivorship among peritoneal mesothelioma patients in more recent years. Using PCI can make it easier for oncologists to determine the effectiveness of this treatment for an individual’s case.

Research for Better Survival

In the past decade, researchers have made a lot of great advancements in better diagnosing and treating mesothelioma. The peritoneal cancer index is just one tool that can help researchers and peritoneal mesothelioma patients better understand the stage of their disease and the available treatment options.

There is still a lot of work ahead to more effectively treat, and one day cure, this aggressive cancer. But hopefully with the help of established tools like PCI and the advancements made in research today, we will get there soon rather than later.