In short
The peritoneal cancer index is a scoring system that helps doctors measure how much cancer has spread throughout the lining of the abdomen, guiding treatment decisions and predicting how likely surgery is to remove all visible tumors.
What is the Peritoneal Cancer Index?
The peritoneal cancer index, commonly abbreviated as PCI, is a tool that doctors use to assess how much cancer has spread within the peritoneal cavity (the space inside the abdomen that contains organs like the stomach, intestines, and liver). The peritoneum is a membrane that lines this abdominal cavity and covers the organs within it.
The PCI was introduced by French surgeon Paul H. Sugarbaker in the 1980s. It is particularly important for cancers that tend to spread along the peritoneum, including ovarian cancer, stomach cancer, colorectal cancer, appendiceal cancer, and peritoneal mesothelioma. This scoring system helps doctors determine a patient's prognosis and plan the most appropriate treatment.
When cancer spreads to the peritoneum from another organ, this condition is called peritoneal carcinomatosis. The PCI is one resource healthcare providers use during the diagnostic process to plan treatment. Using this index, providers map the location of tumors in the abdomen and small intestine, then assign scores based on the tumor size. This information helps providers determine how likely it is that surgery can completely remove all visible tumors.
How the Index is Calculated
The PCI is calculated by dividing the abdomen into 12 distinct regions. Doctors evaluate the size and location of tumors in each of these regions during surgery or through advanced imaging techniques like minimally invasive exploratory surgery (laparoscopy).
The scoring scale ranges from 0 to 39. A higher value indicates a greater extent of disease throughout the peritoneum. Each region is scored individually based on the size of tumor deposits found there, and these individual scores are added together to create the total PCI score.
In some cases, doctors focus on what is called "selected PCI," which evaluates specific regions that are technically challenging to operate on. These include the hepatic hilum (region 2, near the liver) and the small intestine (regions 9-12). These areas are particularly difficult to clear of tumors during surgery. Research has shown that selected PCI can be just as useful as total PCI in predicting whether complete surgical removal is possible, while being simpler and more time-saving in clinical practice.
Clinical Use in Treatment Planning
The peritoneal cancer index serves as an important communication tool between clinicians and radiologists. It helps assess the tumor burden in the peritoneum and can influence a surgeon's decision on whether to perform cytoreductive surgery (surgery aimed at removing all visible cancer), which may be followed by specialized chemotherapy treatments.
PCI assessment is usually performed during minimally invasive exploratory surgery or by advanced imaging techniques. The score helps doctors understand the extent of cancer spread before making decisions about treatment options.
The completeness of cytoreduction is one of the most important factors affecting outcomes for patients with peritoneal cancer. The PCI is used to estimate the tumor load resulting from peritoneal spread, and it shows a negative correlation with the chances of achieving complete tumor removal. This means that the higher the PCI score, the less likely it is that all cancer can be surgically removed.
Predicting Surgical Outcomes
Studies have shown that the PCI is a strong predictor of whether complete cytoreductive surgery can be achieved. Research examining women with advanced stage ovarian cancer found that the PCI predicted incomplete surgery with high accuracy. In one study, patients who had incomplete surgery had a median PCI score of 33 (ranging from 25 to 37), while the median for all patients was 22.
In patients with advanced epithelial ovarian cancer, a PCI cutoff value of 13 was calculated as a threshold above which worse survival is expected. Another study found that only 28.6% of patients with a PCI higher than 33 achieved complete cytoreductive surgery.
Research has also confirmed that when tumors massively involve the small bowel, they are the most common reason for surgeons to perform an "open-close surgery," where the abdomen is opened but the tumor cannot be removed, so the incision is closed without removing the cancer. In one study, massive cancer spread on the small bowel was the reason for open-close surgery in all such cases.
Optimal Cutoff Points for Different Cancers
The optimal PCI cutoff point differs between different types and grades of cancer. Research on pseudomyxoma peritonei (PMP), a rare cancer condition, found that the cutoff points vary between low-grade and high-grade disease because low-grade patients are more likely to achieve complete surgical removal when the tumor load is equivalent.
For low-grade PMP patients, both total PCI and selected PCI demonstrated excellent ability to predict surgical resectability. The optimal cutoff point for total PCI was 21, while for selected PCI it was 5.
For high-grade PMP patients, the optimal cutoff point for total PCI was 25, and for selected PCI it was 8. Both total and selected PCI exhibited good performance and similarity in predicting complete surgical resection for both low-grade and high-grade PMP patients.
In advanced stage serous epithelial ovarian cancer, one study found that patients with PCI scores higher than 24 had a 67.2% chance of achieving complete cytoreductive surgery, though they also experienced an increased rate of complications.
