Classification of extensiveness / peritoneal cancer index (PCI)
Peritoneal carcinomatosis varies from nearly microscopic to kilogram scale interperitoneal tumor tissue. It is therefore important to have a classification system to compare studies from various centers.
At the Norwegian Radium Hospital, we have used the Sugarbaker's method for the past few years. The abdomen is separated into 9 regions. The extent in each region is described based on the size of the lesion. The small intestine is separated in the same way into 4 regions. In each of the 13 areas, the size of the lesion is described on a scale from 0 to 3. This is then calculated as Peritoneal Carcinomatosis Index (PCI), which is the sum of the lesion sizes from all 13 areas. PCI index may be between 0 and 39.
Regions and scoring used for calculating Peritoneal Carcinomatosis Index (PCI).
Classification of surgical result / degree of cytoreduction
There exist multiple classification systems. Complete surgical radicality (R0) is in some systems equivalent to removal of all visible tumor tissue, while others accept that tumors thinner than than 2.5 mm may remain (CC–0/CC–1). It is expected that such small tumours may be killed by the intraperitoneal chemotherapy which is supposed to diffuse 2 mm into the tissue. Some describe full surgical radicality (R0) which is synonymous with removal of all visible tumor tissue. In another widely used staging system, surgical cytoreduction denoted as CC-0 is used if there is no remaining tumor, and CC-1 if the largest residual tumor is less than 2.5 mm. CC-2 indicates residual tumor up to 2.5 cm, and CC-3 indicates a larger residual lesion. The background for this staging is that chemotherapy will apparently disperse 2-3 mm in the tissue.