Peritoneal Carcinomatosis of Colorectal Origin

Abstract

Second to liver, the peritoneum is the most frequent site of metastases in colorectal cancer. In approximately 10% of patients, peritoneal carcinomatosis (PC) is already present at the time of initial diagnosis (1). PC is found in 30% of patients with recurrent colorectal cancer, either as part of more generalized metastases or as the only site. PC is the only site of tumor activity in 40% of cases (2). This means that approximately 8% of all colorectal cancer patients will have PC as their only site of cancer activity at some stage of their disease. PC is generally considered to represent distant metastasis and is staged as M1. Accordingly, until recently, treatment has been limited to palliative surgery, such as enterostomy or bypass to relieve obstruction, and systemic chemotherapy. There are few studies specifically reporting on the outcome of this approach in PC (3). Most studies on chemotherapy in metastatic colorectal cancer include all sites of metastases, with a dominance of liver metastases. Although some reports suggest that colorectal cancers recurring as PC are less likely to respond to systemic chemotherapy, there is little evidence for this. However, there is no doubt that PC patients have a shorter life expectancy than do patients with other metastatic sites, such as liver. This is probably explained by the difficulty in visualizing PC on scans, leading to relatively late diagnosis and the early development of bowel obstruction, even on relatively small tumor volumes. In our series at the Netherlands Cancer Institute, the diagnosis of PC in recurrent cases was made in 80% of patients during laparotomy for bowel obstruction. As a result, many patients will have either a (high output) ileostomy or a relative obstruction, making optimal chemotherapeutic treatment more difficult. In this circumstance, median survival is reported to be between 4 mo and 12 mo (4).