Peritoneal carcinomatosis resulting from metastatic colorectal cancer (pcCRC) is a relatively common and under recognized condition with a very poor prognosis. The presentation of pcCRC is distinct from hepatic or pulmonary metastases yet most studies do not differentiate CRC subtypes. The lack of a widely recognized subclassification of metastatic CRC is problematic because fatal complications vary according to the involved site. Jan Franko and his team therefore decided to characterize the outcomes of 2,101 patients with or without pcCRC in two prospective randomized trials. They showed that the overall survival and progression-free survival was significantly reduced for patients with pcCRC compared with those lacking carcinomatosis.

As the researchers explain, “this report is by far the largest and is, to our knowledge, the only study that analyzes survival differences on the basis of pcCRC status”. Franko further elaborates, “carcinomatosis is associated with consistently shorter survival by about 30%, which is in agreement with findings from observational studies. Systemic chemotherapy works among patients with pcCRC and provides the same relative benefit as those without pcCRC, which refutes the notion that systemic chemotherapy is ineffective in carcinomatosis.” Thus, the presence or absence of pcCRC should not affect the choice of chemotherapy, and future trials of metastatic CRC should consider stratification on the basis of pcCRC status.

Franko's team plan to develop a subclassification of metastatic CRC in order to predict the most likely life-altering complications from metastatic pcCRC, which would help avoid these complications and ultimately prolong patient survival.