Development of lung metastases after curative intraperitoneal chemotherapy in a rat colon cancer model

A model of colon peritoneal carcinomatosis was developed by injecting 5 x 10(7) viable tumor cells intraperitoneally into Fisher 344 rats. All 40 control rats developed bulky abdominal tumor with ascites and died of peritoneal carcinomatosis and bowel obstruction (median survival 5 weeks). One day after tumor implantation, treatment group rats received a single intraperitoneal injection of single agent or combination chemotherapy. The most active intraperitoneal single agents were 5-fluorouracil, cisplatin, and etoposide. The most active combination was 5-fluorouracil and cisplatin. Combination chemotherapy produced a significant increase in median, 10-week, and 20-week survival (vs control and single agent). Six of 11 (55%) rats treated with intraperitoneal combination chemotherapy dying between 10-20 weeks died of lung metastasis with cure of intraperitoneal tumor. The increased ability of intraperitoneal combination chemotherapy to cure intraperitoneal disease was offset by the development of lung metastasis.