Peritoneal metastases from bowel cancer

What it is and what is offered. Spread across the peritoneum, the membrane lining the abdominal cavity, is a distinct pattern of colorectal metastasis and responds poorly to systemic treatment. NICE NG151 (1.5.21) says that for people whose metastases are limited to the peritoneum, systemic anticancer therapy should be offered and the multidisciplinary team should discuss referral to a nationally commissioned specialist centre to consider cytoreductive surgery with hyperthermic intraperitoneal chemotherapy.

What the trial showed. PRODIGE 7 randomised 265 patients at 17 French centres, all of whom had achieved complete macroscopic resection or resection with less than 1 mm of residual tumour, to cytoreductive surgery with or without oxaliplatin hyperthermic intraperitoneal chemotherapy. After a median follow-up of 63.8 months, median overall survival was 41.7 months with the heated chemotherapy and 41.2 months without it (hazard ratio 1.00). Grade 3 or worse adverse events were similar at 30 days but more common in the hyperthermic arm at 60 days (26 against 15 percent). The authors concluded that cytoreductive surgery alone should be the cornerstone of curative-intent treatment (Quenet 2021). The 41-month median survival in both arms is the figure worth carrying: it is the surgery, and the selection of patients fit enough for it with disease complete enough to remove, that produces the outcome.

How to read a referral. Eligibility in the trial required a Peritoneal Cancer Index of 25 or less, performance status 0 or 1, and fitness for six months of systemic chemotherapy. The general glossary term for peritoneal metastasis covers the same pattern in stomach and other cancers, where the trial evidence is different.