Surgical resection for synchronous peritoneal metastasis from colorectal cancer: A prospective multi-institutional observational study

Background: Synchronous peritoneal metastasis is one of the poor prognostic factors for patients with colorectal cancer. Since the incidence of synchronous peritoneal metastasis from colorectal cancer is low, a single-institutional study is deemed inadequate. This study aimed to investigate the current status of surgical treatment for synchronous peritoneal metastasis from colorectal cancer.
Method: The patients with synchronous peritoneal metastasis from colorectal cancer who underwent surgery at 28 hospitals between 2012 and 2016 were enrolled. A resection rate of synchronous peritoneal metastasis and other clinicopathological features were investigated.
Results: One hundred fifty patients who underwent surgery for colorectal cancer were found to have synchronous peritoneal metastasis. P1:P2:P3 = 30:57:63. A median peritoneal cancer index was 4 (1-29). A median survival time was 1.8 years (0.06-6.5). Eighty-eight patients also had distant metastasis. Among 150 patients, 56 received cytoreductive surgery for peritoneal metastasis. The rate of cytoreductive surgery was 87% in P1, 47% in P2, and 6% in P3, respectively (P<0.0001). The outcomes of patients with cytoreductive surgery was better than those without (P = 0.0005). However, in patients with distant metastasis, there was no difference in overall survival between patients with and without cytoreductive surgery (P = 0.38).
Conclusions: Cytoreductive surgery for synchronous peritoneal metastasis was useful in patients without distant metastasis.