title: Outcomes of surgery without HIPEC for synchronous peritoneal metastasis from colorectal cancer: data from a multi-center registry.
abstract: BACKGROUND
  Preoperative detection of small peritoneal metastases is difficult, and a convenient method is required to decide the nature of procedures subsequent to initial exploratory surgery. The aim of this study was to validate the Japanese classification of peritoneal metastasis from colorectal cancer.
  
  
  METHODS
  This retrospective study analyzes data from a multi-center registry. Factors affecting the extent of peritoneal metastasis, macroscopic radical resection and prognosis were analyzed using data from patients with colorectal cancer and synchronous peritoneal metastasis. Peritoneal metastasis was classified depending on extent into three groups (P1-P3).
  
  
  RESULTS
  Among 60,176 patients with colorectal surgery, 3,075 (5.1 %) had synchronous peritoneal metastasis. Tumor location on the right side (P < 0.0001), histological grade (P = 0.0014) and distant metastasis (P < 0.0001) were associated with the extent of peritoneal metastasis. Gender (P = 0.041), lymph node metastasis (P < 0.0001), distant metastasis (P < 0.0001), extent of peritoneal metastasis according to the present classification (P < 0.0001) and the period when the patient underwent the operation (operative period; P < 0.0001) were independently associated with macroscopic radical resection. Cox proportional hazards model disclosed that gender (P = 0.0046), tumor location (P = 0.032), age (P = 0.048), histological grade (P < 0.0001), lymph node metastasis (P < 0.0001), distant metastasis (P < 0.0001), extent of peritoneal metastasis (P < 0.0001), and macroscopic radical resection (P < 0.0001) were independent prognostic factors.
  
  
  CONCLUSIONS
  Macroscopic radical resection was an independent prognostic factor even without hyperthermic intraperitoneal chemotherapy. The referral of patients without distant metastasis to centers with experienced peritoneal surgeons might be a potential option if the peritoneal metastasis is unresectable in general hospitals.
authors.affiliation: Center for Minimally Invasive Surgery, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan, h-kobayashi.srg2@tmd.ac.jp.
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Kotake
authors.forename: Kenichi
authors.initials: K
authors.lastname: Sugihara
mesh_terms: D000368:Aged; D015179:Colorectal Neoplasms / Q000473:pathology / Q000601:surgery*; D005260:Female; D006801:Humans; D007564:Japan; D053208:Kaplan-Meier Estimate; D008207:Lymphatic Metastasis / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D010534:Peritoneal Neoplasms / Q000145:classification / Q000473:pathology / Q000556:secondary / Q000601:surgery*; D011379:Prognosis; D016016:Proportional Hazards Models; D016896:Treatment Outcome