title: Histological subtype and systemic metastases strongly influence treatment and survival in patients with synchronous colorectal peritoneal metastases.
abstract: Treatment possibilities for colorectal peritoneal metastases (PM) are increasing. It is however unclear how treatment choice and outcome are influenced by histological subtype and the presence of systemic metastases. Therefore, this study assessed the impact of histological subtype and systemic metastases on treatment choice and survival in patients with colorectal PM.
  
  
  
  This population-based study included patients with synchronous PM originating from colorectal adenocarcinoma (AC), mucinous adenocarcinoma (MC), or signet ring cell carcinoma (SRCC). Data of patients diagnosed between 2005 and 2014 were extracted from the National Cancer Registry (IKNL) of the Netherlands. Treatment strategy and survival were analyzed with logistic regression and cox proportional hazard analyses.
  
  
  
  In total, 5516 patients were included, of whom 71.8% had an AC, 21.2% an MC, and 7.0% had an SRCC. The use of cytoreduction and hyperthermic intraperitoneal chemotherapy (HIPEC) was dependent on histological subtype and the presence of systemic metastases, and increased over time, especially in AC and MC patients. The relative survival gain of CRS + HIPEC, corrected for systemic metastases, was comparable in AC, MC, and SRCC patients (hazard ratio: 0.17, 0.21, and 0.13, respectively). Compared to supportive care only, the absolute survival gain was 30, 35, and 18 months, respectively. Systemic therapy improved survival in all histological subtypes.
  
  
  
  Histological subtype and the presence of systemic metastases strongly influenced treatment choice and survival in patients with synchronous colorectal PM. These results can be used to optimize treatment strategy for patients with synchronous colorectal PM.
authors.affiliation: Department of Surgical Oncology, Catharina Hospital, PO Box 1350, 5602 ZA Eindhoven, The Netherlands. Electronic address: geert.simkens@catharinaziekenhuis.nl.
authors.forename: G A
authors.initials: GA
authors.lastname: Simkens
authors.affiliation: Department of Oncology, Catharina Hospital, PO Box 1350, 5602 ZA Eindhoven, The Netherlands; Netherlands Comprehensive Cancer Organization (IKNL), PO Box 19079, 3501 DB Utrecht, The Netherlands.
authors.forename: L G
authors.initials: LG
authors.lastname: Razenberg
authors.affiliation: Netherlands Comprehensive Cancer Organization (IKNL), PO Box 19079, 3501 DB Utrecht, The Netherlands; Department of Public Health, Erasmus MC University Medical Centre, PO Box 2040, 3000 CA Rotterdam, The Netherlands.
authors.forename: V E
authors.initials: VE
authors.lastname: Lemmens
authors.affiliation: Department of Surgical Oncology, Catharina Hospital, PO Box 1350, 5602 ZA Eindhoven, The Netherlands.
authors.forename: H J
authors.initials: HJ
authors.lastname: Rutten
authors.affiliation: Department of Oncology, Catharina Hospital, PO Box 1350, 5602 ZA Eindhoven, The Netherlands.
authors.forename: G-J
authors.initials: GJ
authors.lastname: Creemers
authors.affiliation: Department of Surgical Oncology, Catharina Hospital, PO Box 1350, 5602 ZA Eindhoven, The Netherlands. Electronic address: ignace.d.hingh@catharinaziekenhuis.nl.
authors.forename: I H
authors.initials: IH
authors.lastname: de Hingh
mesh_terms: D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D010478:Chemotherapy, Cancer, Regional Perfusion / Q000379:methods; D015179:Colorectal Neoplasms / Q000401:mortality / Q000473:pathology* / Q000628:therapy*; D065426:Cytoreduction Surgical Procedures; D005260:Female; D006801:Humans; D006979:Hyperthermia, Induced; D008297:Male; D008875:Middle Aged; D010534:Peritoneal Neoplasms / Q000401:mortality / Q000556:secondary* / Q000628:therapy*; D016019:Survival Analysis; D016896:Treatment Outcome
keywords: Chemotherapy; Colorectal neoplasms; Cytoreductive surgery; HIPEC; Peritoneal carcinomatosis; Peritoneal metastases