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Background: KRAS and BRAF mutations are prognostic and predictive tools in metastatic colorectal cancer, but little is known about their prognostic value in patients scheduled for cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). Therefore, we analyzed the prognostic impact of KRAS and BRAF mutations in patients with peritoneal metastases scheduled for CRS and HIPEC., Patients and Methods: In a consecutive series of 399 patients scheduled for CRS and HIPEC between 2009 and 2017, 111 subjects with peritoneal metastases from primaries of the appendix, colon, or rectum were analyzed for KRAS mutation and 92 for BRAF mutation., Results: Mutation in KRAS was present in 51/111 (46%), and mutated BRAF was found in 10/92 (11%). There was no difference in overall survival between KRAS mutation tumors and KRAS wild type, whereas BRAF mutation was associated with short survival. No subject with BRAF mutation survived 2 years. On multivariate analysis, completeness of cytoreduction score (CCS, p = 0.000001), presence of signet cell differentiation (p = 0.000001), and BRAF mutation (p = 0.0021) were linked with poor prognosis., Conclusions: BRAF mutation is a marker of poor prognosis in patients with appendiceal and colorectal peritoneal metastases scheduled for CRS and HIPEC, whereas survival outcome in subjects with mutated KRAS does not differ from wild-type KRAS. This finding suggests that those with BRAF mutation should be considered for alternative treatment options.

Background: Early diagnosis to target minimal volume disease has received increased attention in the management of appendiceal and colorectal peritoneal metastases (PM). This study aimed to identify risk factors for appendiceal, colon and rectal PM., Methods: Data were retrieved from the Swedish Colorectal Cancer Registry for all patients undergoing bowel resection of appendiceal and colorectal tumours, in Sweden, 2007-2015. Risk factors for synchronous and metachronous PM were analysed with multivariate logistic and Cox proportional hazard regression models., Results: Synchronous PM was most common in appendiceal cancer (23.5%), followed by colon (3.1%) and rectal (0.6%) cancer. The 5-year cumulative incidence was 9.0% for appendiceal, 2.5% for right colon, 1.8% for left colon and 1.2% for rectal cancer. In appendiceal cancer (n = 327), T4, N2, mucinous tumour, and non-radical surgery were associated with PM. In colon cancer (n = 24,399), synchronous PM were primarily associated with T4 (OR 18.37, 95% CI 8.12-41.53), T3 and N2 but also with N1, right-sided tumour, mucinous tumour, vascular and perineural invasion, female gender, age <60 and emergency surgery. These factors were also associated with metachronous PM. In rectal cancer (n = 10,394), T4 (OR 19.12, 95% CI 5.52-66.24), proximal tumour and mucinous tumour were associated with synchronous PM and T4 and mucinous tumour with metachronous PM., Conclusions: This study shows that appendiceal cancer, right-sided colon cancer, advanced tumour and node stages and mucinous histopathology are the main high-risk features for PM and should increase the awareness of current or future PM., (Copyright © 2018 Elsevier Ltd, BASO ~ The Association for Cancer Surgery, and the European Society of Surgical Oncology. All rights reserved.)

Background: The importance of absent neoplastic epithelium in specimens from cytoreductive surgery (CRS) is unknown. This study aimed to investigate the prevalence and prognostic value of histopathology without neoplastic epithelium in patients treated with CRS and hyperthermic intraperitoneal chemotherapy (HIPEC)., Methods: Data were extracted from medical records and histopathology reports for patients treated with initial CRS and HIPEC at Uppsala University Hospital, Sweden, between 2004 and 2012. Patients with inoperable disease and patients undergoing palliative non-CRS surgery were excluded from the study. Patients lacking neoplastic epithelium in surgical specimens from CRS, with or without mucin, were classified as "neoplastic epithelium absent" (NEA), and patients with neoplastic epithelium were classified as "neoplastic epithelium present" (NEP)., Results: The study observed NEA in 78 of 353 patients (22 %). Mucin was found in 28 of the patients with NEA. For low-grade appendiceal mucinous neoplasms and adenomas, the 5-year overall survival rate was 100 % for NEA and 84 % for NEP, and the 5-year recurrence-free survival rate was 100 % for NEA and 59 % for NEP. For appendiceal/colorectal adenocarcinomas (including tumors of the small intestine), the 5-year overall survival rate was 61 % for NEA and 38 % for NEP, and the 5-year recurrence-free survival rate was 60 % for NEA and 14 % for NEP. Carcinoembryonic antigen level, peritoneal cancer index, and completeness of the cytoreduction score were lower in patients with NEA., Conclusions: A substantial proportion of patients undergoing CRS and HIPEC have NEA. These patients have a favorable prognosis and a decreased risk of recurrence. Differences in patient selection can affect the proportion of NEA and hence explain differences in survival rates between reported series.