Peritoneal carcinomatosis of gastric origin: A population-based study on incidence, survival and risk factors Irene Thomassen 1,2 , Yvette R. van Gestel 2 , Bert van Ramshorst 3 , Misha D. Luyer 1 , Koop Bosscha 4 , Simon W. Nienhuijs 1 , Valery E. Lemmens 2,5 and Ignace H. de Hingh 1 1 Department of Surgery, Catharina Hospital, Eindhoven, The Netherlands 2 Eindhoven Cancer Registry, Comprehensive Cancer Centre South (IKZ), Eindhoven, The Netherlands 3 Department of Surgery, St. Antonius Hospital, Nieuwegein, The Netherlands 4 Department of Surgery, Jeroen Bosch Hospital ‘s Hertogenbosch, The Netherlands 5 Department of Public Health, Erasmus MC University Medical Centre, Rotterdam, The Netherlands Peritoneal carcinomatosis (PC) is an important cause of morbidity and mortality among patients with gastric cancer. The aim of the current study was to provide reliable population-based data on the incidence, risk factors and prognosis of PC of gastric origin. All patients diagnosed with gastric cancer in the area of the Eindhoven Cancer Registry between 1995 and 2011 were included. Incidence and survival were computed and risk factors for peritoneal carcinomatosis were determined using multivar- iate logistic regression analysis. In total, 5,220 patients were diagnosed with gastric cancer, of whom 2,029 (39%) presented with metastatic disease. PC was present in 706 patients (14%) of whom 491 patients (9%) had PC as the only metastatic site. Younger age (<60 years), female gender, advanced T- and N-stage, primary tumor of signet ring cells or linitis plastica and pri- mary tumors covering multiple anatomical locations of the stomach were all associated with a higher odds ratios of develop- ing PC. Median survival of patients without metastases was 14 months, but only 4 months for patients with PC. PC is a frequent condition in patients presenting with gastric cancer, especially in younger patients with advanced tumor stages. Given the detrimental influence of PC on survival, efforts should be undertaken to further explore the promising results that were obtained in preventing or treating this condition with multimodality strategies. Gastric cancer is known for its aggressive natural history and is the second main cause of death from cancer worldwide accounting for 740,000 deaths per year. 1 Incidence rates of gastric cancer vary throughout the world, with two-thirds occurring in developing countries. Peritoneum and liver are the most common metastatic sites among patients with gas- tric cancer. Peritoneal carcinomatosis (PC) can lead to bowel obstruction and formation of massive amounts of malignant ascites, invariably resulting in death. In spite of its grave con- sequences, the incidence of PC in gastric cancer is currently unknown. To date, only institution-based data reporting on gastric cancer patients being explored for potentially curative resection or with advanced gastric cancer are available. 2–6 Population-based data on the incidence of PC from gastric origin are lacking. Until recently, PC of gastric origin was regarded to be an untreatable condition with a poor quality of life and short life expectancy. However, new chemotherapeutic regimens including 5-FU, anthracyclines and cisplatin demonstrated a benefit in overall survival compared to strategies without these agents, as was shown in a recent meta-analysis. 7 Fur- thermore, a combined strategy of cytoreductive surgery and intraperitoneal chemotherapy showed favorable results in highly selected patients. 8 This multimodality treatment is cur- rently regarded as the only therapeutic option for selected patients with PC from gastric cancer, reporting 5-year sur- vival rates ranging from 13 to 28%. 9–11 With the emergence of possible treatment strategies for patients with PC of gastric origin, reliable information on the scope of this condition will become of increasing importance. Therefore, the aim of the current study was to provide reli- able population-based data on its incidence and prognosis, and to identify risk factors for the development of PC. Methods The Eindhoven Cancer Registry registers all newly diagnosed cancer patients in the southern part of the Netherlands. This area includes 10 community hospitals, six pathology depart- ments and two radiotherapy institutions, comprising 2.4 mil- lion inhabitants. All patients diagnosed between 1995 and 2011 with an adenocarcinoma of gastric origin in the Key words: gastric cancer, peritoneal carcinomatosis, metastasis, incidence, treatment, prognosis DOI: 10.1002/ijc.28373 History: Received 20 Mar 2013; Accepted 17 June 2013; Online 5 Jul 2013 Correspondence to: Ignace de Hingh, Department of Surgery, Catharina Hospital Eindhoven, Michelangelolaan 2, 5623 EJ Eindhoven, The Netherlands, Tel.: 131 40 2399111, Fax: 131 40 2455035, E-mail: ignace.d.hingh@cze.nl Epidemiology Int. J. Cancer: 00, 00–00 (2013) V C 2013 UICC International Journal of Cancer IJC