br Conclusion br Declaration of interest This project was fu
Declaration of interest This project was funded by the Richdale Charitable Trust. The funder had no role in the design, analysis, interpretation, write-up or publication of this study.
Introduction Malignant mesothelioma is a rare disease that results from the transformation of mesothelial AMG-176 that line the serosal surfaces. It represents 0.2% of all cancers  and has a dismal prognosis with few therapeutic options. Mesothelioma is much more frequent in men than in women (ratio 3.7:1) . It is strongly associated with asbestos exposure (up to 90% of male cases ), and can develop in the pleura (the most frequent location, 90%), the peritoneum (10%), and rarely in the tunica vaginalis testis and pericardium . Due to its rarity, trends in peritoneal mesothelioma among men and women are not as extensively described as for pleural mesothelioma. Between 1971 and 1995, the incidence of peritoneal mesothelioma was estimated to 0.02–0.3 cases per 100,000 persons-years in the US and Europe. Age world-standardized rates per 100,000 persons-years range from 0.05–0.3 cases in men to 0.02–0.2 in women . A study carried out in 2011, the RARECARE study, estimated the incidence between 1995 and 2002 at 0.12 cases per 100,000 persons-years in Europe . The 5-year overall and relative survivals reported by the RARECARE study between 1995 and 2002 and were 9.8% and 11.4%, respectively . The mechanisms of carcinogenesis in peritoneal malignant mesothelioma have not been definitively elucidated , limiting the therapeutic options. Nevertheless, the combined treatment of cytoreductive surgery with hyperthermic intraperitoneal chemotherapy can offer prolonged survival for selected patients, increasing the 5-year overall survival to 47% .
Material and methods
Discussion In this study we report for the first time the patients’ characteristics and long-term trends in the incidence and survival of peritoneal malignant mesothelioma in France from the population-based cancer registries, using data available since 1989. Peritoneal mesothelioma is a rare disease that histologically mimics other cancers, causing frequent misdiagnosis that may result in epidemiological discordances. Thanks to advances in biological and histological knowledge of this tumor and the establishment in France in 1998 of a standardized procedure for certification of the diagnosis of mesothelioma, diagnostic accuracy has improved, as has in consequence the coding and assessment of incidence, reducing epidemiological bias . In our series, the risk of misclassification is minimal. We found that, contrary to pleural malignant mesothelioma (ratio of men to women of about 4:1 between 1989 and 2003 and 3:1 since 2003 [3,9,10,, , ]), peritoneal mesothelioma develops almost equally in both men and women. In French men, the incidence has been slowly increasing since 1989 from 0.07 per 100,000 persons-years in the period 1989–1991 to 0.10 in 2012–2015, with a maximum rate of 0.16 in 2001–2003. For women, this rate increased faster than for men over the period 1989–2015, fluctuating between 0.04 and 0.11. These findings were consistent with results recently published in Europe ; in particular, the male incidence per 100,000 persons-years in Lombardy had two peaks, one in 2001 (0.17) and one in 2010 (0.19) , and this has also been observed in France. If we compare our results with those obtained in a parallel study of the pleural counterpart in similar population settings and data sources , we notice that the clinical behavior of these two mesothelioma localizations is clearly different. The median OS is 11.7 months in peritoneum and 10.6 months in pleura. Only 4% of men and 11% of women affected by pleural mesothelioma are alive 5 years after diagnosis, against 13% of men and 34% of women with peritoneal mesothelioma. The 1-year survival rate is similar for both diseases, reflecting the high lethality of these diseases regardless of their location; however, the proportion of long-term survivors is larger in peritoneal mesothelioma cases [17,18]. The main individual characteristics associated with 5-year survival, regardless of age, are: female gender, epithelioid morphology, and diagnosis after 2000. Regarding the results for the histological type, the devastating prognosis of biphasic or sarcomatoid types (also called fibrous for cancer registries) is well established [, , ].