Pseudomyxoma peritonei (PMP) is a relatively rare clinical syndrome characterized by neoplastic epithelial cells growing in the peritoneal cavity and secreting mucinous ascites. Our aim was to explore the molecular events behind this fatal but under-investigated disease. We extracted DNA from 19 appendix-derived PMP tumors and nine corresponding normal tissues, and analyzed the mutational hotspot areas of 48 cancer-related genes by amplicon-based next-generation sequencing (NGS). Further, we analyzed the protein expression of V600E mutated BRAF, MLH1, MSH2, MSH6 and p53 from a larger set of PMP tumors (n 5 74) using immunohistochemistry. With NGS, we detected activating somatic KRAS mutations in all of the tumors studied. GNAS was mutated in 63% of the tumors with no marked difference between low-grade and high-grade tumors. Only one (5.3%) tumor showed oncogenic PIK3CA mutation, one showed oncogenic AKT1 mutation, three (15.8%) showed SMAD4 mutations and none showed an APC mutation. P53 protein was aberrantly expressed in higher proportion of high-grade tumors as compared with low-grade ones (31.3 vs. 7.1%, respectively; p 5 0.012) and aberrant expression was an independent factor for reduced overall survival (p 5 0.002). BRAF V600E mutation was only found in one (1.4%) high-grade tumor by immunohistochemistry (n 5 74). All the studied tumors expressed mismatch repair proteins MLH1, MSH2 and MSH6. Our results indicate that KRAS mutations are evident in all and GNAS mutations in most of the PMPs, but BRAF V600E, PIK3CA and APC mutations are rare. Aberrantly expressed p53 is associated with high-grade histology and reduced survival.Pseudomyxoma peritonei (PMP) is a relatively rare subtype of mucinous adenocarcinoma with estimated incidence of one to two persons per million per year. 1 PMP arises most often from mucinous neoplasms of the appendix, which leak tumor cells into the peritoneal cavity, colonize peritoneal cavity and produce abundant mucinous ascites. The classical low-grade (LG) form of PMP has been considered to be a rather benign disease, as it progresses slowly and does not by the definition show invasive characteristics. However, progressive obstruction makes even the LG form of PMP a fatal disease. In contrast, high-grade (HG) PMP possess invasive and metastasizing capacity with the 5-year survival being as low as 23%, while for the LG disease it is 63%. 2 At the moment, the optimal treatment for PMP is aggressive cytoreductive surgery (CRS) followed by hyperthermic intraperitoneal chemotherapy (HIPEC). 3 In addition to PMP-related mortality, these complex treatments are, however, associated with considerable morbidity and mortality. 4 Furthermore, not all patients are amenable to these treatment options. 5 Thus, targeted therapies, even ones that would reduce mucin production, would be important additions to the treatment arsenal for PMP patients. To this end, biomarkers and prognostic factors would be helpful to estimate the aggressiveness of the disease and direct personalized treatment options...

While only 28% of patients underwent initial surgery for presumed PMP, the accuracy of preoperative diagnostics was modest. Diagnostics of PMP is challenging due to the mimicking nature of the disease. In case of indistinct intra-abdominal tumour, we recommend, careful patient examination prior to the initial surgery, when possible.

Key Points Question What is the association of decision aids vs usual care with shared decision-making in men deciding whether to undergo prostate cancer screening? Findings This systematic review and meta-analysis of 19 randomized clinical trials comparing decision aids for prostate cancer screening (12 781 men) found that decision aids are probably associated with a small reduction in decisional conflict and are possibly associated with an increase in knowledge. Decision aids are possibly not associated with whether physicians and patients discuss prostate cancer screening and are possibly not associated with actual screening decisions. Meaning Randomized clinical trials have failed to provide compelling evidence for the use of decision aids for men contemplating prostate cancer screening that have, up to now, undergone rigorous testing to determine their outcome.

IMPORTANCE US guidelines recommend that physicians engage in shared decision-making with men considering prostate cancer screening. OBJECTIVE To estimate the association of decision aids with decisional outcomes in prostate cancer screening.