External multicentre validation of pseudomyxoma peritonei PSOGI-Ki67 classification.

BACKGROUND: Pseudomyxoma peritonei (PMP) is a rare malignant disease. Adding of the Ki67 proliferation index to the PSOGI PMP classification provided two different subcategories of the extensive HG-PMP group (HG-PMP ≤15% and HG-PMP >15%) with different survival in a previous unicentric study. This study aims to carry out an external and multicentre validation of this new proposed classification. METHOD: It was a prospective analysis of samples from a historical and international cohort of patients. A representative area with higher cellular density was used to determine the Ki67%. The Ki67 proliferation index (%) was determined in all the HG-PMP patients. A Cox proportional hazard models and multivariable COX models were used. The Kaplan-Meier method and the two-tailed log-rank test were used to analyse the effect of different PSOGI-Ki67 categories on OS and DFS. Its predictive accuracy was analysed using Harrel's C-index and the ROC curve. The calibration was performed using the calibration plots matching. RESULTS: After exclusions, 349 patients were available for analysis. The 5-years OS were 86% for LG-PMP, 59% for HG-PMP≤15, 38% for HG-PMP>15 and 42% for SRC-PMP (p = 0.0001). The 5-years DFS were 49% for LG-PMP, 35% for HG-PMP≤15, 16% for HG-PMP>15 and 18% SRC-PMP (p = 0.0001). The discrimination capability of PSOGI-Ki67 was validated. CONCLUSION: the PSOGI-Ki67 classification discriminates and predicts the OS and DFS in patients with PMP dividing the HG-PMP category into two well-defined sub-categories. The Ki67 proliferation index should be incorporated routinely in the pathology report for these patients.

Validation of a Nomogram to Predict Recurrence in Patients with Mucinous Neoplasms of the Appendix with Peritoneal Dissemination After Cytoreductive Surgery and HIPEC.

BACKGROUND: Survival of patients affected by mucinous appendiceal neoplasms with peritoneal dissemination (PD) is mainly related to histopathological features. However, prognostic stratification is still a concern, as the clinical course of the disease is often unpredictable. The aim of this study is to construct and externally validate a nomogram predicting disease-free survival (DFS) in mucinous appendiceal neoplasms with PD treated by cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC). PATIENTS AND METHODS: Patients treated in two referral centers were included: Hospital General Universitario Gregorio Marañón, Madrid, Spain (derivation cohort) and Fondazione IRCCS Istituto Nazionale Tumori, Milan, Italy (validation cohort). Cox regression analysis identified factors associated with shorter DFS in the derivation cohort. The nomogram performance was externally evaluated in the validation cohort using concordance index and calibration plots. Histology was classified according to the Peritoneal Surface Oncology Group International (PSOGI). RESULTS: The derivation cohort included 95 patients, and the validation cohort 348. Five-year DFS rates were 51.5 and 62%, respectively. Cox regression analysis (derivation cohort) identified PSOGI histology of the peritoneal components, number of preoperative elevated tumor marker, and peritoneal disease extent, as assessed by peritoneal carcinomatosis index, to be predictors of DFS. The model's predictive capacity was higher than that of PSOGI classification alone, with respective concordance indexes of 0.702 ± 0.023 and 0.610 ± 0.018 (validation cohort). The nomogram approximated the perfect model in the calibration plots at 3- and 5-year DFS. CONCLUSIONS: An easy-to-use model that provides better prognostic stratification than histopathological features has been constructed. This nomogram may help clinicians in individualized survival predictions and informed clinical decision-making.

Defining stage in mucinous tumours of the appendix with peritoneal dissemination: the importance of grading terminology: systematic review.

BACKGROUND: Mucinous appendiceal neoplasms with peritoneal dissemination (PD) show a wide spectrum of clinical behaviour. Histological grade has been correlated with prognosis, but no universally accepted histological grading has been established. The aim of this systematic review was to provide historical insight to understand current grading classifications, basic histopathological features of each category, and to define which classification correlates best with prognosis. METHODS: MEDLINE and the Cochrane Library were searched for studies that reported survival across different pathological grades in patients with mucinous neoplasm of the appendix with PD treated with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy. PRISMA guidelines were followed. RESULTS: Thirty-eight studies were included. Ronnett's classification was the most common (9 studies). Classifications proposed by the Peritoneal Surface Oncology Group International (PSOGI) (6 studies) and the seventh or eighth edition of the AJCC (7 studies) are gaining in popularity. Nine studies supported a two-tier, 12 a three-tier, and two a four-tier classification system. Three studies demonstrated that acellular mucin had a better prognosis than low-grade pseudomyxoma peritonei in the PSOGI classification or M1bG1 in the eighth edition of the AJCC classification. Four studies demonstrated that the presence of signet ring cells was associated with a worse outcome than high-grade pseudomyxoma peritonei in the PSOGI classification and M1bG2 in the eighth edition of the AJCC. CONCLUSION: There is a great need for a common language in describing mucinous neoplasms of the appendix with PD. Evolution in terminology as a result of pathological insight turns the four-tiered PSOGI classification system into a coherent classification option.