REal Word aPpLicAtion of Molecular Based Endometrial Cancer Classification

Overview

Despite the high incidence, endometrial cancer represents a low mortality neoplasma due to the high prevalence of early-stage diagnosis (90%). Concerning the uterine-confined disease (FIGO 2009 and 2023 stage I-II), molecular-based classification has showed an unprecedent impact on the treatment algorithm leading to a full integration into the latest staging classification. The first evidence of the prognostic value of molecular subgroups came from the TCGA data in which patients were subdivided into: patients with POLE gene alterations, MMR deficient (MMRd), patients with TP53 gene mutations, absence of one of these alterations (NSMP). The use of molecular classification reveals distinct prognostic groups ranging from an excellent prognosis (POLE mutated) to those with a worst prognosis (p53 mutated). Therefore, according to the ESGO guidelines, in patients with stage I-II POLE mutated endometrial cancer, the recurrence rate is so low as to justify omitting adjuvant treatment in favor of observation alone. Several groups have applied a diagnostic algorithm using five immunohistochemical markers (p53, MLH1, MSH2, MSH6 and PMS2) and a molecular test (analysis of mutations in the exonuclease domain of POLE) to identify prognostic groups similar to the molecular classification of TCGA. The feasibility of this approach has been confirmed by many publications that have all consistently reported prognostic relevance especially in high-grade and high-risk tumours in several independent cohorts and prospective clinical trials. In conclusion, despite the validation of immunohistochemical evaluation in place of molecular evaluation, the need to perform a more complex evaluation to define POLE status makes its implementation not yet ubiquitous. The integration of molecular analysis of the POLE mutations remains challenging across the centers involved in the management of endometrial cancer. REPLACE is a national, cross-sectional survey that will census all Italian gynaecology centres (≈ 264) involved in the endometrial cancer treatment into: (i) quantify POLE testing adoption, (ii) describe diagnostic methodologies, (iii) map treatment de-escalation strategies triggered by POLE status, and (iv) explore management pathways where POLE is unavailable. Findings will highlight implementation gaps and inform future network initiatives.

Endometrial carcinoma is the most common gynecological cancer in Europe, with an incidence of 420.368 new cases in 2022 and a low mortality (97.300) due to a high prevalence (90%) of early stage at diagnosis. In 2013, the TCGA succeeded in defining 4 molecular subgroups (POLE mutated patients, high microsatellite instability \[MSI-H\], TP53 mutated patients or none of these alterations) significantly associated with prognosis. In particular, patients with POLEmut tumors demonstrate an excellent prognosis, while those with mutations in TP53 exhibit a poorer prognosis. Endometrial carcinomas with MSI-H fall within an intermediate prognostic range. Based on this data, different groups developed and validated a pragmatic molecular classifier leveraging surrogate immunohistochemistry markers (p53, MLH1, MSH2, MSH6 and PMS2) identifying prognostic groups analogous to the TCGA molecular-based classification. The feasibility of this approach was confirmed by a large number of publications that have all consistently reported prognostic relevance particularly in high-grade and high-risk tumors in several independent cohorts and prospective clinical trials. Overall, a growing body of evidence had been generated, supporting the role of molecular features in understanding disease behavior, ultimately influencing staging and therapeutic decisions. Consequently, this led to the full integration of molecular data into the latest FIGO staging system and ESMO 2022 and ESGO 2025 guidelines. Despite the absence of prospective randomized trials, the recurrence rate of patients with stage I-II POLE mutated endometrial cancer has been shown to be so low that omitting adjuvant treatment in favor of observation alone can be justified. This concept has been even strongly highlighted in the last endometrial cancer staging system, where uterine-confined POLE mutated cases are downstaged to IAmPOLEmut regardless of the presence of any other known prognostic indicator (es. Lymphovascolar space involvement, grading 3, non-endometrioid histotype). All markers are required to be assessed to define molecular subgroups since a combination of positive tests can occur in approximatively 5% of all carcinomas (so-called 'multiple classifiers'); however, among them, POLE evaluation remains the only one requiring DNA sequencing, posing a significant challenge for many centers. In particular, only pathogenic variants of POLE identified in the gene's exonuclease domain can currently define POLE mutant cases. In addition to the barriers faced in POLE testing, many concerns have emerged regarding tailoring staging and therapeutic algorithms in the absence of randomized clinical trials. The overall low incidence of POLE mutant cases, and the even lower association with well-recognized negative prognostic features (such as non-endometrioid histotype, lymphovascular space involvement, and MELF pattern) have further contributed to uncertainties regarding the optimal clinical management of these patients. Despite guideline endorsement, POLE sequencing is technically demanding and not uniformly available. Italy's hub-and-spoke cancer model assigns complex care to I and II levels centres; however, no national data describe POLE testing availability or its impact on therapeutical choices. Understanding current practice is a prerequisite to standardize molecularly driven care and to design interventional trials. The primary objective is to determine the proportion of Italian gynaecology units that perform routine POLE testing in endometrial cancer surgical specimens. This is a nation-wide, cross-sectional, web-based survey of Italian first or second level gynaecology units, coordinated by Fondazione Policlinico Universitario Agostino Gemelli IRCCS. Each partecipant centre will nominate one senior clinician (≥ 5 years EC experience) to complete the questionnaire once. The study, in the form of a survey, aims to ask participating centres a questionnaire with multiple-choice questions. In case of adherence to survey participation, the identified referent clinician is required to answer the questionnaire within 1 month of submission; otherwise, a reminder will be sent. Subsequently, the answers will be centralized by the promoting centre, which will assess the appropriateness and quality of the data provided. The answers will also be subjected to a blind review procedure by an external reviewer. The maximum duration of the study, calculated as the time interval from survey approval to data collection, is estimated to be one year. The survey aims to provide an insight of the application of molecular classification in endometrial cancer, particularly POLE evaluation, in experted centres for this pathology. It is expected that the questionnaire format and the blinded review will provide interesting data regarding possible problems and/or controversies of molecular driven treatment application in clinical practice.