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PR002/#538  Synchronous endometrial and ovarian cancer (SEOC): refining pathological and molecular context to identify ‘low-risk SEOC’
  1. Amy Jamieson1,
  2. Jutta Huvila2,
  3. Samuel Leung3,
  4. Derek Chiu3,
  5. Mehrane Nazeran4,
  6. Amy Lum3,
  7. Janine Senz3,
  8. Michael Anglesio3,
  9. Blake Gilks4 and
  10. Jessica Mcalpine1
  1. 1University of British Columbia, Gynecologic Oncology, Vancouver, Canada
  2. 2University of Turku, Pathology, Turku, Finland
  3. 3University of British Columbia, Molecular Oncology, Vancouver, Canada
  4. 4University of British Columbia, Pathology, Vancouver, Canada

Abstract

Introduction Despite demonstration of the shared clonal origin of synchronous endometrial and ovarian cancers (SEOC), the definition of SEOC used in clinical practice has been inconsistent. Our aim was to determine if using the WHO2020-recommended/FIGO-2023-definition of stage IA3 SEOC could identify a clinically relevant biologically indolent subset of patients.

Methods Patients with stage IA3 SEOC, or with coexistent organ-confined endometrial and ovarian carcinomas were identified from a cohort of >2500 endometrial carcinomas (2001-2023), with clinicopathological, molecular, and outcome data compared.

Results Multiple differences were demonstrated between patients with stage IA3 SEOC (n=87) and those with coexistent organ-confined endometrial and ovarian carcinomas (n=85), (table 1). 65% of Stage IA3 SEOC were NSMP (10% POLEmut, 25% MMRd, no p53abn) and concordance with ovarian molecular subtype was high (94%). Improved progression-free survival for stage IA3 SEOC was observed (p=0.028)(figure 1) with only 6 (7%) recurrences and 3 (3%) deaths from disease recorded (vs. 20% and 8% in non-FIGO coexistent endometrial and ovarian carcinomas). Of the 6 Stage IA3 with an event (recurrence+/-death) all but one were NSMP (1MMRd), and no patients had L1CAM overexpression, or were ER negative.

Conclusion/Implications FIGO stage IA3 criteria defines a subset of low-risk SEOC that have a very indolent clinical course, behaving like Independent low-risk primary tumours and who are candidates for de-escalation of therapy. More work is needed to see if this low-risk SEOC definition can be safely expanded (e.g. inclusion of bilateral ovarian involvement, POLEmut high grade EC/OC or deep myoinvasion) or refined (e.g.,exclusion of low grade endometrioid p53abn, MMRd).

Abstract PR002/#538 Figure 1

Kaplan-Meier survival analysis demonstrating significantly improved progression-free survival in WHO-2020/FIGO-2023 criteria (stage IA3) synchronous endometrial and ovarian cancers

Abstract PR002/#538 Table 1

Clinicopathological and molecular characteristics and outcomes of the total cohort of endometrial and ovarian carcinomas comparing those defined by co-existent endometrial and ovarian-confined disease vs. FIGO-2023 criteria (stage IA3). Note: pathologic/molecular parameters are given for the endometrial carcinoma

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