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Endometrial cancer
2022-RA-450-ESGO Benefit of adjuvant radiotherapy depends on molecular class of early-stage endometrial cancer
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  1. Nanda Horeweg1,
  2. Remi A Nout2,
  3. Ellen Stelloo3,
  4. Ludy CHW Lutgens4,
  5. Jan J Jobsen5,
  6. Ina M Jürgenliemk-Schulz6,
  7. Elsbieta M van der Steen-Banasik7,
  8. Jan-Willem M Mens2,
  9. Annerie Slot8,
  10. Vincent THBM Smit3,
  11. Tjalling Bosse3 and
  12. Carien L Creutzberg1
  1. 1Radiation Oncology, Leiden University Medical Center, Leiden, Netherlands
  2. 2Radiotherapy, Erasmus MC Cancer Center, Rotterdam, Netherlands
  3. 3Pathology, Leiden University Medical Center, Leiden, Netherlands
  4. 4Maastricht Radiation Oncology Clinic, Maastricht, Netherlands
  5. 5Radiotherapy, Medisch Spectrum Twente, Enschede, Netherlands
  6. 6Radiation Oncology, University Medical Center Utrecht, Utrecht, Netherlands
  7. 7Radiotherapiegroep, Arnhem, Netherlands
  8. 8Radiotherapeutic Institute Friesland, Leeuwarden, Netherlands

Abstract

Introduction/Background The endometrial cancer (EC) molecular class is predictive for response to chemotherapy. Little is known about its’ predictive value for response to radiotherapy. We investigated benefit of adjuvant vaginal brachytherapy (VBT) and external beam radiotherapy (EBRT) across the four molecular classes.

Methodology Participants of the randomized PORTEC-1 (n=714) and PORTEC-2 (n=427) trials were eligible if their EC were molecularly profiled according to the WHO 2020 classification. PORTEC-1 included intermediate risk EC and compared EBRT to no adjuvant treatment. PORTEC-2 included high-intermediate risk EC and compared VBT to EBRT. Locoregional recurrence-free survival (LRFS) was estimated and compared using Kaplan-Meier’s methodology and log-rank tests. Correction for confounding by predefined clinicopathological factors was done using Cox proportional hazards models.

View this table:
Abstract 2022-RA-450-ESGO Table 1

Multivariable analysis of predictors of locoreginal recurrence-free survival

Abstract 2022-RA-450-ESGO Figure 1
Abstract 2022-RA-450-ESGO Figure 1

Results 881 patients with a median follow-up of 11.3 years were included. Patient and tumour characteristics are presented in table 1. EC were classified as POLE-mutant (POLEmut, 7.3%) mismatch-repair deficient (MMRd, 28.0%), p53-abnormal (p53abn, 9.1%) and non-specific molecular profile (NSMP, 55.6%). Overall, adjuvant radiotherapy significantly improved LRFS (figure 1A). In POLEmut EC no LR were observed (figure 1B). In MMRd EC, VBT and EBRT did not significantly improve LRFS (figure 1C). In p53abn EC, EBRT but not VBT significantly improved LRFS (figure 1D). In NSMP EC, both EBRT and VBT significantly improved LRFS. Adjuvant radiotherapy and molecular class retained significant impact on LRFS after correction for clinicopathological risk factors (table 1).

Conclusion Benefit of adjuvant radiotherapy in early-stage endometrioid EC differs between EC molecular classes. Omitting radiotherapy seems safe in early-stage POLEmut EC. Benefit of radiotherapy in MMRd EC is uncertain as only a small, non-significant reduction in LR was observed. In p53abn EC, EBRT significantly improved LRFS, in contrast to brachytherapy and no adjuvant treatment. NSMP EC seem to have a clear benefit of radiotherapy; VBT seems sufficient for locoregional tumour control.

https://doi.org/10.1136/ijgc-2022-ESGO.212

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