Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2026

Sustained remission and long-term survival outcomes with dostarlimab plus chemotherapy in patients with dMMR/MSI-H primary advanced or recurrent endometrial cancer in the ENGOT-EN6-NSGO/GOG-3031/RUBY trial (Encore) (145985)

Vladyslav Sukhin 1 , Thomas Herzog 2 , Lucy Gilbert 3 , Anthoula Koliadi 4 , Cara Mathews 5 , Sarah E Gill 6 , Graziana Ronzino 7 , Iwona Podzielinski 8 , Stefan Kommoss 9 , Mitchell I Edelson 10 , Anna M Thijs 11 , Robert W Holloway 12 , Bradley Monk 13 , Eirwen M Miller 14 , Tashanna Myers 15 , John P Diaz 16 , Melissa MJ Farnham 17 , Bharat Patel 18 , Laura Austin 19 , Trine Nøttrup 20 , Matthew A Powell 21
  1. Grigoriev Institute for Medical Radiology and Oncology National Academy of Medical Sciences of Ukraine, Kharkiv, Ukraine
  2. University of Cincinnati Cancer Center; Department of Obstetrics & Gynecology, College of Medicine, Cincinnati, OH, USA
  3. Division of Gynecologic Oncology, Research Institute, McGill University Health Centre, Gerald Bronfman Department of Oncology, McGill University, Montreal, Quebec, Canada
  4. Department of Gynecologic Oncology, Uppsala University Hospital, and Nordic Society of Gynecologic Oncology (NGSO), Uppsala, Sweden
  5. Womens and Infants Hospital, Legorreta Cancer Center, Alpert Medical School of Brown University, Providence, RI, USA
  6. St Joseph’s/Candler Gynecologic Oncology & Surgical Specialists, Candler Hospital, Savannah, GA, USA
  7. Department of Oncology, Ospedale Vito Fazzi, Lecce, Italy
  8. Department of Gynecologic Oncology, Parkview Health, Fort Wayne, IN, USA
  9. Department of Gynecology and Obstetrics, Diak Klinikum, Landkreis Schwäbisch Hall, Schwäbisch Hall, Germany
  10. Hanjani Institute for Gynecologic Oncology, Jefferson Abington Hospital, Willow Grove, PA, USA
  11. Department of Medical Oncology, Catharina Hospital, Eindhoven, The Netherlands
  12. AdventHealth Cancer Institute, Orlando, FL, USA
  13. GOG Foundation, Philadelphia, PA, USA, and Florida Cancer Specialists and Research Institute, West Palm Beach, FL, USA
  14. Division of Gynecologic Oncology, Western Pennsylvania Hospital, Allegheny Health Network, Pittsburgh, PA, USA
  15. Baystate Medical Center, Springfield, MA, USA
  16. Miami Cancer Institute at Baptist Health South Florida, Miami, FL, USA
  17. GSK, Melbourne, Australia
  18. GSK, London, UK
  19. GSK, Collegeville, PA, USA
  20. Department of Oncology, Copenhagen University Hospital – Rigshospitalet and NSGO, Copenhagen, Denmark
  21. Washington University School of Medicine, Siteman Cancer Center, St Louis, MO, USA

Background: Dostarlimab (DOST) + carboplatin-paclitaxel (CP) demonstrated significant progression-free survival (PFS) and overall survival (OS) benefits in patients with mismatch repair–deficient/high microsatellite instability (dMMR/MSI-H) primary advanced or recurrent endometrial cancer (EC) in the RUBY trial (NCT03981796). Here, we report updated efficacy with 4 years of follow-up in patients with dMMR/MSI-H EC and characteristics of patients with long-term disease control.

Methods: Patients were randomized (1:1) to receive DOST+CP or placebo (PBO)+CP every 3 weeks (6 cycles) followed by DOST or PBO monotherapy every 6 weeks for up to 3 years or until disease progression. Descriptive analyses of PFS and OS were conducted. In this post hoc analysis, for patients treated with DOST+CP who achieved complete response (CR) or long-term (≥3 years) disease control, clinical characteristics, treatment duration, and RECIST v1.1 responses (CR/partial response [PR]/stable disease [SD]) were reported at 1 year landmark intervals. Funding: GSK

Results: Overall, 53 patients were treated with DOST+CP and 65 received PBO+CP. Median follow-up: 55.6 months. DOST+CP vs PBO+CP demonstrated sustained OS (hazard ratio [HR] 0.34, 95% CI 0.19–0.63; 4-year OS rate: 72.8% vs 40.3%) and PFS (HR 0.30; 95% CI, 0.17–0.52; 4-year PFS rate: 57.9% vs 15.7%) benefits. Median PFS and OS in the DOST+CP arm were not reached. Only 4 new progression events occurred within 2.5 years after the primary PFS analysis (23/09/2022). Of patients treated with DOST+CP, 17 achieved CR, of whom few progressed (3/17) or died (1/17). Only 1/12 patients with CR at 1 year had progression at 4 years. Sustained clinical benefit was observed across disease responses (CR/PR/SD).

Conclusion: The high rate of durable remission suggests the potential for long-term management and disease control with DOST+CP in this patient population.

Previously presented at ESMO Gynaecological Cancer 2026, FPN:71R0, Vladyslav Sukhin et al. Reused with permission.