731P - Post-progression survival outcomes in patients (pts) with primary advanced or recurrent endometrial cancer (pA/rEC) in the ENGOT-EN6-NSGO/GOG-3031/RUBY trial who received follow-up immunotherapy

Background

In Part 1 of the phase 3 ENGOT-EN6-NSGO/GOG-3031/RUBY trial (NCT03981796), dostarlimab+carboplatin-paclitaxel (DOST+CP) significantly improved PFS (HR 0.64) and OS (HR 0.69) vs placebo (PBO)+CP in the overall population of pts with pA/rEC. Limited data are available on outcomes with follow-up anticancer treatment (FUACT) after DOST+CP. Here we report post-progression survival outcomes of pts in the overall and mismatch repair proficient/microsatellite stable (MMRp/MSS) populations who received FUACT of immunotherapy (IO).

Methods

Pts were randomized 1:1 to receive DOST/PBO+CP Q3W (6 cycles) followed by DOST/PBO monotherapy Q6W for ≤3 years. At interim analysis 2 (37.2 mo of follow-up), updated post hoc analyses of OS adjusted for treatment switching via rank-preserving structural failure time (RPSFT) were performed in the overall and MMRp/MSS populations of pts who received FUACT of IO and for pts receiving pembrolizumab-lenvatinib (PEM-LEN) in the MMRp/MSS population.

Results

In total, 494 pts were randomized (table). FUACT of IO was received by 137 and 102 pts in the overall and MMRp/MSS populations, respectively; PEM-LEN was received by 65 pts in the MMRp/MSS population. Approximately twice as many patients received FUACT of IO in the PBO+CP vs DOST+CP arm. When adjusted for subsequent IO, RPSFT analyses showed HRs of 0.63 (overall) and 0.76 (MMRp/MSS) for DOST+CP vs PBO+CP, consistent with the unadjusted HRs for OS in the primary analysis. In the MMRp/MSS population receiving subsequent PEM-LEN, HR of RPSFT-adjusted OS was also consistent at 0.77.

Table: 731P

aImmunotherapies: PEM, PEM-LEN, PEM-tamoxifen, DOST, retifanlimab/epacadostat, durvalumab combinations, investigational product, atezolizumab combinations, bevacizumab/atezolizumab, MK7694A, and nivolumab combinations.

bDOST+CP increases survival by acceleration factor (AF).

Conclusions

Adjusted OS using RPSFT for subsequent use of IO in the overall and MMRp/MSS populations, including PEM-LEN in the MMRp/MSS population, showed limited impact on survival benefits, supporting frontline use of dostarlimab+CP as standard of care in all pts with pA/rEC.

Clinical trial identification

NCT03981796.

Editorial acknowledgement

Writing and editorial support, funded and coordinated by GSK, was provided by Shannon Morgan-Pelosi, PhD, CMPP, and editor TBD, of Ashfield MedComms, an Inizio company.

Legal entity responsible for the study

GSK.

Funding

GSK.

Disclosure

M.R. Mirza: Financial Interests, Personal, Speaker, Consultant, Advisor: AstraZeneca, Biocad, GSK, Karyopharm, Merck, Roche, Zailab; Financial Interests, Institutional, Research Funding: Apexigen, AstraZeneca, Deciphera (trial chair), GSK, Ultimovacs; Financial Interests, Personal, Stocks/Shares: Karyopharm ; Financial Interests, Personal, Member of Board of Directors: Karyopharm. C. Mathews: Financial Interests, Institutional, Research Grant: Astellas, AstraZeneca, Deciphera, Moderna, GSK, Regeneron, Seattle Genetics; Financial Interests, Personal, Advisory Board: IMAB biopharma. L. Gilbert: Financial Interests, Institutional, Advisory Board: Alkermes, AstraZeneca, Clovis, Corcept Therapeutics, Esperas, GOG Foundation, GSK, ImmunoGen, IMV, K-Group Beta, Karyopharm, Merck Sharp & Dohme, Mersana Therapeutics, Novocure GmbH, OncoQuest Pharmaceuticals, Roche, Shuttuck Labs, Sutro BioPharma Inc, Tesaro; Financial Interests, Personal, Speaker, Consultant, Advisor: GSK, Merck; Financial Interests, Personal, Other, honoraria: CanariaBio, Eisai, Eisai-Merck, GOG Foundation, GSK, ImmunoGen, Kora Healthcare, Merck; Financial Interests, Personal, Other, travel support: EndomEra, GOG Foundation, GSK, Merck, Zentalis; Financial Interests, Personal, Other, participation on a Data Safety Monitoring Board: CanariaBio, Eisai, Eisai-Merck, GOG Foundation, GSK, ImmunoGen, Kora Healthcare, Merck. L. Bjorge: Financial Interests, Personal, Speaker, Consultant, Advisor: GSK. M.A. Powell: Financial Interests, Personal, Speaker, Consultant, Advisor: AstraZeneca, Clovis Oncology, Eisai, GSK, Merck, Seagen, Tesaro. T. Van Gorp: Financial Interests, Institutional, Research Funding: Amgen, AstraZeneca, Roche; Financial Interests, Institutional, Speaker, Consultant, Advisor: AbbVie, AstraZeneca, BioNTech, Cancer Communications and Consultancy Ltd, Eisai, GSK, ImmunoGen, Inc., Incyte, Karyopharm, MSD/Merck & Co., OncXerna Therapeutics, Seagen, Tubulis, Zentalis; Financial Interests, Institutional, Other, Support for attending meetings and/or travel: AstraZeneca, ImmunoGen, Inc., MSD/Merck, PharmaMar; Financial Interests, Personal, Non remunerated activity, Chair: Belgian and Luxembourg Gynaecological Oncology Group. D. Bender: Financial Interests, Institutional, Other, grants: AbbVie, AstraZeneca, Clovis Oncology Inc, Genentech, MSD, Tesaro. G. Canturia: Financial Interests, Personal, Speaker, Consultant, Advisor: GSK; Other, Personal, Other, patent on an anti-tumor lipid molecule that is early stage of development: TBD. R. Gogoi: Non-Financial Interests, Personal, Advisory Board, or data safety monitoring board: Pionyr Pharmaceuticals; Financial Interests, Personal, Other, receipt of equipment, materials, drugs, medical writing, gifts or other services: Bausch + Lomb. G. Antony: Financial Interests, Personal, Full or part-time Employment: GSK. S. Stevens: Financial Interests, Personal, Full or part-time Employment: GSK. G. Valabrega: Financial Interests, Personal, Speaker, Consultant, Advisor: GSK; Financial Interests, Personal, Other, honoraria: AstraZeneca, GSK, MSD; Financial Interests, Personal, Other, travel support: AstraZeneca, PharmaMar; Non-Financial Interests, Personal, Advisory Board: AstraZeneca, EISAI, GSK, MSD. All other authors have declared no conflicts of interest.