Abstract
Patients with early-stage endometrial cancer are frequently treated with surgery and radiotherapy or chemotherapy, for which 5-year survival rates approach 95%; conversely, the outcomes for patients with advanced or recurrent endometrial cancer are more inauspicious. Fortunately, the advent of immunotherapy, combined with chemotherapy, has conferred improved survival, especially in endometrial cancer patients with a mismatch repair deficiency (dMMR). We conducted an extensive PubMed search on the topics of endometrial cancer and immunotherapy treatment. The combination of dostarlimab and chemotherapy reportedly coincides with a 2-year progression-free survival (PFS) of 61% compared to a 12-month PFS of 74% for pembrolizumab. Moreover, the follow-up data for dostarlimab extended beyond 44 months and the median overall survival (OS) has not been reached compared to more limited OS data for both pembrolizumab and durvalumab; additionally, dostarlimab’s pronounced risk of disease progression or death in both dMMR (70%) and mismatch repair–proficient (pMMR) (46%) patients is considerable. While pembrolizumab, dostarlimab and durvalumab with chemotherapy are associated with beneficial outcomes in advanced-stage or recurrent endometrial cancer, dostarlimab has distinguished itself with unsurpassed survival data compared to pembrolizumab and durvalumab.
Introduction
Endometrial cancer is the most common neoplasm affecting the female genital tract in the United States, accounting for 67,880 newly diagnosed cases and 13,250 patient deaths in 2024 (1). Historically, the standard of care for advanced-stage or high-risk endometrial cancer was chemotherapy and/or radiotherapy (2). When considering chemotherapy, standard of care regimens frequently encompass carboplatin and paclitaxel (3). Nonetheless, patients with advanced-stage or recurrent endometrial cancer frequently relapse and 5-year survival rates are reportedly 20% (4).
Since endometrial cancer is considered a highly immunogenic disease (i.e., the malignancy coincides with the presence of tumor-associated antigens), immunotherapy has been studied as a single-agent treatment or in combination with chemotherapy for advanced-stage or recurrent endometrial cancer (5-8). The mismatch repair–deficient (dMMR) classification, encompassing approximately 36% of endometrial cancer patients (7), is associated with a more inauspicious prognosis; opportunely, these tumors are especially amenable to the effects of immunotherapy (9, 10).
When considering mismatch repair–proficient (pMMR) patients, the clinical outcomes with immunotherapy (e.g., pembrolizumab and dostarlimab) coincide with only moderate clinical benefits compared to chemotherapy alone (11-13). Hence, to enhance patient survival rates, both dMMR and pMMR endometrial cancer studies have further incorporated chemotherapy with immunotherapy (6, 14, 15).
Immunotherapy Mechanism of Action
Tumor-infiltrating lymphocytes and T-cell activation in response to antigens are a function of the adaptive immune system (16). Nevertheless, immune interactions can be impeded when neoplastic cells develop either unrecognizable or undetected surface proteins (17, 18). Accordingly, with the addition of immune checkpoint inhibitors (ICIs), the immune system is bolstered, thereby disrupting the capacity for these proteins to conceal themselves from the T-cells to which they are vulnerable (19). Dostarlimab, pembrolizumab and durvalumab are currently approved ICIs in the treatment of advanced or recurrent endometrial cancer, albeit under different clinical scenarios.
Dostarlimab. Dostarlimab, a monoclonal antibody (mAb) that targets programmed cell death (PD-1), was initially studied as a single-agent therapy for endometrial cancer in the Phase 1 Garnet study (13), wherein response rates of 45.5% and 15.4% for dMMR/microsatellite high (MSI-H) and pMMR/microsatellite stable (MSS) were observed, respectively.
In the phase 3 RUBY trial (5), advanced or recurrent endometrial cancer patients (n=494), 23.9% of whom were dMMR, received dostarlimab (500 mg), carboplatin (AUC 5), and paclitaxel (175 mg/m2) for 6 cycles of induction therapy, followed by dostarlimab (1,000 mg) maintenance therapy or chemotherapy alone. In the dMMR group, progression-free survival (PFS) at 24 months was 61.4% [95% confidence interval (CI)=46.3-73.4] for the dostarlimab patients vs. 15.7% (95% CI=7.2-27.0) in the chemotherapy-alone group [hazard ratio (HR) for progression or death=0.28; 95% CI=0.16-0.50; p<0.001] (Table I). This benefit extended to overall survival (OS); median OS for dostarlimab and chemo was not estimable (NE) (95% CI=NE-NE) compared to 31.4 months (95% CI=20.3-NE) in the chemo-alone group (HR=0.32; 95% CI=0.17-0.63).
Progression-free survival and overall survival data with dostarlimab, pembrolizumab and durvalumab coupled with chemotherapy in dMMR endometrial cancer.
When considering the pMMR patients, dostarlimab plus chemotherapy exhibited a clinically improved PFS (14.3 months vs. 8.3 months) benefit compared to the chemotherapy-alone group (HR=0.63; 95% CI=0.44–0.91) (Table II). Moreover, OS was 34.0 months (95% CI=28.6-NE) with dostarlimab and chemo vs. 27.0 months (95% CI=21.5-35.6) for the chemotherapy-alone group (HR=0.79; 95% CI=0.60-1.04).
Progression-free survival and overall survival data with dostarlimab, pembrolizumab and durvalumab coupled with chemotherapy in pMMR endometrial cancer.
In the overall population, a statistically significant OS improvement was observed in the dostarlimab arm [median OS of 44.6 months (95% CI=32.6-NR) compared to the chemotherapy-alone group (28.2 months, 95% CI=22.1-35.6; HR=0.69, 95% CI=0.54-0.89)]; 1-sided p-value=0.002) (14). Consequently, the combination of dostarlimab with paclitaxel and carboplatin was approved for the treatment of dMMR or MSI-H primary advanced or recurrent endometrial cancer in July 2023 and in August 2024, the approval was expanded to include pMMR or microsatellite stability (MSS) patients.
Pembrolizumab. Pembrolizumab and lenvatinib were studied in first-line advanced or recurrent endometrial cancer patients with pMMR disease, not to mention patients who relapsed on chemotherapy-alone, but OS improvements were not borne out with this therapeutic combination (15, 20). The NRG-GY018 study evaluated the use of pembrolizumab (200 mg) with carboplatin (AUC 5) and paclitaxel (175 mg/m2) compared to chemotherapy alone in both advanced stage (stage III or IVA) or stage IVB or recurrent endometrial cancer with either dMMR or pMMR disease (6). The PFS at 12 months was 74% for the dMMR group treated with pembrolizumab and chemotherapy, compared to 38% in the chemotherapy-alone group (HR for progression or death=0.30; 95% CI=0.19-0.48; p<0.001); median OS was NR for both groups (HR=0.55; 95% CI=0.25-1.19; p=0.0617) (21).
The PFS for the pMMR patients treated with pembrolizumab and chemotherapy was 13.1 months and 8.7 months for the chemotherapy-alone group (HR=0.54; 95% CI=0.41-0.71; p<0.001). The median OS was 27.96 months (95% CI=21.42-NR) in the pembrolizumab group vs. 27.37 months (95% CI=19.52-NR) in the chemotherapy-alone group (HR=0.79; 95% CI=0.53-1.17; p=0.1157). Consequently, pembrolizumab together with chemotherapy was approved for the treatment of advanced stage or recurrent endometrial cancer in June 2024, regardless of MMR status.
Durvalumab. In the Phase 3 DUO-E trial, advanced or recurrent endometrial cancer patients were assigned to receive carboplatin (AUC 5 or 6), paclitaxel (175 mg/m2) and durvalumab (1,500 mg), carboplatin, paclitaxel and durvalumab, followed by maintenance therapy with either placebo, durvalumab-alone, or durvalumab and olaparib (22). There was a statistically significant PFS benefit ascribed to the dMMR patients (n=95) treated with durvalumab and chemotherapy [median PFS was NR (95% CI=NR-NR)], compared to 7 months for the chemotherapy-alone group (95% CI=6.7-14.8; HR=0.42, 95% CI=0.22-0.80); in the durvalumab/olaparib group, the PFS was 31.8 months (HR=0.41) compared to chemotherapy alone. Additional subgroup analyses illustrated an improved PFS benefit in the dMMR patients who underwent durvalumab maintenance therapy compared to chemotherapy alone (HR=0.42, 95% CI=0.22-0.80) and durvalumab and olaparib maintenance therapy vs. chemotherapy alone (HR=0.41, 95% CI=0.21 to 0.75).
In the pMMR group, durvalumab and chemo exhibited a PFS benefit compared to chemotherapy alone (HR=0.77, 95% CI=0.60-0.97); moreover, the reported HR for durvalumab and chemotherapy compared to chemotherapy alone was 0.77 (95% CI=0.60-0.97) and 0.57 (95% CI=0.44-0.73) for durvalumab and chemotherapy, followed by durvalumab and olaparib. In June 2024, the FDA approved durvalumab with carboplatin plus paclitaxel for primary advanced or recurrent endometrial cancer patients who are dMMR.
Toxicity. The most frequently encountered adverse events (AEs) observed with durvalumab and chemotherapy include anemia, neutropenia, nausea, fatigue, alopecia, and constipation, as well as high-grade hypothyroidism and hepatic AEs (23). Adverse events leading to treatment modifications occurred in 54.5% of patients and treatment discontinuations were observed in 20.9% of subjects, some of which were ascribed to immune-mediated pneumonitis. When considering the DUO-E trial, durvalumab alone or with olaparib maintenance therapy continued until patients experienced toxicity or disease progression, compared to a prescribed treatment duration (22); hence the prolonged treatment may have engendered greater toxicity despite the increased survival benefit.
Dostarlimab primarily effectuates diarrhea, fatigue, and nausea, of which grade 1 or 2 was most frequently encountered (13). Additionally, immune-related AEs (e.g., hypothyroidism, arthralgia) were also observed. Dostarlimab was associated with a higher incidence of dose reductions (70.9%) and a reported discontinuation rate of 17.4% (5). Similarly, pembrolizumab and chemotherapy are commonly associated with fatigue, gastrointestinal issues, neutropenia, elevated liver enzymes and immune-related AEs (e.g., pneumonitis, endocrinopathy). Serious AEs occurred in 35% of patients receiving pembrolizumab, to which a 14% discontinuation rate was ascribed (6). Accordingly, since immune-mediated conditions can manifest themselves in response to immunotherapy, relevant monitoring and treatment protocols should be instituted to avert this event (23).
Discussion
The primary management of advanced-stage or recurrent endometrial cancer has significantly improved outcomes, particularly with the introduction of dostarlimab, pembrolizumab and durvalumab; atezolizumab is also being evaluated as a potential therapy in the management of this disease (24). Nevertheless, the clinical improvements ascribed to these agents vary, obscuring the selection of a predetermined therapy from which a patient might derive the greatest benefit.
When considering dMMR endometrial cancer, pembrolizumab, dostarlimab and durvalumab have exhibited compelling PFS data. However, the use of dostarlimab reportedly coincides with a 2-year PFS of 61% compared to a 12-month PFS of 74% for pembrolizumab (4, 14). The follow-up in the dostarlimab study extended beyond 44 months, and the median OS was not yet reached, not to mention there was a reduced risk of disease progression or death in both dMMR (70%) and pMMR (46%) patients (14). One may also surmise that the efficacy data from the phase 3 ruby trial were even more pronounced because of the study’s inclusion of uterine carcinosarcoma, an extremely aggressive endometrial cancer subtype. Conversely, in the DUO-E trial, olaparib putatively improved PFS although the independent benefit is indeterminate (22). We further acknowledge the limitations inherent to indirect, cross-trial comparisons; and despite the OS advantages with dostarlimab, the OS is based on non-reached medians with limited follow-up in some subgroups. A more balanced appraisal should include critical examination of the evidence for all agents, including potential limitations, toxicities, and real-world applicability.
Conclusion
Immunotherapy and chemotherapy have substantially engendered improved patient outcomes in advanced or recurrent endometrial cancer, irrespective of mismatch repair status. Moreover, the tolerability profiles inherent to dostarlimab, pembrolizumab and durvalumab are reasonable and presumably do not inordinately exacerbate the toxicities inherent to chemotherapy (5, 6, 25). Ultimately, when considering the aforesaid immunotherapy agents, the combination of dostarlimab and chemotherapy has a longer duration of follow-up in both dMMR and pMMR patients compared to pembrolizumab and dostarlimab. While essaying to further delineate appropriate management, we further recognize that clinical judgement should also incorporate a patient’s medical history, mutational status, and quality of life.
Footnotes
Authors’ Contributions
John Micha: conceptualization, supervision, original draft preparation- final manuscript review. Randy Bohart: content review, draft preparation- final manuscript review. Joshua Gorman: data acquisition, data review-manuscript preparation and review. Bram Goldstein: study supervision, original draft preparation, draft preparation- final review and editing of the manuscript.
Conflicts of Interest
The Authors declare no potential conflicts of interest relevant to this article.
Funding
This study was supported by the Women’s Cancer Research Foundation.
Artificial Intelligence (AI) Disclosure
No artificial intelligence (AI) tools, including large language models or machine learning software, were used in the preparation, analysis, or presentation of this manuscript.
- Received April 21, 2025.
- Revision received May 15, 2025.
- Accepted May 22, 2025.
- Copyright © 2025 The Author(s). Published by the International Institute of Anticancer Research.
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY-NC-ND) 4.0 international license (https://creativecommons.org/licenses/by-nc-nd/4.0).