Presentations at the Society for Gynecologic Oncology (SGO) 2026 Annual Meeting on Women’s Cancer add important context to the growing use of immunotherapy for advanced and recurrent endometrial cancer. Pamela T. Soliman, MD, MPH, reviews the long-term outcomes from the RUBY trial, real-world experience with dostarlimab, and the need for a more biomarker-guided approach to upfront care.

Following these presentations, featured expert Pamela T. Soliman, MD, MPH, was interviewed by Conference Reporter Medical Director Lauren Weinand, MD. Clinical perspectives from Dr Soliman on these findings are presented here.

Over the past several years, since the initial data from part 1 of the RUBY trial and the KEYNOTE-868 study were presented at the SGO 2023 Annual Meeting on Women’s Cancer, the whole landscape for the upfront treatment of endometrial cancer has changed. The data from these studies were extremely promising in patients with mismatch repair–deficient (dMMR) tumors. I think that most gynecologic oncologists treating patients with advanced endometrial cancer understand that if a patient has a dMMR tumor and advanced disease at diagnosis, they will likely respond well to chemotherapy plus an ICI.

Anytime we see promising early data, it is important not to lose sight of the long-term outcomes (ie, whether the benefits are sustainable, what the toxicity profile is, and how patients are impacted long-term). At the recent SGO 2026 Annual Meeting on Women’s Cancer, Matthew A. Powell, MD, presented the 4-year survival outcomes from the RUBY trial (abstract 143). Part 1 of the RUBY trial was a phase 3 randomized study in primary advanced or recurrent endometrial cancer in which patients received carboplatin and paclitaxel plus dostarlimab or carboplatin and paclitaxel plus placebo. From this initial analysis, which was presented at SGO 2023 as previously noted, we know that in the dMMR/microsatellite instability–high (MSI-H) population, dostarlimab improved progression free survival by approximately 72%; the overall survival data were still being matured at that time.

At this year’s SGO meeting, researchers reported the analysis on the patients from RUBY who received dostarlimab or placebo maintenance for up to 3 years or until disease progression, with a median follow-up of 55.6 months. Consistent with the initial early data, there was a 66% reduction in risk of death with dostarlimab vs placebo, which is obviously a huge impact on survival, even over the long-term.

At this point in the study, many of the patients had completed their maintenance therapy and were potentially off treatment, so another question is: Are these benefits sustainable even after maintenance therapy is completed? Patients who were alive and progression free at 1 year had almost a 97% probability of remaining progression free up to 3 years. Thus, an early response can be a predictor of long-term response, which is really what we want to see. Are we potentially curing more patients by adding immunotherapy up front? I do not think we know that yet, but these data are pretty promising.

You may see findings from clinical trials that can change practice. However, it is important to keep in mind that for most trials, the patient population is carefully selected and may have fewer comorbidities or a higher performance status. So, sometimes, once drugs are approved by the US Food and Drug Administration (FDA), you may not see the same level of outcomes in the real world, which is where real-world analyses can be useful.

A real-world retrospective analysis by John Nakayama, MD, and colleagues of first-line systemic treatment with dostarlimab plus chemotherapy in patients with advanced or recurrent endometrial cancer was also presented at the SGO 2026 Annual Meeting on Women’s Cancer (poster 1156). This study was important because the data were consistent with the results from the RUBY trial, but it is still early to look at long-term impacts from this real-world analysis.

The decision regarding which patients should receive immunotherapy up front is not always straightforward. In clinical practice, for patients who have a dMMR or an MSI-H tumor, it is a no-brainer. Data across studies have demonstrated that adding an ICI to chemotherapy in patients with advanced disease results in a consistent reduction in recurrence risk, and then we saw the RUBY 4-year data at SGO 2026 showing a long-term survival benefit.

Regarding patients with mismatch repair-proficient (pMMR) tumors, I think that there are probably subgroups that benefit from immunotherapy, but I do not give immunotherapy to all patients with advanced endometrial cancer because I am not convinced that it will benefit everybody. To commit a patient with pMMR disease to 2 or 3 years of immunotherapy without really knowing that it will benefit that individual is hard for me to do. I discuss it with the patient, but I do not necessarily recommend it for everyone with pMMR tumors.

I think that we are learning more and more that biomarkers can play a significant role in how we treat patients in the recurrent setting, but that is probably going to be true for the upfront setting as well. More people are getting biomarker testing done sooner and are not waiting for recurrence. And, as more data and drugs become available, there is even more reason to do the testing. If it is something you can take action on, that is ultimately what is going to convince people that it is meaningful.