Dostarlimab plus chemotherapy sustained durable disease control in dMMR/MSI-H primary advanced or recurrent endometrial cancer in the phase 3 RUBY trial, with updated abstract data ahead of ASCO 2026. At a median follow-up of 55.6 months, mixture cure modeling estimated that 54% of patients had curative potential based on progression-free survival patterns. The 4-year PFS rates favored dostarlimab—57.9% versus 15.7% with chemotherapy alone—while the overall survival analysis also showed an advantage for the combination, with the median OS reported as 44.6 months versus 28.2 months. Only a small number of new PFS events were added since the prior analysis, suggesting the durability signal is holding. The updated readout strengthens the evidence base for immune checkpoint inhibition in a biomarker-defined setting, where durability and long-term control are often decisive for clinical adoption.