Dostarlimab plus chemotherapy showed durable disease control in dMMR/MSI-H endometrial cancer, with updated RUBY trial data released ahead of ASCO 2026. At a median follow-up of 55.6 months, 4-year progression-free survival was 57.9% with dostarlimab versus 15.7% with chemotherapy alone, and mixture cure modeling estimated 54% of patients with curative potential. In parallel, TROPION-Breast02 results supported another ADC push into breast cancer earlier lines: the FDA approval described in the same period was based on an OS improvement for datopotamab deruxtecan in a metastatic setting for patients not eligible for PD-1/PD-L1 inhibitors. The combination of long follow-up in endometrial cancer and continued OS signals for ADCs highlights how immunotherapy- and target-driven regimens are competing for earlier standard-of-care positioning. For clinicians and developers, the common thread is durability and statistical separation—outcomes now being framed not only by response rates but by longer-term endpoints like OS and sustained PFS, particularly in biomarker-defined cohorts.