Following the Keynote B21 trial, clinicians have become more selective with adjuvant immunotherapy in endometrial cancer. The study showed minimal benefit for pMMR patients and less impressive gains overall in its lower-risk population compared to advanced disease trials. This has led to a practice of reserving adjuvant chemo-IO primarily for stage 3 dMMR patients.

Based on translational data from the RUBY trial, experts are most cautious about recommending frontline checkpoint inhibitors for patients in the "No Specific Molecular Profile" (NSMP) subgroup of pMMR endometrial cancer, suggesting this group may not benefit.

Potent responses to chemo-immunotherapy are promoting a shift toward neoadjuvant treatment for advanced endometrial cancer. Waiting six cycles often achieves a response sufficient to allow for a minimally invasive hysterectomy instead of a more extensive primary debulking surgery.

While immunotherapy is transformational for DMMR endometrial cancer, its benefit is much smaller for the PMMR majority (two-thirds of patients). This reality requires more nuanced patient counseling and selective use in this population.

Even when neoadjuvant immunotherapy achieves an excellent systemic response in MSI-high endometrial cancer, residual disease frequently persists within the uterus. This finding cautions against forgoing hysterectomy based on imaging or systemic response alone.

The future of GYN oncology immunotherapy is diverging. For responsive cancers like endometrial, the focus is on refining biomarkers and overcoming resistance. For historically resistant cancers like ovarian, the strategy shifts to using combinatorial approaches (e.g., CAR-NKs, vaccines) to fundamentally alter the tumor microenvironment itself, making it more receptive to an immune response.

For endometrial or cervical cancer patients who progress after receiving a checkpoint inhibitor, re-challenging with a single-agent immunotherapy is a less desirable approach. Emerging data suggests that a combination therapy—such as an ICI paired with a TKI like lenvatinib or a bispecific antibody—offers a more promising chance of response.

Even in elderly or frail patients with MSI-high endometrial cancer, the rapid and effective tumor response from combination chemotherapy and immunotherapy often improves quality of life so significantly that it's the preferred approach over single-agent IO.

Early neoadjuvant trials show that while immunotherapy can eliminate metastatic endometrial cancer, residual disease often persists within the uterus. This suggests the uterus is a protected environment, tempering enthusiasm for omitting hysterectomy even in exceptional responders.