Nivolumab (Opdivo) produced a clinical complete response (CR) rate of 68.2% and a pathological best response rate of 100% in patients with stage I to III surgically resectable mismatch repair–deficient (dMMR) endometrial cancer, according to results from the phase 2 NIVEC trial (NCT05795244) presented during the 2026 ESMO Gynaecological Cancers Congress.1
Among 22 evaluable patients who completed treatment, 15 achieved a clinical CR, with no evidence of tumor on imaging and biopsy. Eight of those 15 chose to forgo surgery, instead undergoing nonoperative surveillance every 3 months. No disease recurrence was observed in any patient during the follow-up period.
“A CR was achieved in 15 patients with surgically resectable dMMR endometrial cancer following nivolumab treatment,” Yong Jae Lee, MD, PhD, a professor in the Department of Obstetrics and Gynecology at Yonsei University College of Medicine in Seoul, South Korea, said during the presentation. “PD-1 blockade may represent a potential fertility preservation treatment option for patients with dMMR endometrial cancer.”
Top Takeaways From the Phase 2 NIVEC Trial
- Nivolumab induced deep responses in surgically resectable dMMR endometrial cancer, achieving a clinical CR rate of 68.2% in the phase 2 NIVEC trial.
- Eight of the 15 patients who achieved a clinical CR opted to forgo surgery and undergo surveillance every 3 months, with no disease recurrences observed during follow-up.
- Nivolumab demonstrated a manageable safety profile, with grade 3 adverse effects occurring in 3 patients and no permanent treatment discontinuations reported.
How was NIVEC designed?
NIVEC was a multicenter, prospective phase 2 study enrolling patients with stage I to III surgically resectable dMMR or microsatellite instability–high endometrial cancer, including carcinosarcoma.1,2 Patients were required to have an ECOG performance status of 0 or 1 and have received no prior immune checkpoint inhibitor therapy.
Eligible patients received intravenous nivolumab at 480 mg every 4 weeks for 6 cycles.1 Following treatment, patients underwent imaging and endometrial biopsy: those with residual disease proceeded to surgery followed by adjuvant therapy, while those achieving a clinical CR were offered nonoperative follow-up every 3 months.
The primary end point was pathologic or clinical CR rate. Secondary end points included overall response rate, progression-free survival, overall survival, and safety.
At baseline, the median patient age was 51 years (range, 27-75). Clinical stage distribution consisted of stage IA (54.5%), IB (13.6%), IIIB (4.5%), and IIIC (31.8%). Endometrioid histology was present in 95.5% of patients, 95.5% had wild-type p53 status, and approximately half (54.5%) had well-differentiated tumors.
What did the safety analysis show?
Grade 3 adverse effects (AEs) were observed in 3 patients, and no AEs led to permanent discontinuation of nivolumab. The most common any-grade AEs were skin rash/dermatitis (22.7%), hypothyroidism/thyroiditis (13.6%), and increased aspartate aminotransferase/alanine aminotransferase levels (11.4%). Grade 3 pneumonitis improved after hospitalization and steroid treatment. Instances of grade 3 skin rash were well controlled with topical and oral steroids.
Disclosures: Lee reported personal financial interests with AstraZeneca, MSD, GSK, and Takeda. He also reported institutional financial interest with Corcept Therapeutics and ONO.
References
- Lee YJ, Lim MC, Cho HW, et al. A phase II study of induction PD-1 blockade (nivolumab) in patients with surgically completely resectable mismatch repair deficient endometrial cancer (NIVEC). Presented at: 2026 ESMO Gynaecological Cancers Congress; June 17-19, 2026; Copenhagen, Denmark. Abstract 70O.
- Study of induction PD-1 blockade (nivolumab) in patients with surgically complete resectable mismatch repair deficient endometrial cancer (NIVEC). ClinicalTrials.gov. Updated May 13, 2025. Accessed June 19, 2026. https://clinicaltrials.gov/study/NCT05795244
