Giving dual checkpoint blockade ahead of chemoradiation yields a high 3-year survival rate for patients with locally advanced cervical cancer, particularly for those with “hot” tumors, according to updated data from the phase 2 COLIBRI-1 trial.

Among 40 patients with locally advanced cervical cancer who were treated with one cycle of nivolumab/ipilimumab before standard chemoradiation, overall survival was 90% at 3 years. Outcomes were especially good for patients with immunologically hot tumors, all of whom were alive at 3 years, with no progression-free survival events.

The findings, reported at ESMO Gynecological (ESMO Gyn) Cancers Congress 2026 in Copenhagen, Denmark, add to evidence that immunotherapy has a role in treating locally advanced cervical cancer, and they underscore the importance of the tumor microenvironment, experts said.

But with its small size, the trial should be viewed as exploratory, said presenter Florence Joly, MD, PhD, a medical oncologist at the Centre François Baclesse in Caen, France.

“This is just the beginning,” Joly said, adding that her team will soon report further biological analyses that may shed more light on which patients benefit from induction immunotherapy.

Priming the Immune Response

Immune checkpoint blockade is part of standard care for patients with advanced or metastatic cervical cancer. And in the phase 3 KEYNOTE-A18 trial, pembrolizumab + concurrent chemoradiation improved survival outcomes compared with chemoradiation alone among patients with high-risk locally advanced disease.

However, Joly said, key questions remain about how best to sequence and intensify immunotherapy and which patients should receive it.

The multicenter COLIBRI-1 trial tested the strategy of giving dual checkpoint blockade just before chemoradiation. The aim, Joly said, is to prime the tumor immune microenvironment, which may improve response to standard therapy.

The trial enrolled 40 patients with stage IB3 to IVA locally advanced cervical cancer; roughly two thirds had stage III or IV disease. All patients received one cycle of immunotherapy (nivolumab 3 mg/kg on days 1 and 15 + ipilimumab 1 mg/kg on day 1), followed by chemoradiation. Maintenance nivolumab was given at 480 mg monthly for 6 months (with 85% of patients completing the full course).

Serial tumor biopsies were collected at baseline, after induction immunotherapy, and after chemoradiation to characterize the tumor immune microenvironment, including infiltration by CD8+ and CD4+ T cells. Tumors were also classified as immunologically hot or cold based on a 27-gene signature.

After a median follow-up of 40 months, there were five deaths (12.5%) and eight progression-free survival events. The 3-year overall survival rate was 90%, whereas 3-year progression-free survival was 83%.

There were no deaths among patients with earlier-stage disease, Joly said, while overall survival was 85% among those with stage III or IV disease, with a progression-free survival rate of 77%.

Study discussant Alina Sturdza, MD, of the Medical University of Vienna in Vienna, Austria, called the outcomes “fantastic.”

Sturdza contextualized the results against other recent trials of patients with locally advanced cervical cancer, noting that overall survival at 3 years now exceeds 80%. It’s a threshold, she said, that would have been unthinkable just a decade ago when 3-year overall survival was around 50%-60%.

Hot and Cold

Joly also reported exploratory subgroup analyses, where differences emerged based on tumor immune signatures. Of patients with hot tumors at baseline, all were alive and progression-free at 3 years; among those with cold tumors, overall survival was 86%, while progression-free survival was 76%.

However, over one third of patients with initially cold tumors converted to a hot immune signature after induction immunotherapy. And their outcomes were comparable to those of patients whose tumors started out hot, Joly said.

Among those converters, 3-year overall survival was 100%, while progression-free survival was 95%. That compared with rates of 73% and 60%, respectively, for patients with persistently cold tumors.

“The immune microenvironment is very important,” Sturdza said. “The cold tumors are doing poorly, but with the induction immunotherapy, some of them get hot and have a better prognosis.”

At the same time, both she and Joly stressed that the data are from a limited number of patients and should be considered hypothesis generating.

In terms of safety, Joly noted that the updated data showed no new signals. Rates of grade 3 or higher treatment-related adverse events were 2.5% during induction immunotherapy, 30% during chemoradiation, and 20% during the maintenance phase. There were no deaths due to adverse events.

Questions Going Forward

In an interview, Sturdza said COLIBRI is a “meaningful trial but exploratory” and that several questions remain.

She noted that the trial enrolled a highly selected patient population — with nearly all having squamous cell carcinoma, a histology that generally responds better to treatment than adenocarcinoma.

In addition, Sturdza said, 10% of patients underwent optional surgery before adjuvant nivolumab, while another 10% did not receive brachytherapy, which she considers essential in the radical treatment of locally advanced cervical cancer. Data on radiation doses were lacking, as well.

“There are too many variables,” Sturdza told Medscape Medical News. “Although the overall survival is impressive, the number of patients is too small to change clinical practice.”

Still, she believes the trial points toward a future of increasingly individualized treatment — with immune profiling potentially guiding which patients receive which treatment sequence.

“If the results of COLIBRI-1 are reproducible in a larger cohort,” Sturdza said, “definitely a broader use of induction immunotherapy ahead of chemoradiation may be in place.”

The COLIBRI-2 trial is underway, comparing induction nivolumab + relatlimab with nivolumab alone, followed by chemoradiation and nivolumab maintenance.

The trial was funded by Bristol Myers Squibb. Joly reported having financial relationships with GSK, AstraZeneca, Roche, and others. Sturdza reported having financial relationships with Elekta AB; Varian Medical Systems, Inc.; GSK; and others.