Upfront Pembro Plus Chemo Boost Survival in Cervical Cancer

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CHICAGO — A new standard of care for patients with chemotherapy-naive persistent, recurrent, or metastatic cervical cancer is first-line therapy with the combination of the immune checkpoint inhibitor pembrolizumab (Keytruda) with platinum-based chemotherapy and paclitaxel ― with or without bevacizumab.

This is based on final overall survival results from the phase 3 randomized KEYNOTE-826 study, which showed that adding immunotherapy resulted in a 40% reduction in risk of death compared with chemotherapy alone for women with advanced cervical cancers expressing programmed cell death–ligand-1 (PD-L1).

“At this protocol-specified final analysis of KEYNOTE-826, the addition of immune therapy to chemotherapy with or without the antiangiogenic bevacizumab showed substantial and clinically meaningful improvement in survival,” said lead author Bradley J. Monk, MD, from HonorHealth Research Institute in Phoenix, Arizona.

He was speaking at a media briefing held prior to the American Society of Clinical Oncology (ASCO) 2023 in Chicago, where the results will be presented (abstract 5500).

“The results of this study solidify the addition of pembrolizumab to chemotherapy with or without bevacizumab in people with persistent, recurrent, or metastatic cervical cancer as the frontline standard of care for this disease. Survival significantly improved with this approach, regardless of PD-L1 expression, further supporting its use for all patients in this population,” commented ASCO Expert Merry Jennifer Markham, MD, from the University of Florida in Gainseville.

At the briefing, Monk raised the possibility that adding immunotherapy to the standard of care could offer a chance for cure for some patients with advanced or recurrent cervical cancer.

“Is it possible to cure a widely metastatic cancer, a solid tumor? And I think it probably is,” he said. “There’s a tail to this [survival] curve, and I can’t believe that in my lifetime we as a group, as a team, have sort of figured out ― and it’s not enough ― that we can actually cure some patients, and if not maybe cure, have them at least live a long time, so it’s exciting.”

Briefing co-moderater Julie R. Gralow, MD, chief medical officer and executive vice-president of ASCO, agreed that the survival benefit “is exciting to see, and in my long career as a breast medical oncologist, I’m pretty sure we cure some metastatic breast cancer. We definitely had patients who lived out their normal life span and died of something else after decades.

“But the definition of cure, sadly, in these situations is that you die of something else without evidence of disease, so we certainly need to do better here and be better able to use the word ‘cure’ in the metastatic setting,” she added.

Promising Start

As previously reported by Medscape Medical News, since 2014, the standard of care for treating patients with recurrent, persistent, or metastatic cervical cancer has been chemotherapy with a platinum compound, paclitaxel, and bevacizumab, based on the results of the GOG 240 study.

Immunotherapy with programmed cell death protein–1 (PD-1) inhibitors had previously shown efficacy as monotherapy in second- or later-line therapy for women with cervical cancer, but KEYNOTE 826 was the first study to show a benefit to promoting immunotherapy to the front ranks.

In the first interim analysis of the trial, reported at the 2021 annual meeting of the European Society for Medical Oncology (ESMO), after a median follow-up of 22 months, the combination of pembrolizumab and chemotherapy demonstrated significant improvement in progression-free survival (PFS) and overall survival (OS) compared with chemotherapy plus placebo in a biomarker-selected population, which consisted of patients with a combined positive score (CPS) for PD-L1 of 1 or greater.

Pembrolizumab had no apparent efficacy in patients whose tumors did not have detectable PD-L1, however.

Latest Results

Now the investigators are reporting the final analysis, conducted after a median follow-up of 39.1 months.The results are those for all comers (308 randomly assigned to receive pembrolizumab plus chemotherapy, and 309 assigned to receive chemotherapy plus placebo), as well as for the biomarker-selected population (consisting of all patients with PD-L1 CPS of 1 or greater) and for the subpopulation of patients with PD-L1 CPS of 10 or greater.

In the all-comers population, the median OS was 26.4 months for patients who received pembrolizumab, compared with 16.8 months for those who received placebo. The 24-month OS rates were 52.1% and 38.7%, respectively. The difference translated into a hazard ratio (HR) for death with pembrolizumab of 0.63 (P < .0001).

In the biomarker-selected population (273 assigned to pembrolizumab and 275 assigned to placebo), the respective median OS was 28.6 months vs 16.6 months, with 24-month OS rates of 53.5% vs 39.4%, which translates into an HR for death with pembrolizumab of 0.60 (P < .0001).

Not surprisingly, the best responses to the addition of the PD-1 inhibitor were seen among patients with a PD-L1 CPS of 10 or greater (158 assigned to pembrolizumab and 159 assigned to placebo). In this subgroup, the median OS was 29.6 months with the immune checkpoint inhibitor added to chemotherapy, vs 17.4 months for chemotherapy plus placebo. The respective 24-month OS rates were 54.4% and 42.5%, and the HR for overall survival favoring pembrolizumab was 0.58 (P < .0001).

Median PFS 12-month PFS rates also favored pembrolizumab in both the total patient population and the biomarker-selected groups, with median PFS of approximately 10.4 months with pembrolizumab vs approximately 8.2 months with placebo.

The safety profile was manageable, with adverse events as expected from the safety profiles of the individual drugs in the combined regimen. No new safety signals have been seen since the interim analysis, Monk said.

Regimen Details

Patients were randomly assigned in a 1:1 ratio to receive pembrolizumab 200 mg or placebo every 3 weeks for up to 35 cycles plus platinum-based chemotherapy, with bevacizumab added at the investigator’s discretion. Approximately two thirds of patients in each study arm received bevacizumab.

The dual primary endpoints of PFS and OS were each tested sequentially in patients with a PD-L1 CPS of 1 or greater in both the intention-to-treat or “all-comers” population and in patients with a PD-L1 CPS of 10 or greater.

Patient characteristics were generally well balanced between the treatment groups, except that a slightly higher proportion of patients in the pembrolizumab had tumors of squamous cell histology compared with the placebo group (76.3% vs 68.3%).

KEYNOTE-826 was funded by Merck & Co. Monk has received honoraria and has participated in consulting/advising and speaker’s bureau activity with Merck and other companies. Gralow has had a consulting or advisory role with Genentech and Roche. Markham has had a consulting/advisory role for GSK and has received institutional research funding from Merck and other companies.

American Society of Clinical Oncology (ASCO) 2023: Abstract 5500.

Neil Osterweil, an award-winning medical journalist, is a long-standing and frequent contributor to Medscape.

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