Inside DUO-E
The burning question, however, was whether adding a PARP inhibitor to immunotherapy and chemotherapy would boost the survival outcomes further.
The DUO-E trial involved patients with newly diagnosed stage III/IV or recurrent endometrial cancer who had not received systematic therapy for advanced disease and were naive to both PARP inhibitors and immune-mediated therapy.
Overall, 718 patients were randomized to one of three arms: Chemotherapy alone followed by maintenance placebo, chemotherapy plus durvalumab with maintenance durvalumab, or chemotherapy plus durvalumab with maintenance durvalumab plus olaparib.
Maintenance was continued until disease progression or unacceptable toxicity, or the patients met another discontinuation criteria.
About half of patients were newly diagnosed, half had recurrent disease, and approximately one-fifth had dMMR disease, said Shannon Westin, MD, from the University of Texas MD Anderson Cancer Center, Houston, who presented the findings.
Compared with placebo plus chemotherapy, patients in both the durvalumab alone and durvalumab plus olaparib arms experienced a significant improvement in PFS (HR, 0.71; P = .003; and HR, 0.55; P < .0001, respectively).
This effect was amplified in dMMR patients with durvalumab (HR, 0.42) as well as with durvalumab plus olaparib (HR, 0.41).
In pMMR patients, PFS benefit was stronger in the durvalumab-olaparib arm vs. durvalumab (HR, 0.57 vs. 0.77).
Although the overall survival analysis remains exploratory, Dr. Westin noted a trend toward better overall survival in the two treatment arms vs. placebo (HR, 0.77 with durvalumab, and HR, 0.59 with durvalumab plus olaparib).
However, adding olaparib to the equation increased the rate of grade ≥ 3 adverse events – 67.2% vs. 54.9% with durvalumab and 56.4% with chemotherapy alone in the overall analysis. The addition of olaparib also led to treatment discontinuation in 24.4% of patients vs. 20.9% in the durvalumab arm and 18.6% in the chemotherapy alone arm.
Domenica Lorusso, MD, PhD, who was not involved in the study, commented that the marginal PFS benefit of adding olaparib in DUO-E is “not surprising” because the bar set by immunotherapy is “so high in this population that it’s very difficult” to go any higher.
But the results in pMMR patients reveal “a clear additional benefit” to olaparib, said Dr. Lorusso, from Fondazione IRCCS Istituto Nazionale dei Tumori, Milan.
“The main limitation of the trial,” she continued, “is that it was not powered to make a formal comparison between the two experimental arms.”
So, what then is the added benefit of olaparib? “Unfortunately, that remains an unanswered question,” Dr. Lorusso said.
AtTEnd was sponsored by the Mario Negri Institute for Pharmacological Research.
DUO-E was funded by AstraZeneca.
Dr. Colombo declares relationships with AstraZeneca, Clovis Oncology, Esai, GSK, Immunogen, Mersana, MSD/Merck, Nuvation Bio, OncXerna, Pieris, Roche, and Novocure.
Dr. Tan declares relationships with AstraZeneca, Karyopharm Therapeutics, Bayer, Roche, MSD, Genmab, Esai, PMV, BioNTech, Ellipses Pharma, Boehringer Ingelheim, Merck Serono, Takeda, and Clovis.
Dr. Westin declares relationships with AstraZeneca, Avenge Bio, Bayer, Bio-Path, Clovis, Genentech/Roche, GSK, Jazz Pharmaceuticals, Mereo, Novartis, Nuvectis, and Zentalis; and consulting and advisory roles for AstraZeneca, Caris, Clovis, Eisai, EQRx, Genentech/Roche, Gilead, GSK, Immunocore, ImmunoGen, Lilly, Merck, Mersana, Mereo, NGM Bio, Nuvectis, Seagen, Verastem, Vincerx, Zentalis, and ZielBio.
Dr. Lorusso declares relationships with PharmaMar, Merck Serono, Novartis, AstraZeneca, Clovis, Tesaro/GSK, Genmab, Immunogen, and Roche.
A version of this article first appeared on Medscape.com.