MADRID – Research presented at the European Society for Medical Oncology (ESMO) Annual Meeting 2023 underline the benefit of adding immunotherapy to chemotherapy in advanced or recurrent endometrial cancer, and question whether adding the PARP inhibitor olaparib to the chemo-immunotherapy combination could provide further benefit.
In the AtTEnd trial, presented on Oct. 21, more than 550 patients with advanced newly diagnosed or recurrent disease were randomized to the antiprogrammed death–ligand 1 (PD-L1) antibody atezolizumab (Tecentriq) or placebo plus chemotherapy followed by maintenance atezolizumab or placebo.
– 28.1% vs. 17% at 2 years. The PFS benefit was much more pronounced among patients with mismatch repair-deficient (dMMR) disease – 50.4% vs. 16% at 2 years. Mismatch repair-deficient disease patients receiving atezolizumab also demonstrated an early overall survival benefit, according to findings from the interim analysis.
In the DUO-E trial, presented during the same Oct. 21 session, nearly 720 patients with newly diagnosed advanced or recurrent endometrial cancer were randomized to one of three groups: Chemotherapy alone with maintenance placebo, chemotherapy plus durvalumab (Imfinzi) with maintenance durvalumab, or chemotherapy plus durvalumab with maintenance durvalumab and the PARP inhibitor olaparib.
The results, published simultaneously in the Journal of Clinical Oncology, showed that adding durvalumab to chemotherapy followed by maintenance durvalumab with or without olaparib led to a significant improvement in PFS, compared with chemotherapy alone. As in the AtTEnd trial, this PFS was also more pronounced in dMMR patients.
Overall, Andrés Cervantes, MD, PhD, from the University of Valencia, Spain, and president of ESMO, explained that this research marks “very positive data for women with gynecological cancers,” with immunotherapy now incorporated into the standard of care.
However, an expert questioned whether the DUO-E trial clearly demonstrated the benefit of adding olaparib to immuno- and chemotherapy and whether certain subsets of patients may be more likely to benefit from the PARP inhibitor.
Inside AtTEnd
A growing body of research has shown that single agent immunotherapy is effective in treating endometrial cancer, particularly in tumors with dMMR, and that immunotherapy and chemotherapy may have a synergistic effect.
David S. P. Tan, MD, PhD, National University Cancer Institute, Singapore, who was not involved in the studies, commented that “the molecular classification of endometrial cancer is now leading us to areas that we didn’t think before [were] possible.”
The rationale for combining immunotherapy with chemotherapy, Dr. Tan explained, is that “the cytotoxicity you get from chemotherapy is partly dependent on immune activity within the tumor, and so it makes sense” to combine them.
This approach was borne out by recent positive PFS results from the NRG-GY018 trial of pembrolizumab plus chemotherapy in advanced endometrial cancer as well as from the RUBY trial of dostarlimab in primary advanced or recurrent disease.
To further investigate this chemo-immunotherapy strategy, the AtTEnd team enrolled patients with newly diagnosed or recurrent stage III-IV disease who had received no prior systemic chemotherapy for recurrence within the previous 6 months.
Overall, 551 patients from 89 sites across 10 countries were randomized to standard first-line chemotherapy – carboplatin plus paclitaxel – with either atezolizumab or placebo, followed by maintenance atezolizumab or placebo, which continued until confirmed disease progression.
The median age in the intention-to-treat population was 64-67 years. Nearly 23% of patients had dMMR tumors, and 67.2% had recurrent disease.
The baseline characteristics were well balanced and distributed between arms in the dMMR and all-comers population, said Nicoletta Colombo, MD, University of Milan–Bicocca, European Institute of Oncology Istituto di Ricovero e Cura a Carattere Scientifico, Italy, who presented the findings at ESMO.
Over a median follow up of 26.2 months, Dr. Colombo and colleagues observed a statistically significant improvement in PFS in the dMMR arm in favor of atezolizumab (hazard ratio, 0.36; P = .0005). At 2 years, 50.4% of patients receiving the immunotherapy were progression-free, compared with 16.0% in the placebo arm.
In all-comers, the PFS improvement with atezolizumab was less pronounced but remained significant (HR, 0.74; P = .0219).
A secondary analysis revealed, among dMMR patients, atezolizumab was associated with an overall survival advantage over placebo (HR, 0.41), with 75% of patients still alive at 2 years vs. 54.2% in the placebo arm. Dr. Colombo also noted a “clear trend” for improved overall survival with atezolizumab as well (HR, 0.82; P = .0483), but no PFS or overall survival benefit was seen with atezolizumab in MMR proficient (pMMR) patients.
Dr. Colombo said the safety profile of atezolizumab plus chemotherapy was “manageable,” with no differences in the rates of “major side effects,” although there was an increase in the rate of treatment-related grade ≥ 3 adverse events in the atezolizumab group (25.8% vs. 14.1%).
Dr. Tan noted that the AtTEnd trial revealed comparable results to earlier trials in this space but underlined that the survival curves in the interim analysis revealed a “red zone” of dMMR patients who do not respond to the combination and in whom immunotherapy is “not sufficient.”
Alongside this, Dr. Tan flagged a “blue zone” of dMMR patients who plateaued in both PFS and overall survival after 2 years. The question for these patients at this point is whether they need to continue immunotherapy beyond 24 months, he said.
But overall, Dr. Tan noted, the AtTEnd data “continue to validate practice-changing therapy for dMMR endometrial cancer patients” with immunotherapy plus chemotherapy, with the lack of benefit in pMMR disease underscoring an “unmet medical need.”