Phase III double-blind randomized placebo controlled trial of atezolizumab in combination with carboplatin and paclitaxel in women with advanced/recurrent endometrial carcinoma: the Asian cohort of the AtTEnd/ENGOT-EN7 trial.

Objective: This post-hoc analysis of the AtTEnd trial explored differences in the prognostic characteristics and in the efficacy of atezolizumab between Asians and non-Asians.

Methods: The role of Asian race was evaluated on progression-free survival (PFS) using Cox-models and on time to appearance of new lesions using Fine and Gray models.

Results: From October 2018 to February 2022, 549 patients were randomized, of whom, 20.4% were Asian. Asians showed a better prognostic profile in terms of age, body mass index, Eastern Cooperative Oncology Group performance status, disease status and previous treatments. The prognostic impact of Asian race on PFS was confirmed in the placebo arm (adjusted hazard ratio [HR]=0.41; 95% confidence interval [CI]=0.24-0.70). In proficient mismatch repair (pMMR) tumors, the HRs for PFS comparing atezolizumab versus placebo were 0.82 (95% CI=0.63-1.05) in non-Asians, and 1.42 (95% CI=0.80-2.50) in Asians. In the pMMR population randomized to atezolizumab, the subdistribution HRs comparing Asians to non-Asians were 0.68 (95% CI=0.43-1.09) for progression with new lesions and 1.21 (95% CI=0.73-2.03) for progression without new lesions. Asians showed a higher occurrence of severe adverse events in atezolizumab compared to placebo arm (Asians: 82.1% vs. 64.3%, p=0.036; non-Asian: 63.3% vs. 63.6%, p=0.949).

Conclusion: Race seems to affect the safety of the addition of atezolizumab and, in pMMR tumors, also its efficacy. In the atezolizumab arm, Asian patients seem to have a lower cumulative incidence of new lesions when primary tumor regrowth was considered a competing risk, and a higher cumulative incidence of primary tumor regrowth when new lesions appearance was the competing risk.

Trial registration: ClinicalTrials.gov Identifier: NCT03603184.