AACR 2020: Adding Immunotherapy to Prostate Cancer Regimen in IMbassador250
Posted: Tuesday, May 5, 2020
Combination therapy using the anti–PD-L1 inhibitor atezolizumab plus the androgen receptor antagonist enzalutamide did not show any clinical benefit when compared with enzalutamide alone in patients with metastatic castration-resistant prostate cancer, according to the phase III IMbassador250 randomized clinical trial. Christopher J. Sweeney, MBBS, of the Dana-Farber Cancer Institute, Boston presented these results along with colleagues as part of the 2020 American Association for Cancer Research (AACR) Virtual Annual Meeting (Abstract CT014).
This study enrolled 759 men with castration-resistant metastatic prostate carcinoma who experienced disease progression with docetaxel or abiraterone. Patients had no prior exposure to immunotherapy or androgen-deprivation therapy. The men were randomly assigned 1:1 to receive either 1,200 mg of atezolizumab every 3 weeks plus 160 mg of enzalutamide daily or 160 mg of enzalutamide alone daily.
There was no apparent difference between the groups in terms of overall survival, as the group receiving atezolizumab had an overall survival of 15.2 months, compared with 16.6 months in the enzalutamide-alone group (hazard ratio = 1.12, P = .28). The 12-month overall survival rates were 64.7% and 60.6% for the combination and single-agent groups, respectively. The overall response rate was 14% with atezolizumab and 7% with enzalutamide alone. Subgroup analysis for prior docetaxel exposure, prior local therapy, measurable disease status, and PD-L1 expression showed no clinical benefit with atezolizumab over enzalutamide alone.
Nearly all patients experienced some adverse event while on the trial. Grade 3 or higher treatment-related adverse events occurred in 28.3% of patients in the combination group and 9.6% of patients in the single-agent group. Adverse events leading to discontinuation of therapy occurred in 14% of patients in the combination arm and 6% of patients in the single-agent arm. Seven patients treated with atezolizumab died, and one patient treated with enzalutamide alone died.
Disclosure: For a full list of author disclosures, visit abstractsonline.com.
