Trial results for Atezolizumab in first-line HER2-positive metastatic breast cancer were posted on ClinicalTrials.gov on 2025-12-30. The study found that 52.3% of participants receiving Atezolizumab with standard therapy achieved progression-free survival, compared to 40.5% in the placebo arm.
Background
This trial investigated the addition of Atezolizumab to standard therapy for patients with metastatic HER2-positive breast carcinoma. The standard therapy included paclitaxel, trastuzumab, and pertuzumab, which are commonly used in treating metastatic breast adenocarcinoma, recurrent breast adenocarcinoma, recurrent HER2-positive breast carcinoma, and Stage III breast cancer AJCC v7.
Trial design
This Phase III randomized trial (NCT03199885) enrolled 190 participants. The study aimed to evaluate the efficacy of Atezolizumab or placebo when added to usual therapy in patients with metastatic breast adenocarcinoma, metastatic HER2-positive breast carcinoma, recurrent breast adenocarcinoma, recurrent HER2-positive breast carcinoma, or Stage III breast cancer AJCC v7. Participants were randomized to either Arm I, receiving pertuzumab, trastuzumab, taxane therapy, and placebo, or Arm II, receiving pertuzumab, trastuzumab, taxane therapy, and Atezolizumab.
Key results
The trial measured several key outcomes:
- For Progression-Free Survival (PFS):
- Arm I (Pertuzumab, Trastuzumab, Taxane Therapy, Placebo): 40.5 percentage of participants
- Arm II (Pertuzumab, Trastuzumab, Taxane Therapy, Atezolizumab): 52.3 percentage of participants
- For Overall Survival (OS):
- Arm I (Pertuzumab, Trastuzumab, Taxane Therapy, Placebo): 86.3 percentage of participants
- Arm II (Pertuzumab, Trastuzumab, Taxane Therapy, Atezolizumab): 87.4 percentage of participants
- For Overall Objective Response:
- Arm I (Pertuzumab, Trastuzumab, Taxane Therapy, Placebo): 79.4 percentage of participants
- Arm II (Pertuzumab, Trastuzumab, Taxane Therapy, Atezolizumab): 77.9 percentage of participants
What this means
The results indicate an improvement in Progression-Free Survival with the addition of Atezolizumab to standard therapy, with 52.3% of participants in the Atezolizumab arm achieving this outcome compared to 40.5% in the placebo arm. While Overall Survival rates were similar between the two arms (87.4% for Atezolizumab vs. 86.3% for placebo), the objective response rate was slightly lower in the Atezolizumab arm (77.9% vs. 79.4%). The improvement in PFS suggests a potential benefit for Atezolizumab in delaying disease progression in this patient population, though the impact on overall survival and objective response requires further consideration.
Source
The information for these trial results was obtained from ClinicalTrials.gov, a public database of clinical studies. The results for study NCT03199885, titled "Testing the Drug Atezolizumab or Placebo With Usual Therapy in First-Line HER2-Positive Metastatic Breast Cancer," were posted on 2025-12-30 on clinicaltrials.gov.