Primary completion results for a Phase 3 study evaluating atezolizumab (Tecentriq) in combination with usual therapy for HER2-positive metastatic breast cancer were posted on 2024-04-30. The terminated trial reported that 52.3 percentage of participants in the atezolizumab arm achieved progression-free survival, compared to 40.5 percentage of participants in the placebo arm.
Background
The study investigated atezolizumab (Tecentriq), in combination with paclitaxel, trastuzumab, and pertuzumab, for patients with metastatic HER2-positive breast carcinoma. Trastuzumab is a targeted therapy that works by attaching to HER2 receptors on cancer cells. The trial aimed to assess the efficacy and safety of adding atezolizumab to this established regimen in patients with metastatic or recurrent breast adenocarcinoma, including those with Stage III breast cancer.
Trial design
The terminated Phase 3 study (NCT03199885) enrolled 190 participants with metastatic HER2-positive breast carcinoma, metastatic breast adenocarcinoma, recurrent HER2-positive breast carcinoma, recurrent breast adenocarcinoma, or Stage III breast cancer AJCC v7. The trial compared two arms: Arm I received pertuzumab, trastuzumab, taxane therapy (docetaxel or paclitaxel), and placebo; Arm II received pertuzumab, trastuzumab, taxane therapy, and atezolizumab. The trial's overall status is "TERMINATED".
Key results
The trial reported the following key measurements:
- 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
- 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
- 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
- Frequency of Adverse Events, Including Late Immune-related Toxicities:
- Arm I (Pertuzumab, Trastuzumab, Taxane Therapy, Placebo): 91 Participants
- Arm II (Pertuzumab, Trastuzumab, Taxane Therapy, Atezolizumab): 95 Participants
What this means
The results from this terminated Phase 3 study indicate that the addition of atezolizumab to standard therapy for HER2-positive metastatic breast cancer was associated with an improved progression-free survival rate. The atezolizumab arm showed a 52.3 percentage of participants with PFS, compared to 40.5 percentage of participants in the placebo arm. Overall survival was marginally higher in the atezolizumab arm at 87.4 percentage of participants versus 86.3 percentage of participants for placebo. However, the overall objective response rate was slightly lower in the atezolizumab arm at 77.9 percentage of participants compared to 79.4 percentage of participants in the placebo arm. Adverse events were reported in 95 participants in the atezolizumab arm, slightly more than the 91 participants in the placebo arm. The termination of the trial means that these results should be considered in that context, and further analysis may be needed to fully understand the implications for clinical practice.
Source
The information regarding these trial results was obtained from ClinicalTrials.gov, a public database of clinical studies. The results for the study NCT03199885, titled "Testing the Drug Atezolizumab or Placebo With Usual Therapy in First-Line HER2-Positive Metastatic Breast Cancer", were posted on 2024-04-30 on clinicaltrials.gov.