Trial results for atezolizumab in patients with Triple-negative Breast Cancer were posted on ClinicalTrials.gov on 2026-01-12. The study compared a regimen including an initial mono-atezolizumab window to a standard atezolizumab-chemotherapy approach, finding no significant difference in pathological complete response (pCR) rates. The Risk Difference for pCR between the two arms was -0.0327 (95% CI: -0.1307 to 0.0663).
Background
Triple-negative Breast Cancer (TNBC) is an aggressive form of breast cancer characterized by the absence of estrogen receptor, progesterone receptor, and HER2 expression. Treatment for TNBC often involves chemotherapy, and immune checkpoint inhibitors like atezolizumab, which targets PD-L1, have emerged as a therapeutic option, particularly in combination with chemotherapy, to enhance anti-tumor immune responses.
Trial design
This randomized, open-label, adaptive, multicenter Phase II trial (NCT04770272) was designed to compare two treatment strategies in patients with primary TNBC. The study enrolled 442 participants with tumor stages cT1c - cT4d (cN0 and cN+). Patients were stratified by PD-L1 expression on immune cells (IC-status) and anatomic tumor stage.
The trial included two arms:
- Arm A: A mono atezolizumab two-week window followed by atezolizumab - chemotherapy (carboplatin, paclitaxel, epirubicin).
- Arm B: Atezolizumab - chemotherapy (carboplatin, paclitaxel, epirubicin) without the initial window.
The trial aimed to identify biomarkers predicting early response or resistance to atezolizumab, both alone and in combination with chemotherapy, for future patient stratification.
Key results
The pathological complete response (ypT0/is, ypN0) rates were measured for both treatment arms:
- In Arm A (atezolizumab window + atezolizumab-CTX), 58 out of 112 participants achieved a pathological complete response.
- In Arm B (atezolizumab-CTX alone), 52 out of 117 participants achieved a pathological complete response.
A key analysis of the Risk Difference (RD) for pathological complete response between the two arms was calculated as -0.0327, with a 95% confidence interval ranging from -0.1307 to 0.0663.
Regarding adverse events, the total counts of reported events were:
- For Arm A: 3281, 1924, 847, and 376 adverse events were reported.
- For Arm B: 3313, 1937, 849, and 368 adverse events were reported.
What this means
The results indicate that incorporating a two-week mono-atezolizumab window prior to combination atezolizumab and chemotherapy did not lead to a statistically significant improvement in pathological complete response rates for patients with Triple-negative Breast Cancer. The Risk Difference analysis, with a 95% confidence interval that crosses zero, suggests no clear benefit for the window strategy over the standard combination therapy. The adverse event profiles were broadly comparable between the two treatment arms, further supporting the conclusion that the added window did not offer a distinct advantage in efficacy or safety.
Source
The information regarding these trial results was obtained from ClinicalTrials.gov, a public database of clinical studies. The results for study NCT04770272, titled "Study to Compare a Mono Atezolizumab Window Followed by a Atezolizumab - CTX Therapy With Atezolizumab - CTX Therapy," were posted on 2026-01-12 on clinicaltrials.gov.