New Immunotherapy Approaches in Early-Stage Breast Cancer: The Neo-CheckRay Trial Findings

The Neo-CheckRay phase 2 clinical trial, conducted across sites in Belgium and France, investigated whether adding immunotherapy to standard neoadjuvant chemotherapy and radiation could improve surgical outcomes for patients with early-stage, high-risk, hormone receptor-positive (ER+), HER2-negative breast cancer. According to the study published in Nature Medicine, researchers evaluated the efficacy of durvalumab and oleclumab combined with immune-priming stereotactic body radiation therapy (iSBRT) before surgery. While the study provided significant insights into the biological response of tumors to these combinations, it highlights the ongoing challenge of achieving pathological complete response (pCR) in this specific breast cancer subtype.

How the Neo-CheckRay Trial Was Designed

The trial utilized a prospective, randomized, multicenter, open-label design to test three distinct treatment arms in 147 randomized patients. As detailed in the ClinicalTrials.gov registry (NCT03875573), participants received neoadjuvant chemotherapy consisting of paclitaxel followed by dose-dense doxorubicin and cyclophosphamide. The treatment arms were divided into three groups: chemotherapy plus iSBRT alone, chemotherapy plus iSBRT and durvalumab, and chemotherapy plus iSBRT, durvalumab, and oleclumab. The primary objective was to measure the Residual Cancer Burden (RCB) at the time of surgery, aiming for an RCB 0 or 1 score, which indicates little to no remaining tumor presence.

Understanding the Role of Immunotherapy in ER+ Breast Cancer

Historically, hormone receptor-positive (ER+), HER2-negative breast cancer has shown limited response to immunotherapy compared to triple-negative breast cancer. The Neo-CheckRay trial attempted to overcome this resistance by using iSBRT as an “immune primer” to make the tumor environment more visible to the immune system. Durvalumab, a PD-L1 inhibitor, and oleclumab, an anti-CD73 antibody, were introduced to block pathways that tumors often use to evade immune destruction. According to the study, researchers performed baseline and on-treatment biopsies to analyze biomarkers, including PD-L1 expression and gene-signature changes, to better understand how these treatments modulate the tumor microenvironment.

Safety and Clinical Implications

Monitoring for immune-related adverse events was a priority throughout the trial. Because this was an open-label study, investigators maintained close surveillance of patients receiving durvalumab and oleclumab. An independent data monitoring committee (IDMC) oversaw the study’s progress, conducting three safety analyses and one futility analysis to ensure participant well-being. As of the final database lock on December 4, 2025, the trial results contribute to the broader medical understanding of how radiation and immunotherapy might be sequenced to treat early-stage, high-risk disease. These findings are essential for clinicians weighing the risks of intensified systemic therapy against the potential benefits of improved surgical outcomes.

Key Takeaways for Patients and Providers

• Target Population: The trial focused specifically on patients with high-risk, ER+/HER2-negative breast cancer who typically have lower response rates to traditional immunotherapy.
• Study Design: The trial used a 1:1:1 randomization across three arms, incorporating iSBRT as a unique component to prime the immune system before surgery.
• Clinical Goal: The primary endpoint was an RCB score of 0 or 1 at surgery, a metric that correlates with better long-term survival in breast cancer patients.
• Expert Oversight: The study was an investigator-initiated academic trial sponsored by the Institut Jules Bordet, ensuring independent analysis of the immunotherapy combinations.

Frequently Asked Questions

What is an RCB score?
The Residual Cancer Burden (RCB) score is a standardized method used by pathologists to quantify the extent of residual disease in the breast and lymph nodes after neoadjuvant chemotherapy. An RCB of 0 is equivalent to a pathological complete response (pCR).

Why was iSBRT used in this trial?
Stereotactic body radiation therapy (SBRT) was delivered to the primary tumor in three fractions. The researchers hypothesized that this “immune-priming” would trigger an inflammatory response, potentially enhancing the efficacy of the immunotherapy drugs durvalumab and oleclumab.

What happens next for these patients?
The trial participants continue to be monitored. Future analyses are planned for 3 and 5 years post-surgery to evaluate Event-Free Survival (EFS) and other long-term efficacy outcomes, which will provide a more comprehensive picture of the treatment’s impact on patient longevity.