In the I-SPY2.2 trial, the combination of datopotamab deruxtecan (Dato-DXd) and durvalumab demonstrated a high pathologic complete response rate in specific subtypes of high-risk, stage II/III breast cancer. The study, presented at the European Society for Medical Oncology (ESMO) Congress 2024, suggests this regimen could potentially replace standard chemotherapy in certain patient populations.
The trial incorporated novel therapies into the neoadjuvant treatment of high-risk breast cancer using a sequential design. Meghna S. Trivedi, MD, MS, Herbert Irving Assistant Professor of Medicine at Columbia University Irving Medical Center, presented the findings, highlighting the potential of Dato-DXd plus durvalumab, particularly in immune-positive and "all-negative" subtypes.
Rationale for Combination Therapy
Preclinical data indicates that topoisomerase I inhibitors like Dato-DXd can enhance antitumor immune response, improving the efficacy of anti-PD-L1 therapy. The phase Ib/II BEGONIA trial previously showed a 79% response rate and median progression-free survival of nearly 14 months with this combination in first-line metastatic triple-negative breast cancer.
I-SPY2.2 Trial Design
The I-SPY2.2 trial is a phase II neoadjuvant sequential, multiple-assignment randomization trial for high-risk stage II/III breast cancer. It involves three treatment blocks: initial randomization to experimental agents (block A), followed by a taxane-based regimen (block B), and then anthracycline/cyclophosphamide (block C) if needed. Treatment assignment is based on biomarkers defining hormone receptor status, HER2 status, predicted benefit from immunotherapy, DNA damage repair deficiency (DRD), and luminal signaling.
Response to therapy was evaluated using breast MRI and core biopsies to assess predicted residual cancer burden (pre-RCB), guiding decisions on treatment de-escalation or early escalation.
Outcomes of Dato-DXd Plus Durvalumab Cohort
106 patients initiated treatment with Dato-DXd plus durvalumab in block A. The overall observed pathologic complete response rate was 50%. Dr. Trivedi noted that the regimen was most effective in the immune-positive subtype, where it "graduated" after block A, exceeding the prespecified threshold for success.
In the immune-positive subtype, while the full treatment strategy (blocks A + B + C) resulted in a 79% pathologic complete response rate, the dynamic control group also showed a high rate (78%). However, a significant finding was that in patients who achieved a pathologic complete response, 54% did so after block A, and 92% after block B, potentially avoiding anthracycline/cyclophosphamide.
In the hormone receptor-negative/immune-negative/DRD-negative (all-negative) subtype, the full treatment strategy also graduated, with a 44% pathologic complete response rate in the intent-to-treat population (56% in the pre-RCB–met population), significantly exceeding the 16% rate in the dynamic control.
Expert Commentary
Fatima Cardoso, MD, Director of the Breast Unit at the Champalimaud Clinical Center in Lisbon, highlighted the effectiveness of the regimen in the hard-to-treat hormone receptor-negative, HER2-negative, immune-negative, and DNA damage repair–deficient subtype. However, she cautioned about the toxicity associated with the full three-block regimen, including a toxic death, and emphasized the need for phase III trials to evaluate long-term benefits.
Dr. Cardoso also raised questions about identifying tumors that achieve pathologic complete response after block A alone and optimizing trial designs for drugs that graduate from I-SPY2.2.
