Destiny takes a hand
The protocol was changed following the approval in October 2021 of adjuvant abemaciclib in patients with high-risk ER+/HER2– disease.
“This was expected to result in a high rate of withdrawals due to safety concerns when combining a CDK4/6 inhibitor with an anti-PD-1, and this put the co-primary endpoint of EFS at risk,” Dr. Loi explained.
Therefore, the investigators amended the trial protocol to establish pCR as the sole primary endpoint and ceased accrual after 521 patients were randomized.
In addition, the primary efficacy population was modified to include 510 patients across 221 sites in 31 countries after Russian sites with a total of 11 patients closed due to Russia’s war on Ukraine.
And another hurdle, trial recruitment occurred from November 2019 through April 2022, during the COVID-19 pandemic.
Checkmate 7FL results
The pCR rate in the modified intention-to-treat (ITT) population was 24.5% for patients who received nivolumab, compared with 13.8% for patients who did not, translating in an odds ratio for benefit with the ICI of 2.05 (P = .0021),
In patients with PD-L1 expression in at least 1% of cells, a secondary endpoint, the respective pCR rates were 44.3% and 20.2%, with OR of 3.11, and a confidence interval indicating statistical significance.
Residual cancer burden (RCB) rates of 0 or 1 were also higher in the nivolumab-containing arm in both the modified ITT population (30.7% vs. 21.3%), and in the PD-L1–enriched population (54.5% vs. 26.2%).
In the safety population, which included 517 patients who received at least one dose of nivolumab or placebo, rates of overall adverse events and treatment-related adverse events were similar between the two arms, with the exception of two deaths from drug toxicity in Arm A (from pneumonitis in a patient 61 days after the last neoadjuvant cycles and hepatitis in a patient 51 days after) vs. no drug toxicity deaths reported in Arm B.
Safety of the nivolumab and neoadjuvant chemotherapy combinations was consistent with known safety profiles, with no new safety signals seen, Dr. Loi said.
KEYNOTE-756 details
The KEYNOTE-756 investigators had an easier time of it than Dr. Loi and colleagues. In fact, the trial “is the first fully accrued phase 3 immunotherapy study in high-risk, early-stage ER-positive, HER2-negative breast cancer, and it met one of its primary endpoints, pCR,” Dr. Cardoso said.
She noted that in the adaptive I-SPY2 trial, the addition of pembrolizumab to neoadjuvant chemotherapy resulted in a nearly threefold improvement in estimated pCR rates in patients with ER+/HER2– tumors, indicating that the role of immunotherapy in this population warranted further exploration.
In the placebo-controlled KEYNOTE-756 trial, treatment-naive patients with locally confirmed invasive ductal breast carcinoma with stage T1c or T2 tumors 2 cm or larger with nodal status CN1 or 2, or T3 and T4 tumors with nodal status CN0-2 were enrolled.
In most centers (Eastern Europe and China being the exceptions) patients were stratified by PD-L1 status, nodal status, anthracycline regimen chosen (AC or epirubicin-cyclophosphamide [EC]) and by degree of ER-positivity. Patients, 1,278 in total, were then randomly assigned to pembrolizumab for four cycles plus paclitaxel for 12 weeks, followed by AC or EC for four cycles plus pembrolizumab, or to the same regimen without pembrolizumab.
Following surgery, patients went on to endocrine therapy for up to 10 years, with or without 6 months of additional pembrolizumab every 6 months.