Clinical Trial of Neoadjuvant Chemotherapy With Atezolizumab or Placebo in Patients With Triple-Negative Breast Cancer Followed After Surgery by Atezolizumab or Placebo

NSABP B-59/GBG 96-GeparDouze is a prospective, randomized, double-blind, Phase III clinical trial. This is a collaborative study being conducted by NSABP Foundation, Inc. in partnership with the German Breast Group (GBG), and supported by funding by Genentech, a Member of the Roche Group, and F. Hoffmann-La Roche, Ltd. In this clinical trial of neoadjuvant and adjuvant administration of atezolizumab/placebo in patients with high risk triple-negative breast cancer, the potential incremental efficacy and safety of neoadjuvant administration of atezolizumab/placebo with a sequential regimen of weekly paclitaxel with every-3-week carboplatin followed immediately by neoadjuvant administration of atezolizumab/placebo with AC/EC will be evaluated. Patients will then undergo surgery. Following recovery from surgery, patients will initiate approximately 6 months of adjuvant therapy with atezolizumab/placebo and receive the same investigational agent they received pre-operatively. Administration of radiation therapy will be based on local standards at the discretion of patients and investigators, but if administered, atezolizumab/placebo will be administered concurrently. Adjuvant atezolizumab/placebo may be delayed until after completion of radiation therapy per investigator discretion. Patients with residual invasive cancer at the time of surgery may receive capecitabine concurrently with atezolizumab/placebo in the adjuvant setting per investigator discretion and local guidelines. Patients with germline BRCA1 or BRCA2 mutations with residual invasive cancer at the time of surgery may receive olaparib in the adjuvant setting per investigator discretion and local guidelines. Patients receiving olaparib must discontinue atezolizumab/placebo. The primary aims of the study are 1) to determine value of atezolizumab in improving pathologic complete response in the breast and post-therapy lymph nodes evaluated histologically (pCR breast and nodes \[(ypT0/Tis ypN0)\]), and 2) to determine the value of atezolizumab in improving event-free survival (EFS). Secondary aims include: pathologic complete response in the breast (ypT0/Tis); pathologic complete response in the breast and lymph nodes (ypT0 ypN0); positive nodal status conversion rate; overall survival; recurrence-free interval: distant disease-free survival; brain metastases free survival; and toxicity. The stratification factors for the study are: 1) clinical size of the primary tumor (1.1-3.0 cm; \> 3.0 cm); 2) nodal status as determined by protocol-specified criteria (negative, positive); 3) AC/EC (every 2 weeks; every 3 weeks); and 4) Region (North America; Europe). For patient eligibility, local testing on the diagnostic core must have determined the patient's tumor to be ER-negative, PgR-negative, and HER2-negative by current ASCO/CAP guidelines. Material from either the diagnostic core biopsy or the research biopsy must be sent for central testing for confirmation of ER, PgR, and HER2 to confirm eligibility. If local testing has determined a tumor to be HER2 equivocal or to have a borderline ER/PgR status (% IHC staining \< 10% for both), material may be submitted for central testing to determine eligibility. In order to proactively identify and further assess any cardiac toxicity that may occur with the combination of anthracyclines and atezolizumab, this study includes a cardiac safety lead-in for the first 60 patients who initiate AC/EC. The safety lead-in will consist of assessment of ECG and serum troponin-T obtained just prior to administration of the first dose of AC/EC, following completion of the administration of the 1st and 3rd cycle of AC/EC prior to initiation of the atezolizumab/placebo. An additional assessment of LVEF with echocardiogram or MUGA scan will also be obtained prior to the 3rd dose of AC/EC. In order to provide an early assessment of cardiac safety, results of the troponin-T assessments, ECGs, LVEF assessment, and cardiac safety data will be evaluated by the Data Safety Monitoring Board (DSMB) when the last of the initial 20 patients who initiate AC/EC undergo their scheduled post-surgery LVEF assessment. When the last of the first 60 patients to initiate AC/EC undergo their scheduled post-surgery LVEF assessment, results of the troponin assessments, ECGs, LVEF assessments, and cardiac safety data from all 60 patients will be evaluated by the DSMB. Research core biopsies of breast primary at baseline and 1-4 days prior to the second dose of atezolizumab/placebo are a study requirement for all patients. One to three representative blocks of residual primary tumor containing the maximum amount of tumor and node with the largest focus of metastasis is required from the definitive breast surgery if gross residual disease is greater than or equal to 1.0 cm. If gross residual disease is less than 1.0 cm, tissue should be submitted, if possible. Blood specimens will be collected on all patients at baseline for exploratory biomarker analysis and to support future correlative studies. Accrual to NSABP B-59/GBG 96-GeparDouze began in December 2017 and was completed in May 2021 with a total of 1550 patients randomized. Based on actual accrual and the decision to eliminate pCR as a co-primary endpoint, we recalculated the power to detect a hazard ratio of 0.70 attributed to the addition of atezolizumab, assuming a lost-to-follow-up rate of 0.00083 per month, using the actual accrual pattern for the power calculation. With 1550 patients accrued in 42 months, an additional 22 months follow up will allow us to obtain 252 events under the assumptions stated above, which will provide 80% power to detect a HR of 0.7 between the atezolizumab and the placebo arm at an overall 2-sided alpha level of 0.05.