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IMPORTANCEApproximately 25% of patients with early-stage breast cancer who receive (neo)adjuvant chemotherapy experience a recurrence within 5 years. Improvements in therapy are greatly needed.OBJECTIVE To determine if pembrolizumab plus neoadjuvant chemotherapy (NACT) in early-stage breast cancer is likely to be successful in a 300-patient, confirmatory randomized phase 3 neoadjuvant clinical trial. DESIGN, SETTING, AND PARTICIPANTSThe I-SPY2 study is an ongoing open-label, multicenter, adaptively randomized phase 2 platform trial for high-risk, stage II/III breast cancer, evaluating multiple investigational arms in parallel. Standard NACT serves as the common control arm; investigational agent(s) are added to this backbone. Patients with ERBB2 (formerly HER2)-negative breast cancer were eligible for randomization to pembrolizumab between November 2015 and November 2016.INTERVENTIONS Participants were randomized to receive taxane-and anthracycline-based NACT with or without pembrolizumab, followed by definitive surgery. MAIN OUTCOMES AND MEASURESThe primary end point was pathologic complete response (pCR). Secondary end points were residual cancer burden (RCB) and 3-year event-free and distant recurrence-free survival. Investigational arms graduated when demonstrating an 85% predictive probability of success in a hypothetical confirmatory phase 3 trial. RESULTSOf the 250 women included in the final analysis, 181 were randomized to the standard NACT control group (median [range] age, 47 [24.77] years). Sixty-nine women (median [range] age, 50 [27-71] years) were randomized to 4 cycles of pembrolizumab in combination with weekly paclitaxel followed by AC; 40 hormone receptor (HR)-positive and 29 triple-negative. Pembrolizumab graduated in all 3 biomarker signatures studied. Final estimated pCR rates, evaluated in March 2017, were 44% vs 17%, 30% vs 13%, and 60% vs 22% for pembrolizumab vs control in the ERBB2-negative, HR-positive/ERBB2-negative, and triple-negative cohorts, respectively. Pembrolizumab shifted the RCB distribution to a lower disease burden for each cohort evaluated. Adverse events included immune-related endocrinopathies, notably thyroid abnormalities (13.0%) and adrenal insufficiency (8.7%). Achieving a pCR appeared predictive of long-term outcome, where patients with pCR following pembrolizumab plus chemotherapy had high event-free survival rates (93% at 3 years with 2.8 years' median follow-up).CONCLUSIONS AND RELEVANCE When added to standard neoadjuvant chemotherapy, pembrolizumab more than doubled the estimated pCR rates for both HR-positive/ERBB2negative and triple-negative breast cancer, indicating that checkpoint blockade in women with early-stage, high-risk, ERBB2-negative breast cancer is highly likely to succeed in a phase 3 trial. Pembrolizumab was the first of 10 agents to graduate in the HR-positive/ERBB2-negative signature.

Background I-SPY 2 is a phase 2 standing multicenter platform trial designed to screen multiple experimental regimens in combination with standard neoadjuvant chemotherapy for breast cancer. The goal is to matching experimental regimens with responding patient subtypes. We report results for veliparib, a poly(ADP-ribose) polymerase (PARP) inhibitor, combined with carboplatin (VC). Methods Eligible women had ≥2.5 cm stage II/III breast cancer, categorized into 8 biomarker subtypes based on HER2, hormone-receptor status (HR) and MammaPrint. Patients are adaptively randomized within subtype to better performing regimens compared to standard therapy (control). Regimens are evaluated within 10 signatures, prospectively defined combinations of subtypes. VC plus standard therapy was considered for HER2-negative tumors and therefore evaluated in 3 signatures. The primary endpoint of I-SPY 2 is pathologic complete response (pCR). MR volume changes during treatment inform the likelihood that a patient will achieve pCR. Regimens graduate if and when they have a high (Bayesian) predictive probability of success in a subsequent phase 3 neoadjuvant trial within the graduating signature. Results VC graduated in triple-negative breast cancer with 88% predicted probability of phase 3 success. A total of 72 patients were randomized to VC and 44 to concurrent controls. Respective pCR estimates (95% probability intervals) were 51% (35%–69%) vs 26% (11%–40%). Greater toxicity of VC was manageable. Conclusion The design of I-SPY 2 has the potential to efficiently identify responding tumor subtypes for the various therapies being evaluated. VC added to standard therapy improves pCR rates specifically in triple-negative breast cancer.

Expression of KIT tyrosine kinase is critical for normal germ cell development and is observed in the majority of seminomas. Activating mutations in KIT are common in gastrointestinal stromal tumors and mastocytosis. In this study we examined the frequency and spectrum of KIT mutations in 54 testicular seminomas, 1 ovarian dysgerminoma and 37 non-seminomatous germ cell tumors (NSGCT). Fourteen seminomas (25.9%) contained exon 17 point mutations including D816V (6 cases), D816H (3 cases), Y823D (2 cases), and single examples of Y823C, N822K, and T801I. No KIT mutations were found in the ovarian dysgerminoma or the NSGCTs. In transient transfection assays, mutant isoforms D816V, D816H, Y823D, and N822K were constitutively phosphorylated in the absence of the natural ligand for KIT, stem cell factor (SCF). In contrast, activation of T801I and wild-type KIT required SCF. Mutants N822K and Y823D were inhibited by imatinib mesylate (Gleevec, previously STI571) whereas D816V and D816H were both resistant to imatinib mesylate. Biochemical evidence of KIT activation, as assessed by KIT phosphorylation and KIT association with phosphatidylinositol (PI) 3-kinase in tumor cell lysates, was largely confined to seminomas with a genomic KIT mutation. These findings suggest that activating KIT mutations may contribute to tumorigenesis in a subset of seminomas, but are not involved in NSGCT.

Background I-SPY2, a standing, multicenter, adaptive phase 2 neoadjuvant trial ongoing in high-risk clinical stage II/III breast cancer, is designed to evaluate multiple, novel experimental agents added to standard chemotherapy for their ability to improve the rate of pathologic complete response (pCR). Experimental therapies are compared against a common control arm. We report efficacy for the tyrosine kinase inhibitor neratinib. Methods Eligible women had ≥2.5 cm stage II/III breast cancer, categorized into 8 biomarker subtypes based on HER2, hormone-receptor status (HR), and MammaPrint. Neratinib was evaluated for 10 signatures (prospectively defined subtype combinations), with primary endpoint pCR. MR volume changes inform likelihood of pCR for each patient prior to surgery. Adaptive assignment to experimental arms within disease subtype was based on current Bayesian probabilities of superiority over control. Accrual to experimental arm stop at any time for futility or graduation within a particular signature based on Bayesian predictive probability of success in a confirmatory trial. The maximum sample size in any experimental arm is 120 patients, Results With 115 patients and 78 concurrently randomized controls, neratinib graduated in the HER2+/HR− signature, with mean pCR rate 56% (95% PI: 37 to 73%) vs 33% for controls (11 to 54%). Final predictive probability of success, updated when all pathology data were available, was 79%. Conclusion Adaptive, multi-armed trials can efficiently identify responding tumor subtypes. Neratinib added to standard therapy is highly likely to improve pCR rates in HER2+/HR2212; breast cancer. Confirmation in I-SPY 3, a phase 3 neoadjuvant registration trial, is planned.