Haley, Barbara

PURPOSE Neoadjuvant immunotherapy (IO) has become the standard of care for early-stage triple-negative breast cancer (TNBC), but not yet for other subtypes. We previously developed a clinical-grade mRNA-based immune classifier (ImPrint) predicting response to IO that is now being used in I-SPY2.2 as part of the response predictive subtypes. We report the performance of ImPrint in hormone receptor–positive and human epidermal growth factor receptor 2–negative (HR+HER2–) patients from five IO arms. METHODS A total of 204 HR+HER2– (MammaPrint high-risk) patients from five IO arms (anti–PD-1, anti–PD-L1/poly [ADP-ribose] polymerase inhibitor combination, anti–PD-1/toll-like receptor 9 dual-IO combination, and anti–PD-1 ± lymphocyte activation gene 3 dual-IO combination) and 191 patients from the chemotherapy-only control arm were included in this analysis. Patients were classified as ImPrint+ (likely sensitive) versus ImPrint– (likely resistant), using pretreatment mRNA. Performance of ImPrint for predicting pathologic complete response (pCR) to IO-containing arms was characterized and compared with tumor grade (III), MammaPrint (ultra) High2 risk (MP2), and estrogen receptor (ER)-low (ER ≤ 10%). RESULTS Overall, the pCR rate across the five IO arms was 33%. 26% of HR+HER2– patients were ImPrint+, and pCR rates with IO were 75% in ImPrint+ versus 17% in ImPrint–, with the highest pCR rate >90% in a dual-IO arm. In the control arm, pCR rates were 33% in ImPrint+ and 8% in ImPrint–. Tumor grade (III), MP2, and ER-low showed pCR rates in IO of 45%, 56%, and 63%, respectively, with lower pCR odds ratios (OR < 7.5) compared with ImPrint (OR = 14.5). CONCLUSION Using an accurate selection strategy, HR+HER2– patients could achieve pCR rates similar to what is seen with best neoadjuvant therapies in TNBC and HER2+ (ie, pCR rate >65%-70%). ImPrint, an Food and Drug Administration IDE-enabled assay, may represent a way to identify HR+HER2– patients for IO that best balances likely benefit versus risk of serious immune-related adverse events.

ImportanceThere has been little consideration of genomic risk of recurrence by breast cancer subtype despite evidence of racial disparities in breast cancer outcomes.ObjectiveTo evaluate associations between clinical trial end points, namely pathologic complete response (pCR) and distant recurrence–free survival (DRFS), and race and examine whether gene expression signatures are associated with outcomes by race.Design, Setting, and ParticipantsThis retrospective cohort study used data from the Investigation of Serial Studies to Predict Your Therapeutic Response With Imaging and Molecular Analysis 2 (I-SPY 2) multicenter clinical trial of neoadjuvant chemotherapy with novel agents and combinations for patients with previously untreated stage II/III breast cancer. Analyses were conducted of associations between race and short- and long-term outcomes, overall and by receptor subtypes, and their association with 28 expression biomarkers. The trial enrolled 990 female patients between March 30, 2010, and November 5, 2016, with a primary tumor size of 2.5 cm or greater and clinical or molecular high risk based on MammaPrint or hormone receptor (HR)-negative/ERBB2 (formerly HER2 or HER2/neu)–positive subtyping across 9 arms. This data analysis was performed between June 10, 2021, and October 20, 2022.ExposureRace, tumor receptor subtypes, and genomic biomarker expression of early breast cancer.Main Outcomes and MeasuresThe primary outcomes were pCR and DRFS assessed by race, overall, and by tumor subtype using logistic regression and Cox proportional hazards regression models. The interaction between 28 expression biomarkers and race, considering pCR and DRFS overall and within subtypes, was also evaluated.ResultsThe analytic sample included 974 participants (excluding 16 self-reporting as American Indian or Alaska Native, Native Hawaiian or Other Pacific Islander, or multiple races due to small sample sizes), including 68 Asian (7%), 120 Black (12%), and 786 White (81%) patients. Median (range) age at diagnosis was 47 (25-71) years for Asian, 49 (25-77) for Black, and 49 (23-73) years for White patients. The pCR rates were 32% (n = 22) for Asian, 30% for Black (n = 36), and 32% for White (n = 255) patients (P = .87). Black patients with HR-positive/ERBB2-negative tumors not achieving pCR had significantly worse DRFS than their White counterparts (hazard ratio, 2.28; 95% CI, 1.24-4.21; P = .01), with 5-year DRFS rates of 55% (n = 32) and 77% (n = 247), respectively. Black patients with HR-positive/ERBB2-negative tumors, compared with White patients, had higher expression of an interferon signature (mean [SD], 0.39 [0.87] and −0.10 [0.99]; P = .007) and, compared with Asian patients, had a higher mitotic score (mean [SD], 0.07 [1.08] and −0.69 [1.06]; P = .01) and lower estrogen receptor/progesterone receptor signature (mean [SD], 0.31 [0.90] and 1.08 [0.95]; P = .008). A transforming growth factor β signature had a significant association with race relative to pCR and DRFS, with a higher signature associated with lower pCR and worse DRFS outcomes among Black patients only.Conclusions and RelevanceThe findings show that women with early high-risk breast cancer who achieve pCR have similarly good outcomes regardless of race, but Black women with HR-positive/ERBB2-negative tumors without pCR may have worse DRFS than White women, highlighting the need to develop and test novel biomarker-informed therapies in diverse populations.

Abstract Background Transcriptomic immune-related gene signatures have been associated with achievement of pathologic complete response (pCR) and prognosis in the neoadjuvant setting. I-SPY 2 is a multicenter, phase 2 platform trial using response-adaptive randomization within subtypes defined by receptor status (HR/HER2) and MammaPrint (MP) risk to evaluate novel agents as neoadjuvant therapy for women with high-risk breast cancer. Given racial disparities in mortality from breast cancer and the paucity of racial demographic data from clinical trials, we aimed to evaluate the association between racial groups and baseline characteristics, including expression-based subtypes and immune signatures, treatment response, and prognosis of patients enrolled in the I-SPY 2 TRIAL. Methods Our study population included 990 I-SPY 2 patients. 15 patients identified as part of a racial group with &lt;10 patients enrolled in the trial and were excluded from analysis. Pre-treatment expression data was available for 971 patients. Follow-up data was available for 907 patients; median follow-up time of 4.4 yrs. Chi-square test was used to assess associations between racial groups and pre-treatment SBR grade, HR/HER2 defined subtypes, intrinsic subtype (defined by BluePrint 80-gene molecular subtyping) and residual cancer burden (RCB) class. Logistic regression was used to evaluate race association with pCR. Cox proportional hazard modeling was used to assess the association between racial groups and event free survival (EFS) in a univariate setting, adjusting for pCR status. Association between racial groups and 28 expression signatures related to immune, proliferation, ER and HER2 pathway was analyzed using ANOVA with post-hoc Tukey test in the overall population and in each receptor subtype. Results Of 975 patients included in our analysis, 787 (81%) were White, 68 (7%) were Asian, and 120 (12%) were Black or African American. No significant associations between race and pre-treatment SBR grade (p=0.49), HR/HER2 defined subtypes (p=0.09), or expression-based subtypes (p=0.25) were observed. pCR rates do not significantly differ by racial groups (Odds ratio of pCR relative to White: 1.00 for Asian and 0.89 for Black or African American); and no significant differences in RCB class distribution by race was observed (p=0.88). Event free survival was not associated with patient racial group in a univariate Cox model (Hazard ratio relative to White: 1.10, p=0.73 for Asian and 1.37, p=0.13 for Black or African American). Among the 28 expression signatures evaluated, four were differentially expressed among racial groups within the overall population (F-test p&lt;0.05): IFN module, B cell signature, Dendritic cell signature, and Mitotic score. Pairwise comparisons between racial groups with post-hoc Tukey test identified significant differences in IFN module expression between Black or African American vs. White (p=0.019) and Dendritic cell signature expression between Asian vs White (p=0.047). Among patients in the TNBC subtype, three signatures (dendritic cell signature, macrophage signature and ERBB2 module) were differentially expressed between Black or African American and White patients (p=0.002, 0.016 and 0.007). Conclusion Our analysis demonstrates that among women with high risk breast cancer, race does not affect subtype specific response rates nor event free survival. Distribution of subtypes previously shown to be associated with pCR in the I-SPY2 trial did not significantly differ among racial groups indicating race is less likely than tumor biology to predict response. The decreased expression of immune signatures observed in Black or African American women with TNBC suggests possible differential sensitivity to immunotherapy plus combination chemotherapy. Tumor immune multiplex studies are underway to further investigate. Citation Format: Beverly Kyalwazi, Christina Yau, Olufunmilayo Olopade, A. Jo Chien, Anne Wallace, Andres Forero-Torres, Lajos Pusztai, Erin Ellis, Kathy Albain, Anne Blaes, Barbara Haley, Judy Boughey, Anthony Elias, Amy Clark, Claudine Isaacs, Rita Nanda, Hyo Han, Rachel Yung, Debu Tripathy, Kristen Edmiston, Rebecca Viscusi, Donald Northfelt, Qamar Khan, Ashish Sanil, Scott Berry, Smita Asare, Amy Wilson, Gillian Hirst, Nola Hylton, Michelle Melisko, Jane Perlmutter, Hope Rugo, Fraser Symmans, Laura van ‘t Veer, Donald Berry, Laura Esserman. Analysis of clinical outcomes and expression-based immune signatures by race in the I-SPY 2 trial [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr GS4-02.

9068 Background: The phase 2 SUMMIT basket trial (NCT01953926) demonstrated efficacy of neratinib in patients with EGFR exon 18-mutant NSCLC [Boni et al. WCLC 2020]. Neratinib also has documented activity in HER2+ metastatic breast cancer with CNS metastases [Saura et al. SABCS 2020 & J Clin Oncol 2020]. Here we report neratinib efficacy in a subgroup of patients with EGFR exon 18-mutant NSCLC and CNS involvement from SUMMIT. Methods: Patients with EGFR exon 18-mutant NSCLC were treated with single-agent neratinib (240 mg po daily). Prior EGFR tyrosine kinase inhibitors (TKIs), chemotherapy, and checkpoint inhibitors (IO) were allowed. Patients with stable, asymptomatic CNS metastasis were enrolled. Study endpoints: objective response rate (ORR) at week 8 (±1 week); ORR (RECIST 1.1 confirmed); duration of response (DOR); clinical benefit rate (CBR); progression-free survival (PFS); safety; biomarkers. Results: Baseline characteristics of 11 patients with EGFR exon 18-mutant NSCLC: median age 67 (range 56–83) years; ECOG PS 0/1 (45%/55%). Prior lines of therapies: 2 (range 1–3): EGFR TKIs (91%); chemotherapy (55%); IO (27%). 3/11 patients had baseline CNS metastasis and received radiation 8–22 months prior to study enrollment. Best CNS response in these 3 patients was stable disease with overall individual PFS of 1.9 (censored), 6.9 and 9.1 months and OS of 2.6 (censored), 17.7 (censored), and 17.9 months. Efficacy is summarized in Table. Efficacy summary: TKI-pretreated EGFR exon 18-mutant NSCLC cohort receiving neratinib monotherapy. Conclusions: Activity of single-agent neratinib was observed in prior TKI-exposed patients with EGFR exon 18-mutant NSCLC. Despite the small sample size of only 3 patients with baseline CNS metastases, findings suggest a potential role for neratinib as a systemic treatment option for patients with NSCLC and difficult-to-treat uncommon mutations with CNS involvement. The SUMMIT trial continues to enroll patients with EGFR exon 18-mutant NSCLC. Clinical trial information: NCT01953926. [Table: see text]

PURPOSEThe phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin is a key pathway of survival and therapeutic resistance in breast cancer. We evaluated the pan-Akt inhibitor MK-2206 in combination with standard therapy in patients with high-risk early-stage breast cancer.PATIENTS AND METHODSI-SPY 2 is a multicenter, phase II, open-label, adaptively randomized neoadjuvant platform trial that screens experimental therapies and efficiently identifies potential predictive biomarker signatures. Patients are categorized by human epidermal growth factor receptor 2 (HER2), hormone receptor (HR), and MammaPrint statuses in a 2 × 2 × 2 layout. Patients within each of these 8 biomarker subtypes are adaptively randomly assigned to one of several experimental therapies, including MK-2206, or control. Therapies are evaluated for 10 biomarker signatures, each of which is a combination of these subtypes. The primary end point is pathologic complete response (pCR). A therapy graduates with one or more of these signatures if and when it has an 85% Bayesian predictive probability of success in a hypothetical phase III trial, adjusting for biomarker covariates. Patients in the current report received standard taxane- and anthracycline-based neoadjuvant therapy without (control) or with oral MK-2206 135 mg/week.RESULTSMK-2206 graduated with 94 patients and 57 concurrently randomly assigned controls in 3 graduation signatures: HR-negative/HER2-positive, HR-negative, and HER2-positive. Respective Bayesian mean covariate-adjusted pCR rates and percentage probability that MK-2206 is superior to control were 0.48:0.29 (97%), 0.62:0.36 (99%), and 0.46:0.26 (94%). In exploratory analyses, MK-2206 evinced a numerical improvement in event-free survival in its graduating signatures. The most significant grade 3-4 toxicity was rash (14% maculopapular, 8.6% acneiform).CONCLUSIONThe Akt inhibitor MK-2206 combined with standard neoadjuvant therapy resulted in higher estimated pCR rates in HR-negative and HER2-positive breast cancer. Although MK-2206 is not being further developed at this time, this class of agents remains of clinical interest.

Abstract Background: I-SPY2 is a multicenter, Phase II trial using response-adaptive randomization within biomarker subtypes to evaluate novel agents as neoadjuvant therapy for high-risk at least T2N0 breast cancer. The primary endpoint is pathologic complete response (pCR) at surgery. The goal is to identify regimens that have ≥ 85% Bayesian predictive probability of success in a 300-patient phase 3 neoadjuvant trial defined by hormone-receptor (HR) and HER2 status, and MammaPrint (MP). Regimens may leave the trial for futility (&lt; 10% probability of success), maximum sample size accrual (with probability of success ≥ 10% and &lt; 85%), or as recommended by the independent DSMB. For HER2- subjects the control arm is weekly paclitaxel x12 then doxorubicin & cyclophosphamide (AC) q2-3 weeks x4. For this arm, paclitaxel was omitted and replaced with maximum tolerated dose PARPi talazoparib with synergy dosed irinotecan (25mg/m2). Paclitaxel could be given adjuvantly for these subjects and non-responding subjects could be taken off of experimental therapy. Methods: Women with tumors ≥ 2.5cm were eligible for screening. MP low/HR+ tumors were ineligible. MRI scans (baseline, 3 cycles after start of therapy, prior to AC, and prior to surgery) were used in a longitudinal statistical model to predict pCR for individual patients. Talazoparib was given at 1mg daily with 25mg/m2 irinotecan q2wks. Analysis was intention to treat. Subjects who switched to non-protocol therapy count as non-pCR. Subjects on experimental therapy at time of arm closure are non-evaluable. Talazoparib/irinotecan (TI) was open only to HER2- tumors and eligible for graduation in 3 of 10 pre-defined signatures: HER2-, HR+HER2- and HR-/HER2-. Results: TI did not meet criteria for graduation and was stopped at the recommendation of the DSMB based on expectations of limited activity beyond that seen with standard treatment. Maximum sample size had been reached at the time of this recommendation and subjects currently receiving TI were allowed to continue or change to standard therapy. Exploratory “as treated” analysis for response in gBRCA mutation carriers showed 6/10 gBRCA carriers attained a pCR in the TI arm. Except for 1 patient these gBRCA pCR subjects had &gt;90% tumor reduction by MRI after TI and prior to AC (range: 68-96%). In the TI arm pCR rates were also higher in subjects with a PARPi7-High/MP2 gene expression signature (0.344 vs 0.146). Expected differences in toxicity were seen between arms including g3/4 peripheral neuropathy on control therapy which included paclitaxel (2.6% vs none) and g3/4 neutropenia with TI (30.2% vs 8.2%). Notably gBRCA mutation carriers receiving TI had higher rates of g3/4 neutropenia (60% vs 25.9%). Conclusion: The I-SPY2 study finds the probability that investigational regimens will be successful in a Phase III neoadjuvant trial; TI did not reach the efficacy threshold of 85% probability of success in Phase III in any of the 3 signatures. However by adding talazoparib with synergy dosed irinotecan we were able to omit paclitaxel and observe similar estimated pCR rates. This informs current work to evolve the I-SPY2 trial design to reduce toxicity without compromising outcomes and develop successful combinations targeted to biology, including DNA repair deficiency. Citation Format: Richard Schwab, Amy S. Clark, Christina Yau, Nola Hylton, Wen Li, Denise Wolfe, A Jo Chien, Anne M. Wallace, Andres Forero-Torres, Erica Stringer-Reasor, Rita Nanda, Nora Jaskowiak, Judy Boughey, Tufia Haddad, Heather S. Han, Catherine Lee, Kathy Albain, Claudine Isaacs, Anthony D. Elias, Erin D. Ellis, Payal Shah, Julie E. Lang, Janice Lu, Debasish Tripathy, Kathleen Kemmer, Douglas Yee, Barbara Haley, Melanie Majure, Erin Roesch, Christos Vaklavas, Cheryl Ewing, Teresa Helsten, W Fraser Symmans, Jane Perlmutter, Hope S. Rugo, Michelle Melisko, Amy Wilson, Ruby Singhrao, Laura van 't Veer, Angela DeMichele, Smita Asare, Don Berry, Laura J. Esserman. Evaluation of talazoparib in combination with irinotecan in early stage, high-risk HER2 negative breast cancer: Results from the I-SPY 2 TRIAL [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT136.

Abstract Background: Pathological complete response (pCR) is accepted by FDA as a surrogate endpoint for accelerated approval of targeted agents in combination with chemotherapy based on better long-term outcomes compared to residual disease (Cortazar 2014). Methods: The multi-center, adaptively-randomized I-SPY2 platform trial uses pCR as the primary endpoint to identify investigational agents that will improve outcomes in women with stage 2/3 breast cancer with high risk of early recurrence, across all signatures, based on hormone receptor (HR), HER2, and 70-gene (MammaPrint) status. For patients with HR+ HER2- tumors, only 70-gene (Mammaprint) high-risk patients are enrolled. To date, 1200+ patients have been randomized to one of 14 arms: control (paclitaxel followed by AC); veliparib/carboplatin; neratinib; MK2206; trebananib; trastuzumab/pertuzumab; ado-trastuzumab emtansine/pertuzumab; pembrolizumabx4; ganitumab/metformin; ganetespib; PLX-3397. 7 agents graduated in at least one signature (&gt; 85% probability of success in a 300-patient phase III confirmatory trial); 2 did not graduate; 1 stopped for toxicity, and 3 are enrolling (patritumab/trastuzumab, talazoparib/irinotecan, pembrolizumabx8). Local pathologists were centrally trained using the Residual Cancer Burden (RCB) assessment to ensure uniform evaluation and response classification; RCB 0 = pCR. Results: We evaluated the relationship between pCR and event free (EFS) and distant disease free survival (DDFS) in the first 522 pts (median follow-up:2.5 years). 180 pts achieved pCR (36%) while 338 did not (RCB=1-3). There were 82 EFS and 65 DRFS events. Over the entire group (including all arms), pCR was highly associated with 3-year EFS (p&lt;0.001 for both). Pts achieving pCR had a 3% recurrence risk (RR) at 3 years; those with non-pCR had 24% RR over this time period. For distant recurrence, the 3-year RR with pCR was 2%, compared to 20% in pts with non-pCR. As expected, pCR rates varied by breast cancer subtype (HR+/HER2: 18% (35/196), HR+/HER2+: 40% (33/82), HR-/HER2+:68% (34/50), HR-/HER2-:41% (76/188)). The relationship between pCR and EFS was significant and clinically impactful within each subtype. 3-year survival (pCR group)Hazard Ratio OverallOverallHR+/HER2-HER2+TNBCEFS97%0.08 (0.03-0.23)0.14 (0.02-1.04)0 (NA)0.11 (0.03-0.37)DDFS98%0.08 (0.03-0.26)0.17 (0.01-1.23)0 (NA)0.09 (0.02-0.40) Conclusions: The first long-term efficacy results from the I-SPY2 TRIAL demonstrate that achieving pCR is a very strong surrogate endpoint for improved EFS and DDFS in a high-risk population, across all treatment arms, regardless of subtype. I-SPY2 shows substantially lower estimated EFS hazards for patients achieving pCR, compared to the 5 yr EFS hazard ratio for pCR vs not in Cortazar (hazard ratio 0.49), demonstrating important differences between a metaanalysis compared to a platform trial with uniform high-risk eligibility, standardized pathology assessment, and multiple targeted therapies. Our data support the use of pCR as a primary endpoint for accelerated approval of new drugs if EFS is evaluated in the same population. Based on these findings, the I-SPY2 TRIAL will test whether therapy can be deescalated or escalated for individual patients with the goal of achieving pCR for all. Citation Format: Yee D, DeMichele A, Isaacs C, Symmans F, Yau C, Albain KS, Hylton NM, Forero-Torres A, van't Veer LJ, Perlmutter J, Rugo HS, Melisko M, Chen Y-Y, Balassanian R, Krings G, Datnow B, Hasteh F, Tipps A, Weidner N, Zhang H, Tickman R, Thornton S, Ritter J, Amin K, Klein M, Chen B, Keeney G, Ocal T, Feldman M, Klipfel N, Sattar H, Mueller J, Gwin K, Baker G, Kallakury B, Zeck J, Duan X, Ersahin C, Gamez R, Troxell M, Mansoor A, Grasso LeBeau L, Sams S, Wisell J, Wei S, Harada S, Vinh T, Stamatakos MD, Tawfik O, Fan F, Adams A, Rendi M, Minton S, Magliocco A, Sahoo S, Fang Y, Hirst G, Singhrao R, Asare SM, Wallace AM, Chien AJ, Ellis ED, Han HS, Clark AS, Boughey JC, Elias AD, Nanda R, Korde L, Murthy R, Lang J, Northfelt D, Khan Q, Edmiston KK, Viscusi R, Haley B, Kemmer K, Zelnak A, Berry DA, Esserman LJ. Pathological complete response predicts event-free and distant disease-free survival in the I-SPY2 TRIAL [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr GS3-08.

Abstract Background: Pathologic complete response (pCR) is an established prognostic biomarker for aggressive HER2+ breast cancer (BC). Improving pCR rates may identify new therapies that improve survival. Pertuzumab (P) has established survival benefit in the metastatic setting, and received accelerated approval in the neoadjuvant setting when combined with trastuzumab (H) and docetaxel(D) as part of a complete treatment regimen for early breast cancer. We tested its ability, when combined with standard therapy (paclitaxel, T, and H) to improve pCR (ypT0ypN0) over TH in the adaptively randomized, phase II, I-SPY 2 neoadjuvant trial. Methods: Enrolled patients (pts) had invasive BC ?2.5 cm in HER2-positive subsets. Pts were adaptively randomized to control (TH, qwk x 12) or THP (P, q3wk x 4) followed by doxorubicin/cyclophosphamide (AC) x 4 and surgery. To compare THP to TH we utilized all control pts accrued over the course of the trial, adjusting for potential differences due to time period treated, which were informed by the several other treatment arms that have been in the trial. Adaptive assignment to the experimental arms was based on current Bayesian probabilities of superiority over control. “Graduation” by signature and futility stopping were based upon Bayesian predictive probability of success in a 2-arm, N = 300 phase III randomized 1:1 trial of THP vs. TH with pCR endpoint. Results: THP met the predictive probability criterion and graduated in 3 signatures: all HER2+, HER2+/HR+, and HER2+/HR- (See Table 1). Final accrual: 44 THP and 31 TH. Safety data will be shown. Conclusions: I-SPY 2's standing platform trial efficiently evaluates agents in biomarker-defined pt subsets. THP -&gt; AC substantially improves pCR rates over standard TH -&gt; AC in all 3 HER2+ signatures, including HR+ and HR- subsets. APHINITY, a trial of adjuvant pertuzumab with a primary outcome of invasive disease-free survival, is ongoing. Table 1Signature*Estimated pCR Rate (95% probability interval)Signature*THPControl (TH)Probability THP Is Superior to ControlPredictive Probability of Success in Phase IIIHER2+54% (38%-70%)22% (5%-39%)99.8%96%HER2+/HR+44% (24%-63%)17% (0%-34%)99%91%HER2+/HR-74% (53%-95%)33% (6%-59%)99.8%98%*HR = Hormone Receptor Citation Format: Meredith Buxton, Angela M. DeMichele, Stephen Chia, Laura van't Veer, Jo Chien, Anne Wallace, Henry Kaplan, Julie Lang, Douglas Yee, Claudine Isaacs, Stacy Moulder, Kathy Albain, Judy Boughey, Kathleen Kemmer, Barbara Haley, Susan Minton, Andres Forero, Rita Nanda, Anthony Elias, Larissa Korde, Rebecca Viscuzi, Hope Rugo, Richard Schwab, Fraser Symmans, Melissa Paoloni, Nola Hylton, Michael Hogarth, Julia Lyandres, Jane Perlmutter, Ashish Sanil, Christina Yau, Laura Esserman, Don Berry, I-SPY 2 TRIAL Investigators. Efficacy of pertuzumab/trastuzumab/paclitaxel over standard trastuzumab/paclitaxel therapy for HER2+ breast cancer: Results from the neoadjuvant I-SPY 2 TRIAL. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT106.

Abstract Background: Pathologic complete response (pCR) is an established prognostic biomarker for aggressive HER2+ breast cancer (BC). Improving pCR rates may identify new therapies that improve survival. T-DM1 and pertuzumab have established benefits in metastatic HER2+ BC. We tested their ability when combined, without paclitaxel, to improve pCR rates (ypT0ypN0) over standard therapy in the randomized, phase 2, I-SPY 2 neoadjuvant trial. Methods: Enrolled patients (pts) had invasive breast cancer ?2.5 cm in HER2-positive subsets. Pts were adaptively randomized to 12 wkly cycles of paclitaxel+trastuzumab (TH, control) or T-DM1+pertuzumab (T-DM1+P) without T, followed by doxorubicin/cyclophosphamide (AC) x 4 and surgery. We utilized all TH control pts accrued over the course of the trial, adjusting for potential differences due to time period treated, which were informed by the several other treatment arms that have been in the trial. Adaptive assignment to the various experimental arms in the trial was based on current Bayesian probabilities of superiority vs. control. “Graduation” by signature and futility stopping were based upon Bayesian predictive probability of success in a future 2-arm, N = 300 neoadjuvant Phase 3 randomized 1:1 trial of T-DM1+P vs. control with pCR endpoint. Results: T-DM1+P met the predictive probability criterion and graduated from I-SPY 2 in 3 signatures: all HER2+, HER2+/HR+, HER2+/HR- (Table 1). Final accrual: 52 T-DM1+P and 31 TH. Safety data will be shown. Conclusions: I-SPY 2's standing platform trial mechanism efficiently evaluates agents in biomarker-defined pt subsets. T-DM1+P (w/o T) -&gt; AC substantially improves pCR rates over standard TH -&gt; AC in all 3 HER2+ signatures, including HR+ and HR- subsets. These findings warrant further investigation of these agents without paclitaxel in a neoadjuvant trial powered for survival endpoints. Table 1Signature*Estimated pCR Rate (95% probability interval)Probability T-DM1+P Is Superior to Control**Predictive Probability of Success in Phase 3T-DM1+PControl (TH)HER2+52% (36%-68%)22% (5%-39%)99.5%94%HER2+/HR+46% (26%-66%)17% (0% - 34%)99.1%93%HER2+/HR-64% (39%-88%)33% (6%-59%)98%90%*HR = Hormone Receptor Citation Format: Angela M. DeMichele, Stacy Moulder, Meredith Buxton, Douglas Yee, Anne Wallace, Jo Chien, Claudine Isaacs, Kathy Albain, Judy Boughey, Kathleen Kemmer, Barbara Haley, Julie Lang, Henry Kaplan, Susan Minton, Andres Forero, Anthony Elias, Rita Nanda, Larissa Korde, Richard Schwab, Michelle Melisko, Ashish Sanil, Michael Hogarth, Nola Hylton, Melissa Paoloni, Fraser Symmans, Jane Perlmutter, Julia Lyandres, Christina Yau, Don Berry, Laura Esserman, I-SPY 2 TRIAL Investigators. Efficacy of T-DM1+pertuzumab over standard therapy for HER2+ breast cancer: Results from the neoadjuvant I-SPY 2 TRIAL. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT042.