Moreno‐Aspitia, Alvaro

Abstract Background: Targeting immune checkpoint programmed death receptor 1 (PD-1)/PD-L1 pathway has shown promising clinical activity with some preliminary association of clinical benefit with PD-L1 expression on tumors. Recent preclinical and clinical studies highlight the beneficial immunomodulatory potential of epigenetic therapy. Entinostat is a class I specific histone deacetylase inhibitor (HDACi). A promising preclinical study showed that entinostat in combination with immune checkpoint blockade agent can eradicate modestly immunogenic breast tumors in mice via reduction in immunosuppressive myeloid-derived suppressor cells. In this study, we investigated the effects of entinostat on expression of immune-related genes in breast cancer cells to further explore the potential mechanism of its combined activity. Method: Gene expression was assessed on Nanostring platform using the nCounter GX Human ImmunologyV2 panel comprised of 594 immune-related and 15 reference genes. Gene expression was normalized to the internal positive controls and reference genes using nSolver2.0 software. Hormone receptor-positive (HR+) breast cancer (MCF-7 and T47D) and triple negative breast cancer (TNBC) cell lines (MDA-MB-231 and Hs578T) were used for the analysis. Gene expression analysis was performed on control and after 24-hour treatment of entinostat at clinically relevant 125 and 500 nM concentrations. Results: Overall, a greater number of immune-related genes were induced > 2 fold with entinostat at 125 and 500 nM in TNBC compared to HR+: 77 and 118 genes in MDA-MB-231, 80 and 147 genes in Hs578T, 20 and 64 genes in MCF-7, and 73 and 72 genes in T47D, respectively. In particular, MHC class I (HLA-A, HLA-B, HLA-C) and II (HLA-DMA, HLA-DMB, HLA-DOA, HLA-DOB, HLA-DPA1, HLA-DPB1, HLA-DQA1, HLA-DQA2, HLA-DQB1, HLA-DQB2, HLA-DRA, and HLA-DRB1) genes were induced by entinostat in a dose dependent manner (range 1.5-22.44 fold). These inductions were observed in both HR+ and TNBC cell lines. Interestingly, we found higher baseline expression and a several fold increase in PD-L1 expression in TNBC. PD-L1 mRNA expression increased by 1.74 and 2.14 fold in MDA-MB-231 and 3 and 9.6 fold in Hs578T with 125 and 500 nM treatment, respectively. Corresponding increase in PD-L1 protein expression after entinostat treatment was also observed. In contrast, there appeared to be no significant changes in PD-L1 expression after entinostat treatment in MCF-7 and T47D. Furthermore, we also identified 21 genes that were differentially induced by entinostat in TNBC but not in HR+. These genes include PTPN22, ARG2, CISH, IL17A, ICAM2, KIR3DL1, CXCR3, TLR2, CFD, CCR5, IL13, LILRA3, IL8, TNFRSF9, DPP4, MR1, SELPLG, PTGS2, IL1B, CD3D, and MBL2. No significant change in PDL2 expression was observed in any of the cell lines. Conclusion: Our data suggest that entinostat induces immune-related genes involved in antigen presentation in both ER+ and TNBC cells, potentially increasing the immunogenicity of these tumors. Given the significant induction of PD-L1 expression with entinostat in TNBC, our preclinical data provides support for further investigation of entinostat in combination with anti-PD1 or anti-PD-L1 in this subtype of breast cancer. Citation Format: Chumsri S, Necela BM, Ordentlich P, Advani P, Moreno-Aspitia A, McLaughlin SA, Geiger X, McDonough M, Vallow LA, Perez EA, Thompson EA. Immunomodulatory effects of entinostat on PD-L1 and MHC class I and II in different subtypes of breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-04-02.

PurposeWe compared nab-paclitaxel or ixabepilone once per week to paclitaxel with bevacizumab as first-line therapy for patients with advanced breast cancer (BC) to evaluate progression-free survival (PFS) for nab-paclitaxel or ixabepilone versus paclitaxel.Patients and MethodsEligible patients were age ≥ 18 years with chemotherapy-naive advanced BC. Patients were randomly assigned to bevacizumab with paclitaxel 90 mg/m2(arm A), nab-paclitaxel 150 mg/m2(arm B), or ixabepilone 16 mg/m2(arm C), once per week for 3 of 4 weeks. Planned enrollment was 900 patients, which would give 88% power to detect a hazard ratio of 0.73.ResultsIn all, 799 patients were enrolled, and 783 received treatment (97% received bevacizumab). Arm C was closed for futility at the first interim analysis (n = 241), and arm A (n = 267) and arm B (n = 275) were closed for futility at the second interim analysis. Median PFS for paclitaxel was 11 months, ixabepilone was inferior to paclitaxel (PFS, 7.4 months; hazard ratio, 1.59; 95% CI, 1.31 to 1.93; P < .001), and nab-paclitaxel was not superior to paclitaxel (PFS, 9.3 months; hazard ratio, 1.20; 95% CI, 1.00 to 1.45; P = .054). Results were concordant with overall survival; time to treatment failure was significantly shorter in both experimental arms v paclitaxel. Hematologic and nonhematologic toxicity, including peripheral neuropathy, was increased with nab-paclitaxel, with more frequent and earlier dose reductions.ConclusionIn patients with chemotherapy-naive advanced BC, ixabepilone once per week was inferior to paclitaxel, and nab-paclitaxel was not superior with a trend toward inferiority. Toxicity was increased in the experimental arms, particularly for nab-paclitaxel. Paclitaxel once per week remains the preferred palliative chemotherapy in this setting.

Abstract INTRODUCTION Next generation sequencing (NGS) of patients has significantly changed our ways to study cancer genomics as it provides precise estimates of gene expression, fusion transcripts, expressed single nucleotide variants (eSNVs), splice variants and copy number variants. The Breast Cancer Genome Guided Therapy (BEAUTY) is an ongoing clinical study in which RNA sequencing (RNAseq) and whole exome sequencing (WES) are performed prior to, during and after neoadjuvant chemotherapy. Here we report the use of these sequencing technologies to investigate gene expression levels and mutational profiles in a triple negative breast cancer (TNBC) patient enrolled in BEAUTY whose disease did not respond to neoadjuvant paclitaxel and anthracycline/cycphosphamide. METHODS Computational approaches were used to integrate WES and RNAseq data obtained before therapy (V1T), after 12 weekly paclitaxel treatments (V2T) and after anthracycline-based regimen at surgical resection (V3T) to study a single patient with persistent TNBC disease after neoadjuvant chemotherapy. RESULTS Using RNA-Seq data, we identified an inter-chromosomal fusion transcript between chromosome 20 and 22 (GNAS-TTC38) that was highly expressed at V1T, V2T and V3T. We also identified intra-chromosomal fusion transcripts that were expressed at two time points, such as fusion transcript (KANSL1-ARL17A) on chromosome 17 for V1T and V2T and fusion transcript (RBM12B-LINC00535) on chromosome 8 for V2T and V3T time points. Several gene expression changes were also observed. Gene expression analysis of V1T, V2T and V3T tumors was performed. Differential temporal gene expression profiles of 9884 genes that were significant and varying at different time points were obtained for pathway analysis. Pathway analysis of 9884 genes identified up regulation and down regulation of several transcription factors with a fold change of 2x or more. When compared to blood, DNA tumor and RNA-Seq data, we identified 81 common somatic eSNVs that were expressed in both V1T and V2T time points and we are in the process of investigating V3T data. We found alterations of key transporter domains (CD225, Coatamer_beta_C, DUF2435, Dynamitin, EI24, GLTP, LMF1, Porin_3, V-ATPase_C) in our V1T and V2T SNV data. Similar to gene expression analysis, we are in the process of obtaining the list of mutations at various time points to identify driver and passenger mutation candidate genes for this specific TNBC patient. CONCLUSIONS Our initial time-series analysis of eSNV, fusion transcripts and gene expression data demonstrate that intensive analysis for individual patients is feasible. Further investigation of drug transporters and transcription regulators may help develop personalized treatment strategies for patients with disease resistant to current regimens. Citation Format: Krishna R. Kalari, Xiaojia Tang, Kevin J. Thompson, Douglas W. Mahoney, Poulami Barman, Jason P. Sinnwell, Hugues Sicotte, Peter Vedell, Steven N. Hart, Travis J. Dockter, Katie N. Jones, Amy L. Conners, Ann M. Moyer, Daniel W. Visscher, Jia Yu, Bowen Gao, Sarah A. McLaughlin, John A. Copland, Alvaro Moreno-Aspitia, Donald W. Northfelt, Richard J. Gray, Vera J. Suman, Jeanette E. Eckel Passow, Jean-Pierre A. Kocher, Eric D. Wieben, Gianrico Farrugia, Cloann G. Schultz, James N. Ingle, Richard Weinshilboum, Matthew P. Goetz, Liewei Wang, Judy C. Boughey. Analysis of sequencing data to identify potential drug targets for an individual newly diagnosed with basal breast cancer who failed to respond to current standard neoadjuvant chemotherapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4185. doi:10.1158/1538-7445.AM2014-4185

Abstract Background Cancer genomic investigations have identified recurrent genomic aberrations critical for cancer initiation, progression, and metastases. However, these investigations are typically performed in isolation, and the effects of treatment on the clonal selection of tumor cells are mostly unknown. We hypothesized that molecular profiling of residual tumors after neoadjuvant chemotherapy (NAC) would identify new drug targets/pathways in patients at high risk for disease recurrence. To better identify clonal populations of resistant breast cancer cells, we utilized DNA content-based flow sorting of nuclei to identify and isolate clonal populations for aCGH and next generation sequencing (NGS) both before and after NAC. Methods The Breast Cancer Genome Guided Therapy Study (BEAUTY) (NCT 02022202) is a prospective study of patients with high-risk breast cancer treated with neoadjuvant 12 weekly paclitaxel (T) +/- trastuzumab followed by 4 cycles of anthracycline based chemotherapy. Tumor tissue from baseline, residual disease from surgery, distant metastases, and patient derived xenografts (PDX) are obtained for cell sorting by DNA ploidy, aCGH, RNA and exome sequencing. Results: 140 patients have been enrolled, 104 have completed surgery and 30 unique PDX have been established corresponding to 26 patients prior to chemotherapy and 4 from residual disease at surgery. Baseline exome and RNA sequencing is complete in 140. Currently, genomic analyses of flow sorted matched baseline, surgical, PDX, and distant disease samples are available in 6 patients. Substantial genomic variation was observed in the surgical sample compared to the primary tumor including gain of oncogenic drivers (EGFR) and loss of negative regulators (ATG5) (Table). The PDX recapitulated these events with excellent fidelity compared to the corresponding human tumor. In patients with TNBC, RNA seq obained from matched samples demonstrated changes in immune related pathways. Evaluation of drug targets/pathways identified in the resistant tumors are ongoing using the PDX and sequencing of the remaining matched baseline/surgical disease will be reported. Clonal changes occurring over time in patients with residual disease or disease recurrence after NACTumor SubtypeResidual Cancer BurdenDisease StatusClonal Aberration Changes (baseline and post NAC)TNBC (AR subtype)3Contralateral lymph node recurrence at 150 days2p25.2 - p25.1 amplicon lost at recurrence; 6p21.32 -p21.31 amplicon lost at recurrenceTNBC (BL 1)3Bone/liver/lymph node recurrence at 135 days5q11.2 amplicon gained at surgery; 12p13.33 - p13.2 amplicon gained at surgeryTNBC (BL 1)3Disease-free at day 1506q21 amplicon lost at sugeryTNBC (BL 2)0Brain recurrence at 390 daysChr 2 chromothripsis at surgeryLuminal B3Progression during chemotherapy7p12.1 - p11.2 amplicon gained at surgeryLuminal HER23Disease-free at day 3609q33.2 amplicon lost at surgery; 15q13.1 - q13.3 amplicon lost at surgery; 15q22.2 - q24.1 amplicon lost at surgery Conclusions: We observed substantial evolutionary changes in residual breast tumors remaining after NAC. Our findings suggest that a comprehensive assessment of the mutational landscape that has evolved during NAC can inform drug development in high risk breast cancer patients. Citation Format: Matthew P Goetz, Michael T Barrett, Krishna R Kalari, Vera J Suman, Sarah A McLaughlin, Alvaro Moreno-Aspitia, Ann M Moyer, Donald W Northfelt, Richard J Gray, Jason Sinnwell, Douglas Mahoney, Poulami Barman, Peter Vedell, Xiaojia Tang, Kevin Thompson, Travis Dockter, Katie Jones, Sara J Felten, Amy Conners, Jeanette Eckel-Passow, Hughes Sicotte, Steven N Hart, Jia Yu, Daniel W Visscher, Eric D Wieben, Cloann Schultz, Minetta C Liu, James N Ingle, Liewei Wang, Richard W Weinshilboum, Judy C Boughey. Impact of neoadjuvant chemotherapy on the clonal composition of breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr PD3-3.

Abstract Background: TNBC is characterized by unique molecular profiles, aggressive behavior, poor prognosis and lack of targeted therapies. Brostallicin is a novel synthetic compound from the class of DNA minor groove binding (MGB) anti-cancer agents, making it a logical agent to evaluate in the setting of TNBC. It retains activity in cancer cells resistant to alkylating agents, topoisomerase I inhibitors and is fully active against DNA-mismatch repair deficient tumor cells. Preclinical models using cell lines demonstrate that cells expressing relatively high glutathione/glutathione S-transferase (GSH/GST) levels are more susceptible to brostallicin's antitumor efficacy. Cisplatin administration increases expression of GSH/GST in tumor cells, thus leading to an increased anti-tumor efficacy of brostallicin. Methods: Phase II cooperative group study in pts with mTNBC (³18 years of age with measurable metastatic disease, ER/PR ≤1%; HER2 negative, who had received 0–4 prior chemotherapy regimens in the metastatic setting; with adequate hematologic, renal and hepatic functions; and no active CNS metastases; prior exposure to cisplatin allowed). Cisplatin on Day 1 followed by brostallicin on Day 2, repeated every 21 days. Aim: efficacy of brostallicin and proof of concept of its mechanism of action in mTNBC. Primary endpoint progression-free survival (PFS) at 3 months with 89% power (0.10 significance level) to detect an absolute difference of 20% (35% vs 55%), based on the median PFS of 60 days in pts with mTNBC from the N0234 trial of erlotinib and gemcitabine as 1st/2nd line. Secondary endpoints include ORR, duration of response (DOR), 6-month PFS, OS and AE profile. Tertiary endpoints include assessment of 1) GSH levels prior to the administration of cisplatin and of brostallicin; and 2) the prevalence of BCRA-1 mutation by IHC in primary or metastatic tumor. Results: Study closed on 3/28/12 and it accrued 48 pts (median f/u 2.3 mo; 0–15.3); 33 pts are off treatment and 15 pts remain on study; 38 pts evaluable for response, and 43 evaluable for AEs. 50% received therapy as 3rd to 5th line. Median number of cycles 2.5 (off-treatment: 2; on-treatment: 3, range 0–15). There are currently 5 confirmed responses (4 PR and 1 CR); DOR: 2.8–13.3 months. The 6-mo PFS is currently 19.2% (95% CI: 8.9%, 41.3%); the median TTP is 3.0 months (95% CI: 1.7 months, 4.2 months). Current data are premature to determine the primary endpoint (3-mo PFS) but we expect to report such data by November 2012. Current toxicity data: 69.7% G3/4 heme toxicity. Non-heme toxicity G3 (30.2%) and G4 (9.3)% (febrile neutropenia 21%; fatigue G3 14%); and no G5 non-heme AE. Conclusions: The current preliminary data of this trial show very encouraging activity of this regimen (brostallicin plus cisplatin) in mTNBC. Near 1/3 of pts are still currently receiving therapy, and we expect to provide primary and additional secondary endpoint data at SABCS 2012. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-12-06.

Abstract Background: Based upon the association between pathologic response and disease free survival, the neoadjuvant setting is increasingly being used for drug development. NGS has identified unique and recurrent genetic alterations in breast cancer (BC) that are potentially targetable; however, the clinical implications are mostly unknown. We developed a prospective neoadjuvant study (BEAUTY) in high risk BC patients (pts) using weekly T followed by anthracycline-based chemo wherein percutaneous tumor biopsies (PTB) are obtained before/during/after chemo for NGS and PDX. Our goal is to identify novel biomarkers/pathways and develop PDX to test new therapeutic approaches. Methods: Pts underwent PTB at baseline and after 12 wks of T. Response to T was defined based upon 12 week Ki-67: responder (&lt;15%) vs non-responder (≥15%). Pts with histologic response and absence of invasive BC at 12 wks were classified as responders. NGS was performed using PTB/blood DNA (exome) and PTB (RNA seq). MRI response was classified using RECIST criteria. NGS data were used to identify somatic copy number variants (cnvs) and expressed single nucleotide variants (eSNVs). Non-SCID mice (estrogen supplemented) were implanted ≤ 30 minutes with PTB samples. Results: Of the first 78 pts, 44 have completed T. Here we focus on 18 pts with either triple negative or luminal B BC. Clinical characteristics according to Ki-67 response are shown in Table 1. Comparison of genomic alterations in BEAUTY pts with TCGA identified a greater overlap with copy number gains (73%) compared to deletions (40%), along with similar observations of mutations in TP53, PTEN, RYR2, and AKT1 genes. Association analysis of CNVs and eSNVs between responders/non-responders identified 33 genes (predominantly located in chromosomes 1, 8, 13) and 580 eSNVs (corresponding to 497 genes) with a p &lt; 0.05. Differential gene expression (DGE) analysis of responders/non-responders identified 198 genes with a p-value &lt; 0.05. Integrated analysis of 539 genes (CNVs, eSNVs and DGE) identified pathways such as TGF-beta, Jak-Stat, WNT and NOTCH signalling. PDX take rate was 44% [triple negative (6/10); Luminal B (2/8)]. PDX growth rate was significantly associated with clinical baseline Ki-67 (p = 0.00014). Conclusion: This is the first prospective study to demonstrate the feasibility of using PTB to obtain both NGS data and PDX in the neoadjuvant setting. PDX take rate is associated with BC subtype and baseline Ki-67. Studies are ongoing to 1) validate genes/pathways associated with treatment response in subsequent BEAUTY pts; 2) genomically characterize and assess PDX in vivo response to T and 3) Use NGS data to prioritize new drugs/drug combinations in PDX. Funded by Mayo Clinic Center for Individualized Medicine and MC Cancer Center. Clinical CharacteristicsOverallResponders: 12 week Ki-67 &lt; 15% (n = 9)Non-Responders: 12 week Ki-67 ≥ 15% (n = 9)Median Age495345T stage T2/T314 (78%)7 (78%)7 (78%)Node Positive8 (44%)4 (44%)4 (44%)Triple negative10 (56%)6 (67%)4 (44%)Luminal B8 (44%)3 (33%)5 (56%)Ki-67 after 12 Weeks of T Median 5% (0-11%)Median 35% (17-60%)Complete/Partial MRI Response after T 6 (67%)2 (22%) Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-08-10.

BACKGROUNDIncreased soluble human epidermal growth factor receptor 2 (sHER2) is an indicator of a poor prognosis in HER2‐positive metastatic breast cancer. In this study, the authors evaluated levels of sHER2 during treatment and at the time of disease recurrence in the adjuvant North Central Cancer Treatment Group N9831 clinical trial.METHODSThe objectives were to describe sHER2 levels during treatment and at the time of recurrence in patients who were randomized to treatment arms A (standard chemotherapy), B (standard chemotherapy with sequential trastuzumab), and C (standard chemotherapy with concurrent trastuzumab). Baseline samples were available from 2318 patients, serial samples were available from 105 patients, and recurrence samples were available from 124 patients. The cutoff sHER2 value for the assay was 15 ng/mL. Statistical methods included repeated measures linear models, Wilcoxon rank‐sum tests, and Cox regression models.RESULTSThere were differences between groups in terms of age, menopausal status, and hormone receptor status. Within treatment arms A, B, and C, patients who had baseline sHER2 levels ≥15 ng/mL had worse disease‐free survival than patients who had baseline sHER2 levels <15 ng/mL (arm A: hazard ratio, 1.81; P = .0014; arm B: hazard ratio, 2.08; P = .0015; arm C: hazard ratio, 1.96; P = .01). Among the 124 patients who experienced disease recurrence, sHER2 levels increased from baseline to the time of recurrence in arms A and B but remained unchanged in arm C. Patients who had recurrence sHER2 levels ≥15 ng/mL had a shorter survival after recurrence with a 3‐year overall survival rate of 51% compared with 77% for those who had recurrence sHER2 levels <15 ng/mL (hazard ratio, 2.36; 95% confidence interval, 1.19‐4.70; P = .01).CONCLUSIONSIn patients with early stage, HER2‐positive breast cancer, a high baseline sHER2 level was identified as a prognostic marker associated with shorter disease‐free survival, and a high sHER2 level at recurrence was predictive of shorter survival. Cancer 2013;119:2675–2682. © 2013 American Cancer Society.

BACKGROUNDData suggest that weight, and specifically body mass index (BMI), plays a role in breast cancer development and outcome. The authors hypothesized that there would be a correlation between BMI and clinical outcome in patients with early stage, human epidermal receptor 2 (HER2)‐positive breast cancer enrolled in the N9831 adjuvant trial.METHODSPatients were grouped according to baseline BMI as follows: normal (BMI <25 kg/m2), overweight (BMI ≥25 kg/m2 and <30 kg/m2), and obese (BMI ≥30 kg/m2). Disease‐free survival (DFS) was estimated using the Kaplan‐Meier method. Comparisons between treatment arms A, B, and C (chemotherapy with or without trastuzumab) were performed using a stratified Cox proportional hazards model.RESULTSAnalysis was completed on 3017 eligible patients. Obese patients were more likely to be older and postmenopausal (P < .0001 for both), to have larger tumors (P = .002), and to have positive lymph nodes (P = .004). In the pooled analysis cohort, differences in DFS among the BMI groups were statistically significant (5‐year DFS rate: 82.5%, 78.6%, and 78.5% for normal weight, overweight, and obese women, respectively; log‐rank P = .02). The adjusted hazard ratio comparing the DFS of overweight women with the DFS of normal women was 1.30 (95% confidence interval, 1.06‐1.61); and, comparing the DFS of obese women with the DFS normal women, the adjusted hazard ratio was 1.31 (95% confidence interval, 1.07‐1.59). There were no statistically significant differences in DFS by weight group for women within any trial arm.CONCLUSIONSPatients with early stage, HER2‐positive breast cancer and normal BMI had a better 5‐year DFS compared with overweight and obese women. The current results indicated that adjuvant trastuzumab improves clinical outcome regardless of BMI. Cancer 2013;119:2447‐2454. © 2013 American Cancer Society.

Abstract Background Obesity, as defined by body mass index (BMI), has been associated with increased recurrence rate, shorter DFS and increased death rates due to breast cancer (BC). Most of the studies to date have examined the relationship of BMI and DFS in patients with hormone receptor positive disease. To our knowledge, BMI and its relationship with outcome in early stage HER2 positive breast cancer has not previously been examined. The N9831 is a large phase III trial testing the role of trastuzumab in the adjuvant setting of high risk patients with early stage HER2+ BC. We hypothesized that the occurrence of overweight and obesity may correlate with outcome. Methods: This analysis presents BMI and its relation to tumor characteristics and DFS in patients (pts) enrolled in the N9831 clinical trial. Pts were categorized as normal weight, overweight or obese using the WHO BMI classification parameters of &lt; 25%, 25–29% and ≥ 30% respectively. For patient characteristics, patients were grouped into non-obese (BMI&lt; 30) and obese (≥ 30) cohorts. DFS was estimated by the Kaplan-Meier method. Comparisons between arms A (chemotherapy alone), B (chemotherapy plus sequential trastuzumab) and C (chemotherapy plus concurrent trastuzumab) were performed using the Cox proportional hazards model, stratified by BMI. Results: Analysis was completed on 3,017 eligible pts. Obese pts were more likely to be older and postmenopausal (p&lt;0.0001 for both). There was no significant association between BMI and ER/PR status (p=0.07) or histologic tumor grade (p=0.33). Obese pts were found to have significantly larger tumors ≥ 2 cm (p=0.002) and more positive lymph nodes (p=0.02). There was no significant difference in DFS within each intrinsic arm (A, B and C) between the obese and non-obese pts at 3, 5 or 7 yrs of follow up. However, pts in the non-obese group had significantly improved DFS in arm B and C compared to arm A (p=0.001 and p&lt;0.0001 respectively). Also obese pts in arm C had significantly improved DFS compared to obese pts in arm A (p=0.008). There was a trend of improved DFS in the obese group in arm B compared to arm A, but this was not statistically significant (p=0.09). Pts in the normal weight and overweight groups did significantly better in arm B (p=0.02 for both) and arm C (p=0.01 and p=0.002 respectively) compared to arm A. Conclusions: This analysis of data from the N9831 study confirms that obese pts with early stage HER2+ tumors have worse clinical outcome than pts with BMI &lt; 30%. Adjuvant trastuzumab improved clinical outcome regardless of BMI. This study supports weight loss intervention for obese women with early stage HER2+ BC. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-12-02.