Perez, EA

Abstract Background: Adding adjuvant trastuzumab to chemotherapy for patients (pts) with resected HER2+ breast cancer (BC) improves disease free and overall survival (Perez EA, et al. J Clin Oncol 2011). Understanding which pts are most likely to benefit from these therapies is a goal of our team. Methods: Baseline 1639 annotated tumor specimens from pts enrolled in the phase III N9831 adjuvant trastuzumab trial (NCT00005970) were processed via the >29,000 gene probe DASL technology (Illumina) to identify genomic predictors of pt outcome to Arm A chemotherapy or Arm C chemotherapy plus concurrent trastuzumab. Samples were spotted in 96 well plates, with appropriate replicates. Extensive quality control and internal validation were performed. The association of each gene with recurrence-free survival (RFS) was determined for each treatment arm separately using CoxPH models adjusted for clinical and tumor risk factors. A p < 0.0001 was used to define significance. A geneset analysis (using 408 Kegg/BioCarta genesets) was performed to determine pathways associated with RFS. Results: PRPF4B, EWSR1, BMI1, CNNM1, FOXO4, CLIP2, MCCC1, CHRM2 were found to be significantly associated with RFS for Arm A and AAK1, DAZAP2, TP53INP1, MACF1 and ADHFE1 were associated with RFS for Arm C. The most significant pathway associated with RFS in Arm A was the KEGG hypertrophic cardiomyopathy pathway and for Arm C, the BioCarta pertussis toxin-insensitive CCR5 signaling in macrophage pathway. Conclusions: We have identified 8 genes associated with RFS for pts treated with adjuvant chemotherapy, and 5 genes associated with RFS for pts treated with concurrent trastuzumab and chemotherapy in pts with HER2 early stage BC. In addition, geneset analysis identified BioCarta and Kegg pathways associated with RFS for each arm. Validation in an independent cohort is expected to be completed by the end of 2012. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD10-04.

Abstract Background: Intrinsic breast cancer subtypes determined by the PAM50 assay are reported to be prognostic independent of standard clinicopathological variables. The CALGB (Alliance) 9741 adjuvant trial randomized treatment in a 2×2 factorial design to (i) 2-wk (dose dense; DD) vs 3-wk therapy and (ii) sequential vs concurrent doxorubicin, cyclophosphamide, paclitaxel (A>T>C vs AC>T). DD therapy improved disease-free survival and overall survival (OS) (Citron et al. JCO 2003.). A significant interaction between intrinsic breast cancer subtypes and the use of DD therapy was hypothesized. Methods: C9741 was conducted in collaboration with ECOG, NCCTG, and SWOG. Biospecimens were collected from 1652 of 2005 subjects. Multiplexed gene expression profiling (NanoString Technologies, Inc) generated PAM50 subtype calls (luminal A, luminal B, HER2-enriched, basal-like), risk of relapse (ROR) score, and proliferation score for 1321 cases (80%). Excluded samples were due to insufficient tumor (n = 181) or RNA (n = 150). The primary endpoint was relapse-free survival (RFS). The primary analysis to determine if the clinical benefit of DD therapy is dependent on intrinsic subtype was conducted as a test of interaction in a Cox proportional hazards model (3 degrees of freedom, df; alpha=0.05). Similar analyses were performed for ROR score and proliferation score as continuous measures of risk (1 df). PAM50 subtype, ROR score, and proliferation score were evaluated in separate multivariate models adjusting for number of positive nodes, menopausal status, dose density, and sequence of therapy. Results: Improved outcomes for DD therapy in the evaluable subset mirrored results from the complete dataset (HR = 1.20; 95%CI 0.99–1.44) with a median follow-up of 12.3 yrs. Subtype analysis identified 32% luminal A (n = 417), 26% luminal B (n = 341), 20% HER2-enriched (n = 267), and 22% basal-like (n = 296). Intrinsic subtypes were prognostic of RFS (p < 0.0001) irrespective of treatment assignment with HRs relative to the luminal A subgroup of 1.50 (luminal B), 1.70 (HER2-enriched) and 1.66 (basal-like). No subtype specific treatment effect on RFS was identified (p = 0.44). ROR scores (range 0–100, median 60) were also prognostic of RFS (HR = 1.12 for a 10-unit change; 95% CI 1.07–1.18; p < 0.0001), but no association with DD therapy benefit was seen (p = 0.58). Similar results were obtained for the proliferation score, for OS as a secondary endpoint, and from multivariate models with clinical covariates. Conclusion: The prognostic value of PAM50 subtype, ROR score, and proliferation score remains highly significant in patients treated with contemporary adjuvant anthracycline and taxane based chemotherapy. Intrinsic subtype did not predict for improved survival with the 2-wk DD vs 3-wk treatment schedule; we hypothesize that this is because the prognostic differences by subtype outweighed the modest but significant clinical benefit of DD chemotherapy administration for the overall population. Planned clinical validation studies will assess the ability of PAM50 and other gene signatures to stratify patients and individualize systemic therapy regimens based on the expected risk of distant recurrence. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-10-01.

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 Epigenetic silencing of tumor suppressing genes by promoter-specific DNA methylation is common in many types of cancer. As an early event, this process has been well shown to promote tumor initiation and progression; however little is known how such epigenetic silencing can contribute to tumor metastasis. The PRKD1 gene encodes Protein Kinase D1 (PKD1), a serine/threonine kinase expressed in epithelial cells of the normal mammary gland that maintains the epithelial phenotype of normal breast cells and prevents epithelial-to-mesenchymal transition (EMT). PKD1 is also a critical suppressor of tumor cell invasion and is silenced in expression and activity during breast tumor progression. Here, we show that aberrant methylation of PRKD1 promoter region is not only correlated with the silencing of its expression but is also associated with invasiveness of breast cancer cell lines and with aggressiveness of breast tumors. Using the highly invasive MDA-MB-231 cells, we show that the inhibition of PRKD1 promoter methylation with the DNA methyltransferase inhibitor decitabine restores PKD1 expression and significantly decreases their invasive abilities in vitro. More importantly, in a tumor xenograft model it dramatically blocks tumor spread and metastasis to the lung in a PKD1-dependent fashion. Our data suggest that the status of epigenetic regulation of the PRKD1 promoter can provide valid information on the invasiveness of breast tumors, and therefore could serve as an early diagnostic marker. Moreover, targeted upregulation of PKD1 expression may be used as a therapeutic approach to reverse the invasive phenotype of breast cancer cells. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-05-24.

Abstract Background Trastuzumab (T) combined with chemotherapy improves survival of women with HER2-positive breast cancer. Dual therapy with T and other HER-2 targeted agents (lapatinib/pertuzumab) has demonstrated improved efficacy compared to T alone in advanced breast cancer, and is in clinical trials in early stage disease. We hypothesize that subgroups of patients with HER2-positive tumors and limited tumor burden (tumor size and no or few positive lymph nodes) have a favorable outcome and would not be candidates for dual therapy. This study will analyze the disease-free survival (DFS)and overall survival (OS) of patients with early stage breast cancer treated with chemotherapy and T in the seminal randomized studies (RCTs). Methods RCTs were identified by a Medline search from 2004-2013. Trial groups from five phase III RCTs agreed to provide data. TrialNumberEligibilityRegimenNSABP B312130T1-3; pN1, pN2a, or pN3a; M0ACx4 then Tx4 VSACx4 then THx4 then Hx40wkNCCTG N98313505T1-3; pN1-2; M0ACx4 then Tx12wk VS ACTx4 then Hx52wk VS ACx4 then Tx12wk then Hx40wkHERA5102T1-3; pN1-2; M0Any (neo)adjuvant regimen, then H q3wk x1yr VS H q3wk x 2yr VS observationFinHER232T1-4; N0-3; M0Vx3 or T*x3 then FECx3 VS Vx3 or T*x3 with Hx9wk then FECx3PACS043010(528 HER2+)T1-3; pN1-2; M0FE(100)Cx6 VSFE(100)Cx6 then Hx1yr VS T*E(75) x6 VS T*E(75) x6 then Hx1yrA, adriamycin; C, cyclophosphamide; T, paclitaxel; T*, docetaxel; H, trastuzumab; P, carboplatin; F, 5-fluorouracil; E, epirubicin; Treatment regimen also included 5 years of hormonal therapy for ER positive patients. The ER+/HER2+ and the ER-/HER2+ cohorts will be analyzed separately. Patients with tumors 3 cm or smaller (T1a, T1b, T1c and >2 cm- 3cm) and 0, 1, 2 and 3 positive lymph nodes will be included. Initially a log rank test will be used to determine if the survival results are different by study. If there is no difference across studies, Kaplan-Meier survival curves with confidence intervals will be estimated. If there is a difference between studies, individual Kaplan-Meier curves will be estimated and the mean of the curves will be estimated along with confidence intervals using the adjusted standard deviation. Estimates at 3, 5 and 8 years will be presented as well as estimates of the event rates within each subpopulation defined by tumor size, number of positive lymph nodes, and ER status. Survival endpoints of DFS, and OS as defined in the original studies will be analyzed. Results and Conclusion Data from the five trials will be analyzed and an abstract provided prior to the meeting. Subgroups of patients with a very favorable outcome when treated with adjuvant chemotherapy and T will be identified. Our survival estimates might serve as benchmarks for future trials evaluating therapy reduction. Our results will complement those of the Dana Farber single arm multicenter trial in patients with “low risk” HER2-positive disease (APT trial; NCT00542451), being submitted to SABCS 2013. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr S6-03.

Abstract Background: Imaging biomarkers of cellular division offer promise as non-invasive measures of tumor response. 3’-deoxy-3’[18F]-fluorothymidine ([18F]-FLT) positron emission tomography (PET) imaging generally correlates with pathology-based measurements of cancer proliferation, especially the Ki67 score. Though clinical studies have associated changes in [18F]-FLT uptake with therapeutic response, clinical studies validating its ability to assess cell proliferation are comparatively lacking. The goal of this study was to determine quantitative relationships between [18F]-FLT compared with molecular and cellular metrics of proliferation during treatment for locally advanced breast cancer (LABC). Methods: Baseline [18F]−FLT-PET scans were obtained prior to the initiation of chemotherapy for LABC from patients enrolled at several academic oncology study sites. MRI scans, and transmission CT scans were obtained. Core needle biopsies were obtained to determine Ki-67 indices using immuno-histochemistry and to assess an mRNA signature based measurement of proliferation. Prospectively specified quantitative relationships between PET, Ki67 immunohistochemistry and the mRNA signature were evaluated using image-matched tumor specimens. Correlations between volumetric MRI changes and pathologic responses were evaluated in a post-hoc exploratory analysis. Results: Motivated by the hypothesis that effective chemotherapies should decrease tumor cell proliferation, FLT-PET was compared with biomarkers of proliferation including Ki67 and the mRNA signature during neoadjuvant treatment for LABC. [18F]-FLT correlated both with the Ki67 labeling index (SUVmean r = 0.53) and with the proliferation signature (SUVmean r = 0.7), validating the principle of thymidine analogue imaging. However, variability in the [18F]-FLT PET and tumor cell proliferation measures likely contributed to correlations less than pre-specified target values considered appropriate for clinical use (r > 0.78). Moreover, none of the proliferation biomarkers predicted pathologic complete responses at the end of neoadjuvant therapy ∼16 weeks after the 3 week response scan. In contrast, an evaluation of change in tumor volume measured by MRI after 3 weeks of therapy confirmed its superior ability to predict pCR and tumor re-staging. Conclusion: With large numbers of cancer drugs entering therapeutic pipelines, early efficacy measures remain critical for drug development. The 3-4 month neoadjuvant treatment paradigm for LABC offers unique opportunities for drug evaluation. Functional imaging using [18F]-FLT has been advanced as an assessor of cellular proliferation, potentially offering a non-invasive approach to response evaluation. While [18F]-FLT generally correlated with proliferation, its lack of association with patient responses likely limit its clinical utility. On the other hand, the predictive value of MRI offers unique opportunities for future trial designs and confirms previous reports (1). 1. N. M. Hylton et al., Locally advanced breast cancer: MR imaging for prediction of response to neoadjuvant chemotherapy. Radiology 263, 663 (2012). Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-01-11.

Abstract Background A Phase III trial (Study 301; NCT00337103) in MBC comparing eribulin (E) with capecitabine (C) showed a trend for improved overall survival (OS) (hazard ratio [HR] 0.88; 95% CI 0.77, 1.00; P = 0.056) but not progression-free survival (PFS) (HR 1.08; 95% CI 0.93, 1.25; P = 0.30) with E. In order to investigate this apparent discordance, post-hoc analyses assessed the effect of PPT and events defining disease progression on OS. Methods Pts with locally advanced or MBC who had received an anthracycline and a taxane (≤2 prior chemotherapy regimens for advanced disease), were randomized to E (554) or C (548). Co-primary endpoints were OS and PFS. The impact of PPT on OS was assessed by analysis of exploratory PPT subgroups. Analyses of OS sensitivity censoring at time of PPT, and OS adjusted by PPT as a time-dependent covariate in a Cox regression model, were performed. The relationship between OS and progression events (appearance of a “new” lesion or metastasis [NM]; increase in size of pre-existing lesions [IPEL]; or other [death, clinical progression, or censored]) was investigated using Cox regression. Results PPT was received by 70% and 62% of E and C pts, respectively. For E pts, there were no significant OS differences by PPT (Table 1). Excluding 56 pts (22 E, 34 C) who received anti-HER2 therapy as PPT from the intent-to-treat OS analysis, OS was longer with E (HR 0.86; 95% CI 0.76, 0.99; nominal P = 0.03). OS sensitivity analysis censoring at time of PPT was consistent with the overall study results (HR 0.82; 95% CI 0.65, 1.03). Assessment of the overall effect of PPT, adjusting by PPT as a time-dependent covariate in a Cox regression model, showed that OS was longer with E (HR 0.85; 95% CI 0.75, 0.97; nominal P = 0.02). Progression due to NM or IPEL occurred in 271 and 147 of E pts, and 285 and 129 of C pts, respectively. Median OS was similar between arms in pts with IPEL and longer with E vs C in pts with NM (Table 2). Pts who progressed due to NM were at higher risk of death (HR 2.12; 95% CI 1.84, 2.43; nominal P<0.01). Conclusions Treatment with C or any other PPT after progression on E did not account for the trend in OS benefit with E observed in the primary analysis. Pts who progressed with NM had a worse prognosis than those with IPEL. The appearance of NM was highly correlated with OS, and the apparent discordance between PFS and OS seems to be related to these different progression events. Tab 1: OS by PPT after EPPTAll ptsC as 1stOther than C as 1stC at any timeOther than C at any timeNoneN554221169275115164Median OS, months (95% CI)15.9 (15.2, 17.6)18.3 (15.8, 20.9)19.9 (17.6, 24.0)19.6 (17.6, 21.5)18.0 (15.4, 22.7)7.4 (6.2, 9.1) Tab 2: OS by progression event Progression event NMIPELOther ECECECN271285147129136134Median OS, months (95% CI)15.5 (14.2, 17.5)12.9 (11.3, 14.5)17.4 (14.4, 19.7)17.4 (15.3, 20.9)16.7 (14.8, 24.2)15.5 (11.7, 18.3)HR (95% CI)0.81 (0.68, 0.97)1.13 (0.87, 1.46)0.78 (0.59, 1.03)Nominal P -value0.020.350.08Time to NM or death, months (95% CI)5.8 (5.2, 6.5)5.2 (4.3, 5.9)NANAHR (95% CI)0.90 (0.77, 1.05)NANANominal P-value0.17NANA Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-13-03.

Abstract Background: Hsp90 is a molecular chaperone protein required for the stabilization and activation of many proteins, referred to as Hsp90 ‘clients’, such as HER2, HIF1-a, EGFR, ER, PI3K, AKT, P53 and VEGFR. The drug candidate, ganetespib is a novel triazolone inhibitor of Hsp90, with over 700 patients treated to date. Ganetespib has shown activity in preclinical models of HER2+, ER+/PR+ and TNBC. Early clinical trials documented ganetespib single agent activity in heavily pretreated HER2+ and TNBC patients. Ganetespib has been well tolerated in clinical trials with a favorable safety profile. This efficacy-screening study is designed to provide further evidence of ganetespib activity and identify potentially predictive biomarkers in metastatic breast cancer (BC). Methods: The ENCHANT-1 Trial is an international, first-line 2-cohort Phase 2 study in BC patients: Cohort A, HER2 amplified (n = 35), and Cohort B, TNBC (n = 35). Patients who present with previously untreated metastatic disease are eligible for treatment with ganetespib at 150 mg/m2 twice weekly on 3 out of 4 wks, for a total of up to 12 wks. Primary endpoint: ORR assessed using RECIST1.1 criteria. Key secondary endpoints include metabolic response as assessed by PET/CT at wk 3 utilizing modified EORTC criteria. Disease progression (PD) at wk 3 by PET imaging indicates discontinuation of study therapy, and is performed to quickly offer patients with metabolic PD a standard of care treatment. The study is designed as Simon 2-stage requiring at least one OR in 15 patients for the respective cohort to expand to 35 patients. A Steering Committee is established to oversee the overall study and review the interim results. Results: The study was initiated in 23 centers globally. At the time of submission, a total of 17 patients had been enrolled; TNBC (n = 15) and HER2 (n = 2). Here we report the interim analysis in the TNBC cohort. The median age was 54 years (range 30 -77) with ECOG PS 0 (n = 7/15). Most patients (n = 9) presented with de novo metastatic disease. 5 patients were not evaluable for PET assessment (3 had not yet reached wk 3 and 2 withdrawn before wk 3 for clinical progression), and 9 patients were not evaluable for objective response at wk 6 (3 withdrawn before or at wk 3 for clinical progression and 6 had not yet reached wk 6 evaluation). In the 10 patients with evaluable PET imaging, 9 patients achieved metabolic (m) response (2 mPR, 4 mSD with dominant tumor shrinkage and 3 SD) and one patient with mPD. In the 6 patients evaluable for OR at wk 6, one patient achieved PR, 2 SD and 3 PD. Treatment with ganetespib was well tolerated; the most common AEs were mild or moderate diarrhea (8/15, 53%), fatigue (5/15, 33%), decreased appetite (4/15, 27%), insomnia (4/15, 27%), and nausea (4/15, 27%). Conclusion: Ganetespib single agent was generally well tolerated and showed anti-tumor activity TNBC patients as early as 3 weeks following treatment. PET seems to be a good tool to screen antitumor activity of new agents in early settings rather that in heavily pretreated patients. The TNBC cohort has met the protocol criteria for proceeding to stage 2. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-16-23.

Abstract Background: We have previously reported the results of surgical excision without irradiation for selected patients with DCIS in ECOG E5194, where the 5-year rates of local recurrence varied with age, grade, and lesion size (Hughes et al. J Clin Oncol 27:5319, 2009). New methods are needed to provide more accurate and reproducible assessment of recurrence risk. Methods: ECOG E5194 included 670 eligible patients with DCIS treated with surgical excision (≥ 3 mm negative margins) without irradiation, 228 of whom received tamoxifen. Patients had low or intermediate grade DCIS ≤ 2.5 cm, or high grade DCIS ≤ 1 cm. The Oncotype DX® assay was performed by quantitative RT-PCR using formalin fixed paraffin embedded tumor specimens from 327 patients (49% of the parent study). Recurrence Score® (RS) was calculated using the published algorithm. A new, prespecified DCIS Score™ was designed to predict recurrence using an optimized gene expression algorithm. The primary objective was to determine whether there was a significant association between the risk of an ipsilateral breast event (IBE) and the continuous DCIS Score in Cox models. 46 patients had an IBE (defined as ipsilateral local recurrence of DCIS [n=20] or invasive cancer [n=26]). Median follow-up was 8.8 years. Results: The 10-year IBE rates were 15.4% for low/intermediate grade DCIS and 15.1% for high-grade DCIS (as determined by central pathology review), and for invasive IBE, 5.6% and 9.8%, respectively. Comparison between local and expert grading showed substantial disagreement. Continuous DCIS Score was significantly associated with IBE (HR 2.34 per 50 units; 95% CI 1.15, 4.59; p=0.02) when adjusted for tamoxifen use (prespecified primary analysis) and with invasive IBE (HR 3.73; CI 1.34, 9.82; p=0.01). DCIS Score was significantly associated with outcome when evaluated by the prespecified risk groups (see Table). Similar results were observed with and without adjustment for tamoxifen use or for negative margin width. Features associated with IBE in multivariate models included menopausal status (HR 0.49; 95% CI 0.27, 0.90; p=0.02), tumor size (HR 1.52 per 5 mm; 95% CI 1.11, 2.01; p=0.01), and continuous DCIS Score (HR 2.41; 95% CI 1.15, 4.89; p=0.02). The standard RS, which is calculated using thresholding of many genes unlike the DCIS Score, was not associated with IBE or invasive IBE (p > 0.6). Conclusions: We have prospectively validated a multigene assay that quantifies recurrence risk and complements traditional clinical and pathologic factors in selected patients with DCIS treated with surgical excision without irradiation. The DCIS Score provides a new clinical tool for individualized selection of treatment for patients with DCIS. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr S4-6.

Abstract Bisphosphonates reduce the incidence of skeletal-related events (fractures, pain, hypercalcemia) in patients (pts) with bone metastases from breast cancer. By inhibiting osteoclast function and subsequent bone turnover they may inhibit the growth of bone (and other) metastases. Their role in preventing or delaying the development of bone (or other) metastases in pts with early breast cancer is uncertain. Three previous trials of oral clodronate have given mixed results. The largest trial (placebo-controlled) and a smaller open-label trial suggested that oral clodronate benefitted pts with improved bone metastases-free survival (BMFS) and overall survival (OS), but a third open-label study showed no benefit with an apparent detrimental effect on survival. Studies of IV zoledronate in open-label trials in early breast cancer have also shown mixed results: the AZURE trial in pts with node positive breast cancer showed no benefit in disease-free survival (DFS) or OS with a possible effect in pts aged over 60. The ABCSG-12 trial in GnRH (plus tamoxifen or anastrozole) treated women with early breast cancer showed a small DFS benefit for those receiving IV zoledronate but no BMFS or OS benefit. Methods: B-34 is a prospective, randomized, double-blind, phase III clinical trial in pts with stage 1, 2 or 3 breast cancer assessing oral clodronate 1600mg daily for 3 years compared to placebo given alone or in addition to adjuvant chemo- or hormone therapy. Stratification is by age (<50, +50), number of positive nodes (0, 1–3, 4+) and ER/PR status. The primary end-point is DFS. Secondary endpoints are the incidence of skeletal metastases, OS, relapse-free survival, incidence of non-skeletal metastases, and incidence of skeletal morbid events. Results: 3323 patients were accrued — 1662 in Group A and 1661 in Group B. As of March 31, 2011, 54 pts were declared ineligible: 23 in Group A and 31 in Group B. The average time on study is 101.3 months. Patient characteristics were evenly distributed throughout both groups. Approximately 75% of pts in each group had negative axillary lymph nodes and some 78% in each group were ER and/or PR positive. About 64% of pts were age 50 or over. Oral clodronate was generally tolerable, toxicities observed being mainly due to the concomitant systemic chemotherapy. One pt in Group A had a 1 mm area of osteonecrosis on the palatal taurus. Compliance, as expected with trials of oral medications, has been a problem. 1910 pts completed 3 years of therapy. Event rates were slower than anticipated. This final analysis assesses a total of 598 events in the two arms. Conclusions: This trial is the largest placebo-controlled study of an oral bisphosphonate in patients with early breast cancer and will provide further information on the role of bisphosphonates in breast cancer management. Supported for NSABP by NCI U10CA12027, −37377, 69651, 69974; and Bayer Schering Pharma Oy; for ECOG by U10CA021115; for NCCTG by U10CA25224; for SWOG by U10CA38926. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr S2-3.