Supplementary Figures 1-20 and Supplementary Tables 1-10 Legends

A coclinical trial framework reveals concordant patient–PDTX drug responses. A, Experimental framework (consisting of two trial designs) and associated analytical approach, with modeling metrics used to assess drug response. B and C, TV growth curves displaying linear mixed model fits of trial designs 1 (B) and 2 (C) over treatment duration. Treatment arm for each PDTX model corresponds to the clinical treatment of the matched patient. D and E, Analytical metrics derived from mathematical modeling (as in A). Change in growth rate (top) and estimated difference in the AUC (bottom) for trial design 1 (D) and growth rate under treatment (top) and predicted volume at treatment end (bottom) for trial design 2 (E). F, Box plots displaying growth rate under treatment (top) and predicted volume at treatment end (bottom) for trial design 2 between pCR and non-pCR models. Statistical significance is calculated using the Wilcoxon test.

The intertumor and intratumor heterogeneity of triple-negative breast cancers, which is reflected in diverse drug responses, interplays with tumor evolution. In this study, we developed a preclinical experimental and analytical framework using patient-derived tumor xenografts (PDTX) from patients with treatment-naïve triple-negative breast cancers to test their predictive value in personalized cancer treatment approaches. Patients and their matched PDTXs exhibited concordant drug responses to neoadjuvant therapy using two trial designs and dosing schedules. This platform enabled analysis of nongenetic mechanisms involved in relapse dynamics. Treatment resulted in permanent phenotypic changes, with functional and therapeutic consequences. High-throughput drug screening methods in ex vivo PDTX cells revealed patient-specific drug response changes dependent on first-line therapy. This was validated in vivo, as exemplified by a change in olaparib sensitivity in tumors previously treated with clinically relevant cycles of standard-of-care chemotherapy. In summary, PDTXs provide a robust tool to test patient drug responses and therapeutic regimens and to model evolutionary trajectories. However, high intermodel variability and permanent nongenomic transcriptional changes constrain their use for personalized cancer therapy. This work highlights important considerations associated with preclinical drug response modeling and potential uses of the platform to identify efficacious and preferential sequential therapeutic regimens. Significance: Patient-derived tumor xenografts from treatment-naïve breast cancer samples can predict patient drug responses and model treatment-induced phenotypic and functional evolution, making them valuable preclinical tools.

Poly (ADP-ribose) polymerase inhibitors (PARPi) exploit DNA repair deficiency in germline BRCA1 and BRCA2 pathogenic variant (gBRCAm) cancers. Haematological toxicity limits chemotherapy-PARPi treatment combinations. In preclinical models we identified a schedule combining olaparib and carboplatin that avoids enhanced toxicity but maintains anti-tumour activity. We investigated this schedule in a neoadjuvant, phase II-III, randomised controlled trial for gBRCAm breast cancers (ClinicalTrials.gov ID:NCT03150576; PARTNER). The research arm included carboplatin (Area Under the Curve 5, 3-weekly); paclitaxel (80 mg/m2, weekly) day 1, plus olaparib (150 mg twice daily) day 3-14 (4 cycles), followed by anthracycline-containing chemotherapy (3 cycles); control arm gave chemotherapy alone. The primary endpoint, pathological complete response rate, showed no statistical difference between research 64.1% (25/39); control 69.8% (30/43) (p = 0.59). However, estimated survival outcomes at 36-months demonstrated improved event-free survival: research 96.4%, control 80.1% (p = 0.04); overall survival: research 100%, control 88.2% (p = 0.04) and breast cancer specific survival: research 100%, control 88.2% (p = 0.04). There were no statistical differences in relapse-free survival and distant disease-free survival, both were: research 96.4%, control 87.9% (p = 0.20). Similarly, local recurrence-free survival and time to second cancer were both: research 96.4%, control 87.8% (p = 0.20). The PARTNER trial identified a safe, tolerable schedule combining neoadjuvant chemotherapy with olaparib. This combination demonstrated schedule-dependent overall survival benefit in early-stage gBRCAm breast cancer. This result needs confirmation in larger trials.

Whole genome sequencing (WGS) provides comprehensive, individualised cancer genomic information. However, routine tumour biopsies are formalin-fixed and paraffin-embedded (FFPE), damaging DNA, historically limiting their use in WGS. Here we analyse FFPE cancer WGS datasets from England's 100,000 Genomes Project, comparing 578 FFPE samples with 11,014 fresh frozen (FF) samples across multiple tumour types. We use an approach that characterises rather than discards artefacts. We identify three artefactual signatures, including one known (SBS57) and two previously uncharacterised (SBS FFPE, ID FFPE), and develop an "FFPEImpact" score that quantifies sample artefacts. Despite inferior sequencing quality, FFPE-derived data identifies clinically-actionable variants, mutational signatures and permits algorithmic stratification. Matched FF/FFPE validation cohorts shows good concordance while acknowledging SBS, ID and copy-number artefacts. While FF-derived WGS data remains the gold standard, FFPE-samples can be used for WGS if required, using analytical advancements developed here, potentially democratising whole cancer genomics to many. Formalin fixation is commonly used in tissue storage; however, this process has traditionally limited downstream whole genome sequencing usage. Here, the authors identify artefactual signatures in FFPE-derived sequencing data and demonstrate the preservation of clinical utility, thus enabling FFPE whole genome sequencing when required.

PARTNER is a prospective, phase II-III, randomized controlled clinical trial that recruited patients with triple-negative breast cancer1,2, who were germline BRCA1 and BRCA2 wild type3. Here we report the results of the trial. Patients (n = 559) were randomized on a 1:1 basis to receive neoadjuvant carboplatin-paclitaxel with or without 150 mg olaparib twice daily, on days 3 to 14, of each of four cycles (gap schedule olaparib, research arm) followed by three cycles of anthracycline-based chemotherapy before surgery. The primary end point was pathologic complete response (pCR)4, and secondary end points included event-free survival (EFS) and overall survival (OS)5. pCR was achieved in 51% of patients in the research arm and 52% in the control arm (P = 0.753). Estimated EFS at 36 months in the research and control arms was 80% and 79% (log-rank P > 0.9), respectively; OS was 90% and 87.2% (log-rank P = 0.8), respectively. In patients with pCR, estimated EFS at 36 months was 90%, and in those with non-pCR it was 70% (log-rank P < 0.001), and OS was 96% and 83% (log-rank P < 0.001), respectively. Neoadjuvant olaparib did not improve pCR rates, EFS or OS when added to carboplatin-paclitaxel and anthracycline-based chemotherapy in patients with triple-negative breast cancer who were germline BRCA1 and BRCA2 wild type. ClinicalTrials.gov ID: NCT03150576 .

Abstract Background: TNBCs in patients (pts) who are germline BRCA wild type (gBRCAwt) may show homologous recombination deficiency and genomic instability, resulting in a BRCA-like phenotype. The PARTNER Trial tested olaparib in combination with neoadjuvant carboplatin and paclitaxel in pts with TNBC (gBRCAwt). Methods: Pts with TNBC diagnosed locally were confirmed centrally with immunohistochemistry for ER, PR, HER2 and EGFR, CK5/6 and AR to define basal-like TNBC, before entry to the PARTNER trial. Pts were gBRCAwt. Tumours were assessed for tumour infiltrating lymphocytes (TILs). Pts were randomised 1:1 to research (R) and control arms (C). Pts received neoadjuvant carboplatin AUC 5, day(d) 1, with paclitaxel 80mg/m2 d1, 8, 15, every (q) 3 weeks (w), x 4 cycles(cy), +/- olaparib 150mg bd, po, d3-14 q 3w. Then all pts had 3cy of anthracycline chemotherapy before surgery. Primary endpoint was pathological complete response (pCR), and secondary endpoints included event-free survival (EFS), and overall survival (OS). A total of 454 patients were needed to attest 90% power with 5% significance assuming pCR rate of 50% in C and 65% in R. Results: From Sept 2016 to Dec 2021, 559 pts with TNBC (gBRCAwt) were randomised at 29 UK centres. Data cut-off was 30/11/23 with median (med) follow-up of 38 months (m). There were 276 R and 264 C pts in the intention-to-treat population. Pt and tumour characteristics were balanced between the arms: med pt age 49 years; 95% ECOG 0; 36% previous oophorectomy or post-menopausal; 95% tumour size ≤50mm; TILS score ≥60% in 22%. In R, 88% received at least 80% of the planned olaparib dose. More than 90% of patients in both R and C received at least 80% of the planned carboplatin (R 96% and C 94%) and paclitaxel (R 100% and C 99%) doses.Of 543 pts, 141 (51.1%) in R and 140 (52.4%) in C had a pCR with a difference of -1.3% (95% CI -9.7% to 7.0%, p-value=0.753). Percentage of pts with pCR increased with increasing TILs; pCR rate was 32% with TILs 0-10%, increasing to 67% with TILs 90-100%. Estimated EFS at 36 months (m) was 80% in R and 79% in C (log-rank p>0.9); estimated OS at 36m was 90% in R and 87.2% in C (log-rank p=0.8). Estimated 36m EFS rate was 90.4% (95% CI, 86.4 to 94.5) in pts with pCR and 70% (95% CI, 64.2 to 76.2) in pts with non-pCR (HR=0.3, 95% CI 0.2 to 0.4; p < 0.001). Estimated 36m OS was 95.7% (95% CI, 93.0 to 98.5) in pts with pCR, and 83% (95% CI, 78 to 88.2) in pts with non-pCR (HR=0.2, 95% CI 0.1 to 0.3; p < 0.001). More events and deaths were observed in non-pCR pts compared to pCR pts regardless of the treatment received. Conclusions: Neo-adjuvant olaparib in the dose and schedule tested, in addition to carboplatin/taxol and anthracycline chemotherapy in basal-like TNBC in gBRCAwt patients, did not improve pCR rates, EFS or OS. Pts who achieved a pCR had significantly better EFS and OS than those with non-pCR. These results are in marked contrast to the significant benefit of olaparib in those with gBRCA mutations reported in parallel. Citation Format: Jean E. Abraham, Karen Pinilla, Louise Grybowicz, Alimu Dayimu, Nikolaos Demiris, Caron Harvey, Lynsey M. Drewett, Rebecca Lucey, Alexander Fulton, Anne N. Roberts, Joanna R. Worley, Anita Chhabra, Wendi Qian, Richard M. Hardy, Stephen Chan, Tamas Hickish, Devashish Tripathi, Ramachandran Venkitaraman, Mojca Persic, Shahzeena Aslam, Daniel Glassman, Sanjay Raj, Annabel Borley, Jeremy P. Braybrooke, Stephanie Sutherland, Emma Staples, Lucy C. Scott, Mark Davies, Cheryl A. Palmer, Margaret Moody, Mark J. Churn, Jacqueline C. Newby, Mukesh B. Mukesh, Amitabha Chakrabarti, Rebecca R. Roylance, Philip C. Schouten, Nicola Levitt, Karen McAdam, Anne C. Armstrong, Ellen R. Copson, Emma McMurtry, Marc Tischkowitz, Elena Provenzano, Helena Earl, PARTNER Trial Group. PARTNER Trial: Neoadjuvant olaparib in triple negative breast cancer (TNBC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT012.

ABSTRACT Triple negative breast cancers (TNBC) exhibit inter- and intra-tumour heterogeneity, which is reflected in diverse drug responses and interplays with tumour evolution. Here, we use TNBC patient-derived tumour xenografts (PDTX) as a platform for co-clinical trials to test their predictive value and explore the molecular features of drug response and resistance. Patients and their matched PDTX exhibited mirrored drug responses to neoadjuvant therapy in a clinical trial. In parallel, additional clinically-relevant treatments were tested in PDTXs in vivo to identify alternative effective therapies for each PDTX model. This framework establishes the foundation for anticipatory personalised therapies for those patients with resistant or relapsed tumours. The PDTXs were further explored to model PDTX- and treatment-specific behaviours. The dynamics of drug response were characterised at single-cell resolution revealing a novel mechanism of response to olaparib. Upon olaparib treatment PDTXs showed phenotypic plasticity, including transient activation of the immediate-early response and irreversible sequential phenotypic switches: from epithelial to epithelial-mesenchymal-hybrid states, and then to mesenchymal states. This molecular mechanism was exploited ex vivo by combining olaparib and salinomycin (an inhibitor of mesenchymal-transduced cells) to reveal synergistic effects. In summary, TNBC PDTXs have the potential to help design individualised treatment strategies derived from model-specific evolutionary insights.

TPS619 Background: Triple negative breast cancers (TNBCs) are a biologically diverse and aggressive subgroup lacking targeted therapy. TNBC and germline BRCA (gBRCA) breast cancer share certain phenotypic and molecular similarities, with gBRCA mutations seen in 10% to 20% of TNBC patients. Homologous recombination-deficient tumors, especially those caused by germline or somatic BRCA mutations, are thought to be particularly sensitive to PARP inhibitors. Methods: This is a 3-stage open-label randomized phase II/III trial of neoadjuvant paclitaxel and carboplatin +/- olaparib, followed by clinicians' choice of anthracycline regimen. The aim is to establish whether the addition of olaparib to neoadjuvant platinum-based chemotherapy in the treatment of basal TNBC and/or gBRCA breast cancer is safe and increases efficacy. In stages 1 and 2, all patients receive 4 cycles of 3-weekly carboplatin AUC5/weekly paclitaxel 80mg/m2. They are randomly assigned 1:1:1 to a control arm, or to one of two research arms. These research arms include different treatment schedules of olaparib 150 mg BD for 12 days. In stage 3, patients are randomly assigned 1:1 to either the control or research arm chosen following stage 2. The primary endpoints are: Stage 1: Safety; Stage 2: Schedule selection based on pCR rate and olaparib completion rate using a “pick-the-winner” design. Stage 3: pCR rate. Key eligibility criteria are age 16-70; histologically confirmed invasive breast cancer; ER-negative, HER2-negative with TNBC basal phenotype or gBRCA positive, HER2-negative irrespective of hormone status; stage T1-4 N0-2; performance status 0-1; treatment within 6 weeks of diagnostic biopsy; biomarker scores: TILs, CK 5/6, EGFR +/- AR. The recruitment of TNBC non-gBRCA and gBRCA patients is independent. Enrichment design is applied with an overall significance level 0.05(α) and 80% power. A minimum of 780 patients will be included to detect an absolute improvement of 15% (all patients) and 20% (gBRCA patients) by combining olaparib with platinum-based chemotherapy. This trial includes an optional pathway called PARTNERING for patients with residual disease after six chemotherapy cycles. This aims to establish if adding new agents (ATR inhibitor and PD-L1 inhibitor) improves treatment response. Each cohort will consist of 15 patients. Since May 2016, 756 patients from 30 sites have been enrolled. An IDSMC review following stages 1 and 2 identified no safety concerns and Research Arm 2 was selected (olaparib administration on days 3-14). Stage 3 phase I (recruitment of non-gBRCA and gBRCA patients) completed December 2021. Stage 3 phase II (recruitment of gBRCA patients) remains open to patients in the U.K. and internationally. 5 patients have enrolled in PARTNERING. Follow-up duration is 10 years. Clinical trial information: NCT03150576.

Background: Triple negative breast cancers (TNBCs) are an aggressive and diverse subgroup with no specific targeted therapies currently available. Basal TNBCs show some phenotypic and molecular similarities with germline BRCA mutated BC (gBRCA). In gBRCA patients, and potentially other homologous recombination deficiencies, these already compromised pathways may allow PARP inhibitors (olaparib) to work more effectively. PARTNER was designed to establish if the addition of olaparib to neoadjuvant platinum-based chemotherapy for gBRCA and/or basal TNBC is safe and improves efficacy (pathological complete response (pCR)). This is the first time a clinical trial provides safety data of the combination of olaparib with platinum and taxane chemotherapy in an early breast cancer setting. Methods: PARTNER is a 3-stage open label randomised Phase II/III trial of neoadjuvant Carboplatin AUC5 with weekly Paclitaxel 80mg/m2 (CP) +/- olaparib (O) 150mgBD for 12 days x 4 cycles, followed by clinicians9 choice of anthracycline regimen x 3 cycles. Basal-TNBC and/or gBRCA patients are eligible for inclusion. Primary endpoints are defined by stage: Stage 1 - Safety, Stage2 - Schedule selection, and Stage 3 - Efficacy (pCR rate). The trial is now powered for efficacy analysis in the BRCA and non-BRCA population independently. Stage 1 and 2 randomization was(1:1:1) to CP: CP + O from day (D) -2: or CP + O from D 3. G-CSF was mandatory during the first 4 cycles of treatment. We present a pooled-safety analysis from Stage 1 and 2 of the two research arms only. Recruitment continues into Stage 3. Results: Between June 2016 and April 2018, 159 patients were recruited among the three arms. Overall, median age was 48.2 [range 22.3- 70.9]; 12% had Tumours >5cm, 34% had Axillary involvement; 17% were gBRCA. Adverse events (AE) that were reported as common (in at least 10% of patients) were Anaemia 23%, Neutropenia 18% and Infection 10%. Fatigue and Diarrhoea were next most prevalent with 9% and 6% respectively. The most common AE Grade >=3 were haematological events. These include Neutropenia 19%, Anaemia 15%, and Thrombocytopenia 5%. Febrile Neutropenia and Haemorrhage were reported in only 2% and 1% of cases. Grade 3 Non- haematological events were Fatigue 7%, Hypertension 3%, Headache 3% and Diarrhoea 2%. Grade 3 Sensory neuropathy was present in 2% of patients. No grade 4 sensory or motor neuropathy events were described. Serious adverse reactions related to investigational regimen were reported in 17% of patients and include fever and infection with 8 and 4 events respectively. No toxicity related deaths were reported. As per July 8th 2019, 373 patients have been recruited from which 58 were gBRCA. Conclusions: Combinations of olaparib with neoadjuvant CP chemotherapy showed an acceptable and manageable toxicity profile. Although haematological events were the most common, they did not exceed historical frequencies reported for standard chemotherapy regimens. Final safety analysis will be performed once recruitment is complete and will include detailed long-term neuropathy data. Citation Format: Karen Pinilla Alba, Emma McMurtry, Anne-Laure Vallier, Louise Grybowicz, Ellen Copson, Anne Armstrong, Rebecca Roylance, Wendi Qian, Nikolaos Demiris, Stanly Thomas, Caron Harvey, Luke Hughes-Davies, Karen McAdam, Paula del Rosario, Bryony Harrop, Elena Provenzano, Marc Tischkowitz, Helena M Earl, Jean E Abraham. Preliminary safety data from stage 1 and 2 of the phase II/III PARTNER trial: Addition of olaparib to platinum-based neoadjuvant chemotherapy in triple negative and/or germline BRCA mutated breast cancer patients [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-10-05.

The ARTemis Trial tested standard neoadjuvant chemotherapy±bevacizumab in the treatment of HER2-negative early breast cancer. We compare data from central pathology review with report review and also the reporting behavior of the two central pathologists. Eight hundred women with HER2-negative early invasive breast cancer were recruited. Response to chemotherapy was assessed from local pathology reports for pathological complete response in breast and axillary lymph nodes. Sections from the original core biopsy and surgical excision were centrally reviewed by one of two trial pathologists blinded to the local pathology reports. Pathologists recorded response to chemotherapy descriptively and also calculated residual cancer burden. 10% of cases were double-reported to compare the central pathologists’ reporting behavior. Full sample retrieval was obtained for 681 of the 781 patients (87%) who underwent surgery within the trial and were evaluable for pathological complete response. Four hundred and eighty-three (71%) were assessed by JSJT, and 198 (29%) were assessed by EP. Residual cancer burden calculations were possible in 587/681 (86%) of the centrally reviewed patients, as 94/681 (14%) had positive sentinel nodes removed before neoadjuvant chemotherapy invalidating residual cancer burden scoring. Good concordance was found between the two pathologists for residual cancer burden classes within the 65-patient quality assurance exercise (kappa 0.63 (95% CI: 0.57–0.69)). Similar results were obtained for the between-treatment arm comparison both from the report review and the central pathology review. For pathological complete response, report review was as good as central pathology review but for minimal residual disease, report review overestimated the extent of residual disease. In the ARTemis Trial central pathology review added little in the determination of pathological complete response but had a role in evaluating low levels of residual disease. Calculation of residual cancer burden was a simple and reproducible method of quantifying response to neoadjuvant chemotherapy as demonstrated by performance comparison of the two pathologists.

1014 Background: ARTemis compared the addition of Bev to neoadjuvant D-FEC in HER2 negative breast cancer. Improved pathological complete response (pCR) with Bev has been reported previously. Methods: We enrolled women ≥ 18 yrs with radiological tumour size > 20mm, ± axillary involvement, at 66 centres in the UK. Patients (pts) were randomly assigned to 3 cycles of D (100 mg/m² every [q] 21 days [d]) followed by 3 cycles of F (500mg/m2), E (100mg/m2) and C (500 mg/m²) q 21d (D-FEC), ± 4 cycles Bev (15mg/kg) (Bev+D-FEC). We present the DFS and OS results, analysed by intention-to-treat. pCR is defined by report review; analysis by central pathology review will be available at the time of presentation. Results: Between May'09 and Jan'13, we randomised 800 pts; 401 to D-FEC and 399 to Bev+D-FEC. Median follow-up was 3.4 yrs (IQR 2.5–4.4). 131 deaths and 183 DFS events have occurred. Both OS and DFS were similar across treatments (3-yr OS: Bev+D-FEC 85%, D-FEC 87%; hazard ratio (HR) 0.80 (95%CI 0.57-1.12) p = 0.19. 3-yr DFS: Bev+D-FEC 77%, D-FEC 80%; HR 0.86 (95%CI 0.64-1.14) p = 0.29). pCR was associated with improved OS in D-FEC pts (3-yr OS: pCR 96%, non-pCR 84%; log-rank p = 0.01) but not with Bev+D-FEC (3-yr OS: pCR 87%, non-pCR 83%; log-rank p = 0.71). Similarly pCR predicted for improved DFS with D-FEC (3-yr DFS: pCR 97%, non-pCR 76%; log-rank p = 0.0006), but not with Bev+D-FEC (3-yr DFS: pCR 84%, non-pCR 74%; log-rank p = 0.19). There was borderline heterogeneity in the effect of the addition of Bev between pCR and non-pCR groups in terms of OS (p = 0.07), and significant heterogeneity in terms of DFS (p = 0.02). Conclusions: Although Bev+D-FEC produced significantly higher pCR rates when added to chemotherapy in the ARTemis trial, OS and DFS were not improved. Moreover pCR achieved by Bev+D-FEC does not appear to be associated with the improved OS and DFS which is seen with pCR achieved by D-FEC. This data suggests that micro-metastatic breast cancer may be angiogenesis-independent and hence not altered by neoadjuvant Bev treatment. Clinical trial information: ISRCTN 68502941.

Abstract Background: Bevacizumab (bev) has been used with neo-adjuvant chemotherapy (NACT) in breast cancer trials. Geparquinto reported benefit for bev in triple negative (neg) patients (pts) (pathological complete response (pCR) 36.4% vs 27.8% p=0.02), as did CALGB 40603 (pCR 52% vs 44%, p=0.057), although NSABP-B40 showed benefit in ER positive (pos) pts (pCR 23.3% vs 15.2%, p=0.008). Methods: ARTemis is a randomised phase 3 trial adding bev to NACT (docetaxel (D)-FEC). Pts with HER2-neg invasive breast cancer were eligible. Stratification was by age, ER status (neg:weak pos:strong pos), tumour size (T2:T3/4), clinical involvement of axillary nodes and inflammatory/locally advanced disease. Pts were randomised (1:1) to bev+D-FEC or D-FEC. The primary endpoint was pCR, defined as no residual invasive cancer in the breast or axillary lymph nodes after NACT. 800 pts were required to detect 10% differences in pCR rates; 85% power, 5% alpha level. Results: 800 pts were randomised from 66 UK centres (May 2009 to Jan 2013). 68% were <50 years old, 19% had inflammatory and/or locally advanced disease, 79% of tumours <50mm, 52% clinical node pos and 33% ER-neg. A 2-reader independent review of pathology reports determined whether pCR had been achieved or, at least, minimal residual disease (MRD) status. Significantly more pts on bev+D-FEC had a pCR (22% vs 17%; adjusted p=0.03) (see table). pCR rates differed significantly across ER groups (neg 38%, weak pos 39%, strong pos 7%; p<0.0001). Treatment effect of bev remained significant after adjustment for ER (p=0.03). Similarly significantly more pts on bev+D-FEC had a pCR or MRD (36% vs 29%; adjusted p=0.035). Rates differed significantly across ER groups (neg 51%, weak pos 58%, strong pos 18%; p<0.0001). Treatment effect of bev remained significant after adjustment for ER (p=0.03). D→FECBev+D→FEC % (95%CI)% (95%CI)p *$pCR in all breast tumours AND absence of disease in ax LNs in all breast tumours(n=66/393)(n=87/388) 17% (13-21%)22% (18-27%)0.03 ER neg (Allred 0-2) (n=253)32% (24-41)44% (36-54) ER weak pos (Allred 3-5) (n=67)26% (13-44)52% (34-69) ER strong pos (Allred 6-8) (n=461)7% (4-11)6% (3-10) pCR or MRD in all breast tumours(n=114/394)(n=138/388) 29% (25-34%)36% (31-41%)0.035 ER neg (Allred 0-2) (n=254)45% (36-54)56% (47-65) ER weak pos (Allred 3-5) (n=67)44% (27-62)73% (54-87) ER strong pos (Allred 6-8) (n=461)18% (13-23)19% (14-24) * Adjusted for stratification variables. $ Primary endpoint for the ARTemis trial Conclusions: ARTemis showed a significant improvement in both pCR and MRD rates with the addition of bev to D-FEC. ER-neg and ER-weak pos / HER2-neg breast cancer pts appeared to benefit most from bev, whilst pCR and MRD rates in ER-strong pos pts were lower and did not appear to benefit from bev. Our results are similar to those reported in Geparquinto and CALGB 40603. Citation Format: Helena M Earl, Louise Hiller, Janet A Dunn, Clare Blenkinsop, Louise Grybowicz, Anne-Laure Vallier, Jean Abraham, Jeremy Thomas, Elena Provenzano, Luke Hughes-Davies, Karen McAdam, Stephen Chan, Rizvana Ahmad, Tamas Hickish, Stephen Houston, Daniel Rea, John Bartlett, Carlos Caldas, David Cameron, Larry Hayward. ARTemis: A randomised trial of bevacizumab with neo-adjuvant chemotherapy for patients with HER2-negative early 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 PD2-3.

BACKGROUND:The ARTemis trial was developed to assess the efficacy and safety of adding bevacizumab to standard neoadjuvant chemotherapy in HER2-negative early breast cancer. METHODS:In this randomised, open-label, phase 3 trial, we enrolled women (≥18 years) with newly diagnosed HER2-negative early invasive breast cancer (radiological tumour size >20 mm, with or without axillary involvement), at 66 centres in the UK. Patients were randomly assigned via a central computerised minimisation procedure to three cycles of docetaxel (100 mg/m(2) once every 21 days) followed by three cycles of fluorouracil (500 mg/m(2)), epirubicin (100 mg/m(2)), and cyclophosphamide (500 mg/m(2)) once every 21 days (D-FEC), without or with four cycles of bevacizumab (15 mg/kg) (Bev+D-FEC). The primary endpoint was pathological complete response, defined as the absence of invasive disease in the breast and axillary lymph nodes, analysed by intention to treat. The trial has completed and follow-up is ongoing. This trial is registered with EudraCT (2008-002322-11), ISRCTN (68502941), and ClinicalTrials.gov (NCT01093235). FINDINGS:Between May 7, 2009, and Jan 9, 2013, we randomly allocated 800 participants to D-FEC (n=401) and Bev+D-FEC (n=399). 781 patients were available for the primary endpoint analysis. Significantly more patients in the bevacizumab group achieved a pathological complete response compared with those treated with chemotherapy alone: 87 (22%, 95% CI 18-27) of 388 patients in the Bev+D-FEC group compared with 66 (17%, 13-21) of 393 patients in the D-FEC group (p=0·03). Grade 3 and 4 toxicities were reported at expected levels in both groups, although more patients had grade 4 neutropenia in the Bev+D-FEC group than in the D-FEC group (85 [22%] vs 68 [17%]). INTERPRETATION:Addition of four cycles of bevacizumab to D-FEC in HER2-negative early breast cancer significantly improved pathological complete response. However, whether the improvement in pathological complete response will lead to improved disease-free and overall survival outcomes is unknown and will be reported after longer follow-up. Meta-analysis of available neoadjuvant trials is likely to be the only way to define subgroups of early breast cancer that would have clinically significant long-term benefit from bevacizumab treatment. FUNDING:Cancer Research UK, Roche, Sanofi-Aventis.