Evaluation of RAD1901, a novel investigational, selective estrogen receptor degrader (SERD), for the treatment of ER-positive (ER+) advanced breast cancer.

2017 ◽  
Vol 35 (15_suppl) ◽  
pp. 1014-1014 ◽  
Author(s):  
Aditya Bardia ◽  
Peter Kabos ◽  
Richard Elledge ◽  
Dannie Wang ◽  
Jinshan Shen ◽  
...  

1014 Background: The treatment of advanced ER+ breast cancer remains a clinical challenge with the majority of patients eventually progressing due to resistance to endocrine therapy. RAD1901 is a novel, nonsteroidal, oral SERD that has demonstrated dose dependent degradation of ER, and ER regulated genes in preclinical studies. In multiple in vivo patient derived xenograft models of breast cancer, including those harboring ESR1 mutations, RAD1901 demonstrated significant antitumor activity. Methods: In a phase-1 Study RAD1901-005 (ClinicalTrials.gov ID: NCT02338349), patients with advanced ER+ breast cancer were enrolled in dose escalation cohorts, followed by a safety expansion cohort. Key inclusion criteria include postmenopausal women aged 18 years or older, with advanced ER+, HER2- breast cancer, who have received ≤ 2 prior chemotherapy regimens in the metastatic setting and > 6 months of prior endocrine therapy. ESR1 mutation status was determined from circulating tumor DNA (ctDNA) samples. Clinical outcomes were evaluated based on RECIST v1.1 criteria. Results: As of January 25, 2017, total of 39 patients were enrolled at the 400 mg qd dose. Patients were heavily pre-treated (median lines of prior therapy = 3), with 38% and 41% having previously received fulvestrant and palbociclib/CDK4/6 inhibitor, respectively. RAD1901 was generally well-tolerated, with the most common adverse events being low grade nausea (Grade 3/4 = 0%) and dyspepsia (Grade 3/4 = 0%). ESR1 mutations, including D538G, Y537S/N/C, L536H/P/R, S436P and E380Q, were detected at baseline in 44% of patients and dynamic changes in the allele frequency of ESR1 mutations were observed in response to treatment. Confirmed partial responses were observed in patients with ESR1 mutations, and those who had previously received fulvestrant and palbociclib. Conclusions: RAD1901 has demonstrated evidence of single agent activity, with confirmed partial responses in heavily pre-treated patients with advanced ER+ breast cancer, including those with ESR1 mutations, warranting additional clinical development. Clinical trial information: NCT02338349.

2021 ◽  
Vol 39 (15_suppl) ◽  
pp. 1018-1018
Author(s):  
Erika P. Hamilton ◽  
Judy S. Wang ◽  
Timothy J. Pluard ◽  
Stephen R. D. Johnston ◽  
Aki Morikawa ◽  
...  

1018 Background: H3B-6545, a selective, small molecule covalent antagonist of ERα demonstrated preclinical and preliminary clinical activity against ER+ breast cancer (Hamilton EP, SABCS, 2020). This study evaluated the activity and tolerability of H3B-6545 in patients (pts) with metastatic ER+, HER2-, breast cancer refractory to endocrine therapy. Methods: Patients received H3B-6545 once daily at the recommended phase II dose of 450 mg. The primary objective of the phase II is to estimate the objective response rate (ORR), progression-free survival (PFS), clinical benefit rate (CBR) and secondary objectives include safety. Results: 83 pts were treated with 450 mg in the phase II part of the trial. Additionally, 11 pts were treated with 450 mg in the phase I part of the trial and are included in this analysis. Median age was 62 years (range: 38 to 87 years), 81% had liver and/or lung metastases, and the median number of prior therapies for metastatic disease was 3 (range: 1 to 8). Prior CDK4/6 inhibitors, aromatase inhibitors, fulvestrant, and chemotherapy were received by 85%, 80%, 72%, and 50% of the pts, respectively. 58 pts (62%) had detectable ESR1 mutations in liquid biopsies, including 10 (11%) and 19 pts (20%) who had clonal Y537S and clonal D538G mutation, respectively. As of January 29, 2021, grade (gr) 2 or higher adverse events (AE) reported in ≥10% were anemia (19%), fatigue (16%), nausea (17%), and diarrhea (12%). Laboratory gr 2 or higher abnormalities reported in ≥10% pts were creatinine clearance decrease (38%), hemoglobin decrease (37%), bilirubin increase (12%), ALT increase (14%), AST increase (13%), and creatinine increase (11%). AE of gr 1 sinus bradycardia (asymptomatic) was reported in 34% and gr 2 (symptomatic, no intervention needed) was reported in 5%. Gr 2 and 3 QTcF prolongation were reported in 2 and 3 pts, respectively. There were no treatment-related deaths. Efficacy estimates are presented in the table below. Responses were observed in heavily pretreated pts, pts with visceral metastases and in pts who received prior fulvestrant, CDK4/6 inhibitor, and/or chemotherapy in the metastatic setting. Conclusions: H3B-6545 has a manageable safety profile and demonstrated single-agent anti-tumor activity in heavily pretreated ER+, HER2- mBC patients. Clinical activity was observed in pts with ESR1 mutations. Clinical trial information: NCT03250676 .[Table: see text]


2017 ◽  
Vol 9 (7) ◽  
pp. 465-479 ◽  
Author(s):  
Katalin Boér

Breast cancer is a classical hormone-dependent tumour; therefore, endocrine therapy is the mainstay of treatment for hormone receptor-positive, human epidermal growth factor 2-negative advanced breast cancer. Until recently, classical endocrine agents such as tamoxifen, steroidal and nonsteroidal aromatase inhibitors and fulvestrant have been widely used in postmenopausal patients to treat locally advanced or metastatic disease. However, for patients with this subtype of breast cancer, the landscape of endocrine therapy is rapidly changing. Therapies targeting oestrogen modulation have evolved in recent years following the introduction of targeted agents, mTOR and CDK 4/6 inhibitors that are administered in combination with hormone therapy. As a result, options for endocrine therapy have expanded in recent years, and a variety of single-agent or combinations of targeted drugs and endocrine therapies are accepted. Fulvestrant is a selective oestrogen receptor downregulator (SERD) which was introduced to clinical practice in 2002, initially with the indication to treat postmenopausal women with hormone-receptor-positive advanced breast cancer as second-line therapy postdisease progression after aromatase inhibitors or tamoxifen. Additionally, fulvestrant has also been shown to be active in patients previously untreated with endocrine therapy, either both in the neoadjuvant and the metastatic setting, alone or in combination with other targeted therapies. Currently, the standard dose is 500 mg, which is administered with a loading dose. Fulvestrant received a new FDA indication in December 2016, in combination with palbociclib, both in pre/peri/postmenopausal women with breast cancer progressing after endocrine therapy. This manuscript aims to give an overview of new efficacy data and the current role of fulvestrant in the systemic therapy of hormone-receptor-positive advanced breast cancer, in the context of other available therapeutic modalities.


2013 ◽  
Vol 31 (15_suppl) ◽  
pp. e12018-e12018
Author(s):  
Pinar Gursoy ◽  
Zeki Gokhan Surmeli ◽  
Burcu Cakar ◽  
Cagatay Arslan ◽  
Baha Zengel ◽  
...  

e12018 Background: Addition of capecitabine to docetaxel improves survival outcomes compared with single agent docetaxel in metastatic breast cancer (MBC). In this study we analyzed efficacy of maintenance therapy with single agent capecitabine after six cycles of docetaxel/capecitabine chemotherapy in MBC patients. Methods: Patients with metastatic HER2 negative breast cancer were included. Six cycles of docetaxel (75mg/m2 q3wk) / capecitabine (1650mg/m2/day on days 1 to 14) followed by capecitabine (2000 mg/m2/day on days 1 to 14) were administered. Demographic features, progression free (PFS) and overall survival (OS) and response to treatment were recorded. Results: Fifty-four patients were included. Thirty-five patients (65%) were postmenopausal, and 40 (74%) were ER/PR positive. Median age was 53 (range 28 – 70). Number of metastatic sites was one in 23 patients, two in 21, three or more in 10 patients. Most common metastatic sites were bone (67%), lymph nodes (33%), lungs (30%), liver (13%); 13 patients (24%) had bone only disease. Forty-four (81.5%) patients received treatment in first-line, 10 (18.5%) received in second line setting. Median number of cycles applied (including docetaxel/capecitabine combination) was 9 (range 2 – 31, total 576). Median PFS was 9 months (10.4 for hormone receptor positive, 7.3 for negative patients) and median OS was 28 months. Objective response was assessable in 38 patients. Overall response rate (partial + complete response) was 42.6% (95% CI 29.6 – 55.6) with 1 complete response. Toxicities were evaluated in 41 patients; grade 3/4 neutropenia was observed in 10% and grade 3/4 hand-foot syndrome was observed in 24% of patients. Dose reduction was performed in capecitabine in 37%, and in docetaxel in 20% of patients. Conclusions: Maintenance with single agent capecitabine therapy after six cycles of docetaxel/capecitabine chemotherapy is an effective and tolerable treatment option for HER2 negative MBC patients.


2009 ◽  
Vol 27 (15_suppl) ◽  
pp. 595-595
Author(s):  
L. Blakely ◽  
B. Somer ◽  
M. Keaton ◽  
R. Hermann ◽  
F. Schnell ◽  
...  

595 Background: Neoadjuvant (Neo) chemotherapy (CT) with trastuzumab (H) improves pathologic complete response (pCR) rate for HER2+ breast cancer. Dose-dense regimens improve outcome in the adjuvant setting but have not been fully evaluated as preoperative therapy. We designed this regimen to utilize full doses of active agents including docetaxel (T) and H in a novel biweekly schedule to explore efficacy and safety. Methods: Patients (pts) with biopsy proven, clinical stage IIA-IIIC, noninflammatory breast cancer were eligible. HER2+ by FISH was determined locally. CT consisted of epirubicin (E) 100 mg/m2 and cyclophosphamide (C) 600 mg/m2 Q 14 days x 4 followed by T 75 mg/m2 and H 6 mg/kg loading dose, then 4 mg/kg Q 14 days x 4, all with pegfilgrastim support. Surgery was scheduled 20–24 weeks from start after a fifth cycle of H 4mg/kg. EF was measured prior to CT, after EC, after TH and at 6, 12 and 24 months after surgery. Additional adjuvant H to complete 1 year of therapy by conventional schedule was recommended after surgery. The primary endpoint was pCR for invasive cancer in breast and lymph nodes. Results: 30 pts were enrolled at 5 centers: median age was 50.1 (range, 31–72); ethnicity African-American 14, Caucasian 14, other 2; clinical stage IIA, 14, IIB, 4, IIIA, 7, IIIB/C, 5; ER+ 18, PR+ 14; grade 3, 21 and grade 2, 8. Twenty eight pts were evaluable for pathologic response- 2 withdrew before completing treatment, 1 for toxicity. Dose delivery on schedule was >95% for all drugs. Clinical response prior to surgery was cCR 20; cPR 5; and stable 2 pts. Pathologic response: pCR 16 (57%) including 4 with residual DCIS only; 9 pPR, and 2 stable. Mean EF was 63.1 (range, 51–81) before treatment, 62.4 (49–75) after EC and 58.3 (35–74) after TH. Two pts had EF <50% during Neo, one with clinical CHF and 1 additional pt developed CHF during adjuvant single agent H. Both pts had symptomatic improvement with cessation of H. Adverse events were generally mild with 14 grade 3 AEs including 3 episodes of dyspnea and no grade 3 skin toxicity or any grade 4 toxicity noted. Conclusions: Sequential Neo dose-dense Q 14 day EC followed by Q 14 day TH yields a high pCR rate in HER2+ breast cancer with acceptable toxicity profile and no new safety signals noted. No significant financial relationships to disclose.


2020 ◽  
Vol 38 (15_suppl) ◽  
pp. 531-531
Author(s):  
Laura Spring ◽  
Colleen Griffin ◽  
Steven J. Isakoff ◽  
Beverly Moy ◽  
Seth Andrew Wander ◽  
...  

531 Background: Given the success of CDK 4/6 inhibitors for ER+/HER2- metastatic breast cancer, there is much interest in exploring these agents in early breast cancer to potentially reduce recurrence risk. However, tolerability and adherence are important considerations in the adjuvant setting. We evaluated the tolerability and adherence of adjuvant endocrine therapy with the CDK 4/6 inhibitor, ribociclib, in two different schedules, in a prospective phase II clinical trial. Methods: Eligible patients were those with localized stage I-III ER+ (≥ 10%), HER2- breast cancer who had completed surgery and were on adjuvant endocrine therapy with at least one year or more of treatment remaining. Patients were randomized to receive continuous ribociclib (400 mg daily of 28-day cycle; arm 1) or intermittent ribociclib (600 mg daily on days 1-21 of 28-day cycle; arm 2) for one year, in addition to an aromatase inhibitor (plus GnRH agonist if premenopausal). Toxicities were evaluated using CTCAE version 4.03. Adherence was monitored by review of patient diaries and pill count. Results: Of the 81 patients enrolled, 24 discontinued early. The table shows the current status of the patients based on treatment arm (data cut-off as of 1/31/20; updated results will be presented at meeting). A total of 8 serious adverse events (AEs) have occurred thus far: grade 3 transaminitis (1), grade 4 transaminitis (3), grade 3 colitis (1), grade 3 infection (2), and grade 4 lymphopenia (1). The most common grade 3 or greater AEs leading to study discontinuation thus far were transaminitis (8.6%), neutropenia (2.5%), and fatigue (2.5%). No patients discontinued early due to prolonged QTc. Adherence results will be reported at the meeting. Conclusions: Interim results demonstrate that while serious AEs with one year of adjuvant ribociclib are low, a number of patients discontinued adjuvant CDK 4/6 inhibitor. Tolerability and adherence patterns will need to be carefully considered with CDK 4/6 inhibitors in the adjuvant setting. Clinical trial information: NCT03285412 . [Table: see text]


2013 ◽  
Vol 31 (26_suppl) ◽  
pp. 147-147
Author(s):  
Kerry Lynn Reynolds ◽  
XingXing Cheng ◽  
Ashmeet Bhatia ◽  
Michelle Connolly Specht ◽  
Barbara Lynn Smith ◽  
...  

147 Background: Dual neoadjuvant HER2 directed therapy is offered only in a clinical trial setting and is not standard of care, but emerging data suggests targeting multiple mechanisms may be more effective. We conducted a comprehensive systematic review and meta-analysis to evaluate the impact of neoadjuvant dual and single agent HER2 blockade on breast conserving surgery (BCS), and on pathological complete response (pCR) for estrogen receptor (ER)+ and ER- tumors, as well as the impact of pCR on disease-free survival (DFS) and overall survival (OS) for HER2+ breast cancer. Methods: MEDLINE, EMBASE, and Cochrane Controlled Clinical Trials Register databases were queried to identify eligible trials. Inclusion criteria were prospective, neoadjuvant trials that had at least one arm with HER2 directed therapy, and reported pCR. Pooled relative risk ratios (RRs) and p values were estimated for endpoints using the random effects statistical model. Results: We identified 36 trials (N = 4130). High pCR rates (> 40%) were seen with anthracycline-based chemotherapy and trastuzumab alone, and non-anthracycline based dual HER2 blockade. The addition of trastuzumab to chemotherapy did not improve BCS rate (RR 1.40, p = 0.15), but significantly increased rates of pCR (RR 1.91, p = 0.0001). Similarly, dual HER2 blockade compared to trastuzumab alone did not improve BCS rate (RR 1.03, p = 0.84), but significantly increased rates of pCR overall (RR 1.39, p < 0.00001), in both ER+ (RR 1.72, p = 0.01) and ER- subsets (RR 1.91, p = 0.0001), with no increase in grade 3/4 toxicity (RR:1.13, p = 0.16). Dual HER-2 blockade without chemotherapy was associated with pCR in a subset (11.2% - 27%) with minimal toxicity (incidence of grade 3/4 toxicity:1-5%). Higher pCR was associated with improved DFS (RR 2.29, p = 0.006) and OS (RR 4.61, p = 0.009). Conclusions: Neither the addition of trastuzumab to chemotherapy, nor the dual-HER2 blockade compared to trastuzumab, improves rates of BCS. However,both significantly improve rates of pCR, which is associated with improved DFS and OS. Dual HER2 blockade,with endocrine therapy for ER+, could potentially lessen or even obviate the use of chemotherapy.


2019 ◽  
Vol 37 (15_suppl) ◽  
pp. TPS1105-TPS1105
Author(s):  
Aditya Bardia ◽  
Hannah M. Linden ◽  
Gary A. Ulaner ◽  
Sarat Chandarlapaty ◽  
Alice Gosselin ◽  
...  

TPS1105 Background: Endocrine therapy +/- cyclin-dependent kinase 4/6 inhibitors, such as palbociclib, is the standard of care for ER+/HER2- breast cancer. Tumors often become resistant to this combination but retain ER signaling dependence, allowing for sequential ER-directed therapy. Unlike other classes of endocrine therapy with one mode of action, selective ER degraders (SERDs) block signaling by both ER competitive antagonism and degradation, targeting resistance settings that other treatments cannot. SAR439859 is a potent, oral SERD with improved preclinical efficacy and pharmaceutical properties vs other SERDs. This study investigates SAR439859 +/- palbociclib in postmenopausal women with ER+/HER2- metastatic breast cancer. Methods: This prospective, open-label, non-randomized Phase 1/2 study (NCT03284957; TED14856) assesses SAR439859 single agent at dose levels increasing from 20 mg/day up to the maximum administered dose (Part A) followed by cohort expansion at the recommended dose (RD; Part B). The study will also assess two dose levels of SAR439859, in combination with palbociclib 125 mg/day (Days 1–21 in 28-day cycles; Part C) followed by cohort expansion (Part D). Postmenopausal women with ER+/HER2- metastatic breast cancer, who received ≥ 6 months of prior endocrine therapy, are eligible. Patients were permitted to have received ≤ 3 (Part A) or ≤ 1 (Parts B–D) prior chemotherapies for metastatic disease. Exclusion criteria include Eastern Cooperative Oncology Group performance status ≥ 2, concomitant illness (including those related to HIV or hepatitis and other cancers ≤ 3 years) and factors potentially affecting absorption of SAR439859 or palbociclib. Study endpoints include assessment of dose-limiting toxicities, determination of maximum tolerated dose and RD in dose escalation (Parts A and C), and objective response rate according to RECIST v1.1 in dose expansion (Parts B and D). 18FES-PET scan between Days 11–15 in Part A will assess ER availability. Safety, pharmacokinetics and response were evaluated for Parts A–D. Recruitment and screening are ongoing (Part A n = 16; B n = 18; C n = 2; D n = 0). Funding: Sanofi. Clinical trial information: NCT03284957.


2020 ◽  
Vol 38 (15_suppl) ◽  
pp. e15209-e15209
Author(s):  
Peter A. Kaufman ◽  
Sonia Pernas Simon ◽  
Miguel Martin ◽  
Marta Gil-Martin ◽  
Patricia Gomez Pardo ◽  
...  

e15209 Background: Balixafortide (B) is a potent, selective antagonist of the chemokine receptor CXCR4. High CXCR4 levels correlate with aggressive metastatic phenotypes and poor prognosis in metastatic breast cancer (MBC). Efficacy and safety data were published recently from the Phase 1 trial investigating B + eribulin (E) in patients with HER2 negative MBC1. We report the final efficacy analyses from this trial, including assessment of dose-response. Methods: In this single-arm, dose escalation trial, patients (pts) received E + increasing doses of B using a 3+3 design in 3 parts: Part I (cohorts received low E doses); Part II (dose-escalation cohort for B [1−5.5mg/kg] + 1.4mg/m2 E); Expanded Cohort (EC; 5.5mg/kg B + 1.4mg/m2 E) to confirm safety and efficacy. Results: At entry, all 56 women (age range 33−82 years) were HER2-negative (IHC and/or FISH), CXCR4 positive. The majority were Caucasian. Most pts were heavily pre-treated in the metastatic setting (line of chemotherapy on study: 29% 2nd line, 50% 3rd line, 21% 4th line). 75% were hormone receptor positive and 23% had triple negative breast cancer. Conclusions: A consistent dose response effect for B + E was suggested in heavily pretreated pts with HER2 negative MBC across all efficacy endpoints. A comparison of these efficacy results, and particularly response data, with single agent data for E in similar populations2, 3 showed that pts in the EC had a more profound benefit observed consistently throughout all efficacy endpoints. Further data and analysis will be forthcoming for presentation. 1. 3 patients from Part II also included in EC because they received the B dose selected for EC (5.5mg/kg). 2. Part I was an initial safety run-in with lower E doses, and so is not included in the table. 1. Pernas S et al. Lancet Oncol. 2018; 19: 812−24 2. Cortes J et al. Lancet. 2011; 377: 914−923 3. Kaufman PA et al. J Clin Oncol. 2015; 33: 594−601. Clinical trial information: NCT01837095 . [Table: see text]


2021 ◽  
Vol 39 (15_suppl) ◽  
pp. e13025-e13025
Author(s):  
Stephen R. D. Johnston ◽  
Timothy J. Pluard ◽  
Judy S. Wang ◽  
Erika P. Hamilton ◽  
Dejan Juric ◽  
...  

e13025 Background: H3B-6545, a highly Selective ERα Covalent Antagonist (SERCA), inactivates both wild-type and mutant ERα by targeting cysteine 530 and enforcing a unique antagonist conformation. At the dose of 450 mg daily, H3B-6545 has a manageable safety profile and demonstrated preliminary single-agent antitumor activity in heavily pretreated ER+, HER2- mBC patients (Hamilton et al, San Antonio Breast Cancer Symposium, 2020). Methods: The study evaluates the safety, pharmacokinetics (PK), and efficacy of H3B-6545 in combination with palbociclib in patients with ER+, HER2- metastatic breast cancer (MBC). The escalation phase enrolls patients with 2 or more prior therapies in the metastatic setting. Up to one prior chemotherapy and up to one prior CDK4/6 inhibitor were allowed. Results: As of January 31, 2021, 10 patients were enrolled; 7 in Cohort 1 (H3B-6545 300 mg QD and palbociclib 100 mg QD) and 3 in Cohort 2 (H3B-6545 300 mg QD and palbociclib 125 mg QD). One patient in Cohort 1 was not evaluable for dose limiting toxicity (DLT) assessment and no DLT was observed in the 6 evaluable patients. One patient discontinued study treatment because of progression and no patients discontinued study treatment due to adverse events (AE). Grade 3 or 4 neutropenia and thrombocytopenia were observed in 4 patients and 1 patient, respectively. One patient had grade 3 hypercalcemia, generalized muscle weakness, hypophosphatemia, fall, and anemia and one patient had grade 3 lipase increase. Four patients had grade 1 bradycardia or sinus bradycardia (asymptomatic) 1 patient had grade 2 sinus bradycardia (symptomatic, no intervention required). Preliminary PK analysis suggested no clinically relevant drug-drug interactions between H3B-6545 and palbociclib, to be confirmed with data from additional cohorts. Recruitment is currently ongoing in Cohort 2. Updated results will be presented. Conclusions: H3B-6545, in combination with palbociclib, was well-tolerated. Clinical trial information: NCT04288089.


2021 ◽  
Vol 39 (15_suppl) ◽  
pp. e12569-e12569
Author(s):  
Charlie Yang ◽  
Raida Khwaja ◽  
Karen King ◽  
Patricia A. Tang ◽  
Nancy Alice Nixon ◽  
...  

e12569 Background: Biosimilars are defined as medical products that contains a version of the active substance with similar biological characteristics, efficacy, and safety as the original product. Differences however, exist between biosimilars and their original comparator. Unlike small-molecule drugs, identical generic versions cannot be mass produced since manufacturers often have proprietary rights to living cell lines and processes involved in producing biologics. Due to this inherent alteration in production, the potential for clinically meaningful differences may exists. These risks are reduced from bench to clinic through a minimum of one phase 1 study to demonstrate comparability of PK and PD between the biosimilar and the original product, and one phase 3 study to demonstrate equivalency for at least one indication. To date, studies have mainly looked at trastuzumab-dkst in the metastatic setting. This retrospective study compared the pathological complete response (pCR) rates of trastuzumab-dkst to trastuzumab in the neoadjuvant setting for HER2+ early breast cancer (EBC) in Alberta. Methods: Neoadjuvant patients with HER2+ EBC treated with trastuzumab from November 2018 -October 2019 and trastuzumab-dkst from December 2019 - September 2020 were identified. There was no crossover between products. Logistic regression was used to control for variables potentially associated with pCR: trastuzumab product (trastuzumab vs trastuzumab-dkst), age ( < 40 vs 40+), pre-operative T (T1/2 vs T3/4) and N stage (negative vs positive), grade (I/II vs III), HR status (ER and/or PR positive vs ER/PR negative), HER2 (3+ vs SISH+), chemotherapy (anthracycline containing vs not), and chemotherapy completion (yes vs no). Results: 136 patients were identified (56% trastuzumab; 43% trastuzumab-dkst) and there were no significant differences in baseline characteristics except more patients in the trastuzumab-dkst group were clinically N negative; 39% vs 14.3% trastuzumab (p = 0.001). pCR was 35.6% for patients treated with trastuzumab-dkst versus 40.3% with trastuzumab (p = 0.598). In the logistic regression model, there was no significant difference in the odds of a pCR for patients treated with trastuzumab-dkst versus trastuzumab after controlling for the variables selected a priori (OR 1.1, 95% CI 0.5-2.4, p = 0.850). There was a trend for decreased odds of pCR for anthracycline use (OR 0.72 95% CI 0.3-1.6, p = 0.417). Conclusions: pCR rates were similar for patients treated with trastuzumab-dkst compared to trastuzumab in our real world study of HER2+ neoadjuvant EBC and comparable to pivotal phase 3 trials. For a 65 kg patient, the estimated cost savings of trastuzumab-dkst therapy is $22,000, and approximately $240-300 for a non-anthracycline chemotherapy backbone.


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