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Introduction: Activation status of the phosphatidylinositol 3-kinase (PI3K) pathway in breast cancer brain metastases (BCBMs) is largely unknown. We examined expression of phospho(p)-AKT, p-S6, and phosphatase and tensin homologue (PTEN) in BCBMs and their implications for overall survival (OS) and survival after BCBMs. Secondary analyses included PI3K pathway activation status and associations with time to distant recurrence (TTDR) and time to BCBMs. Similar analyses were also conducted among the subset of patients with triple-negative BCBMs.Methods: p-AKT, p-S6, and PTEN expression was assessed with immunohistochemistry in 52 BCBMs and 12 matched primary BCs. Subtypes were defined as hormone receptor (HR)+/HER2-, HER2+, and triple-negative (TNBC). Survival analyses were performed by using a Cox model, and survival curves were estimated with the Kaplan-Meier method.Results: Expression of p-AKT and p-S6 and lack of PTEN (PTEN-) was observed in 75%, 69%, and 25% of BCBMs. Concordance between primary BCs and matched BCBMs was 67% for p-AKT, 58% for p-S6, and 83% for PTEN. PTEN- was more common in TNBC compared with HR+/HER2- and HER2+. Expression of p-AKT, p-S6, and PTEN- was not associated with OS or survival after BCBMs (all, P > 0.06). Interestingly, among all patients, PTEN- correlated with shorter time to distant and brain recurrence. Among patients with TNBC, PTEN- in BCBMs was associated with poorer overall survival.Conclusions: The PI3K pathway is active in most BCBMs regardless of subtype. Inhibition of this pathway represents a promising therapeutic strategy for patients with BCBMs, a group of patients with poor prognosis and limited systemic therapeutic options. Although expression of the PI3K pathway did not correlate with OS and survival after BCBM, PTEN- association with time to recurrence and OS (among patients with TNBC) is worthy of further study. [ABSTRACT FROM AUTHOR]

Background: Alpelisib is an oral α-specific class I PI3K inhibitor approved in combination with fulvestrant for the treatment of PIK3CA-mutated hormone receptor-positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer. The tolerability of this drug with the oral chemotherapy capecitabine is unknown., Patients and Methods: This phase I trial evaluated the dose-limiting toxicities (DLTs) and maximum tolerated dose (MTD) of alpelisib (250 mg or 300 mg daily for 3-weeks) with capecitabine (1000 mg/m 2 twice daily for 2-weeks followed by a 1-week rest period) in patients with metastatic HER2-negative breast cancer, regardless of PIK3CA mutation status., Results: Eighteen patients were treated with alpelisib-capecitabine. Half of the patients had HR+ breast cancer, and 16 had prior systemic therapy for metastatic disease. The MTD of alpelisib was 250 mg daily in combination with capecitabine 1000 mg/m 2 twice daily. DLTs included hyperglycemia, QTc prolongation, fatigue, and chest pain. The most common grade 3 adverse event (AE) was hyperglycemia (28%). No grade 4 AEs were observed. Three patients discontinued therapy due to an AE. One-third of patients required dose reduction of both alpelisib and capecitabine. Four patients experienced a partial response and 8 patients experienced stable disease. The median progression-free survival was 9.7 months (95% CI 2.8-13.5 months) and median overall survival was 18.2 months (95% CI 7.2-35.2 months). Twelve patients had PIK3CA mutation testing completed, of these 2 had known or likely deleterious PIK3CA mutation., Conclusion: This study provides safety data for an oral combination therapy of alpelisib-capecitabine and defines tolerable doses for further study., Competing Interests: Disclosure YA reports consulting income from Exact Sciences, AstraZeneca and Pfizer. C.K.A. reports research funding provided by PUMA, Lilly, Merck, Seattle Genetics, Nektar, Tesaro, G1-Therapeutics, ZION, Novartis, Pfizer, Astra Zeneca, Elucida, Caris, Incyclix; consulting for Genentech, Eisai, IPSEN, Seattle Genetics, Astra Zeneca, Novartis, Immunomedics, Elucida, Athenex, Roche; royalties from UpToDate, Jones and Bartlett. L.A.C. reports research funding from Genentech/Roche, AstraZeneca, Lilly, Novartis, Veracyte, Nanostring. C.M.P. is an equity stockholder and board of director member of BioClassifer LLC and is listed as inventor on patent applications for the Breast PAM50 assay. E.C.D. reports consulting income from Sanofi, research funding from Novartis, Genentech, Bayer, Pfizer, and Merck and a family member who received past consulting income from Novartis. L.A.C reports research funding from AstraZeneca, Genentech/Roche, Lilly, Merck, Nanostring, Novartis, SeaGen, and Veracyte. P.K.M. is a full-time employee and equity stockholder with Veracyte., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The objective of the study is to assess impact of systemic disease (SD) status on overall survival and brain metastasis (BM) control, adopting a novel landmark approach to categorize SD among breast cancer (BC) patients. This single institution retrospective study included BCBM patients who have received stereotactic radiosurgery (SRS) to brain. Separate endpoints [CNS failure-free survival (cFFS), overall survival (OS)] were analyzed from each Landmark (LM): LM1 (3-months), LM2 (6-months). Patients were categorized into early and non-early progression (EP, NEP) groups depending on SD status before LMs. Median survivals from LM were assessed with Kaplan Meier plots, compared with Log-Rank test. EP was associated with worse median cFFS and OS vs NEP in both LM analyses (cFFS- LM1: 3.6 vs. 9.7 months, p = 0.0016; LM2: 2.3 vs. 12.5 months, p < 0.0001; OS- LM1: 3.6 vs. 24.3 months, p < 0.0001; LM2: 5.3 vs. 30.2 months, p < 0.0001). In multivariate analyses, EP was associated with shorter cFFS [LM1: Hazard Ratio (HR) with 95% confidence interval (CI) 3.16, 1.46-6.83, p = 0.0034; LM2: 5.32, 2.33-12.15, p = <0.0001] and shorter OS (LM1: HR with 95% CI 4.28, 1.98-9.12, p = 0.0002; LM2: 7.40, 3.10-17.63, p = <0.0001) vs NEP. Early systemic disease progressions after 1st SRS to brain is associated with worse cFFS and OS in patients with BCBM., (© 2024. The Author(s).)

Background: Although serum circulating tumor DNA (ctDNA) is routine, data from patients with brain metastases (BrMs) is limited. We assessed genomic alterations in ctDNA from patients with solid tumor BrMs in 3 groups: Isolated BrMs with stable extracranial disease (iCNS), concurrent brain and extracranial progression (cCNS), and extracranial progression with no active BrMs (eCNS). We also compared ctDNA alterations between patients with and without BrMs., Methods: Patients with a Guardant360 ctDNA profile with ( n  = 253) and without BrMs ( n  = 449) from the Duke Molecular Registry between January 2014 and December 2020 were identified. Actionable alterations were defined as FDA-recognized or standard-of-care biomarkers. Disease status was determined via investigator assessment within 30 days of ctDNA collection., Results: Among the 253 patients with BrMs: 29 (12%) had iCNS, 160 (63%) cCNS, and 64 (25%) eCNS. Breast (BC; 12.0%) and non-small cell lung cancer (NSCLC; 76.4%) were the most common tumor types. ESR1 (60% vs 25%, P  < .001) and BRCA2 (17% vs 5%, P  = .022) were more frequent in BC BrMs. In NSCLC BrMs, EGFR alterations were most frequent in the iCNS group (iCNS: 67%, cCNS: 40%, eCNS:37%, P  = .08) and in patients with BrMs (36% vs 17%, P  < .001). Sequencing from both brain tissue and ctDNA were available for 8 patients; 7 (87.5%) had identical alterations., Conclusions: This study illustrates the feasibility of detecting alterations from ctDNA among patients with BrMs. A higher frequency of actionable mutations was observed in ctDNA in patients with BrMs. Additional studies comparing ctDNA and alterations in BrMs tissue are needed to determine if ctDNA can be considered a surrogate to support treatment decisions., Competing Interests: No disclaimers. No funding., (© The Author(s) 2024. Published by Oxford University Press, the Society for Neuro-Oncology and the European Association of Neuro-Oncology.)

The treatment of metastatic breast cancer (MBC) has improved over the past decade, however prognosis continues to be mitigated by the fact that about 1 in 5 patients with MBC will develop brain metastases (BrM) during their metastatic disease course. 1 This number is even higher for patients with triple-negative breast cancer (TNBC), with studies showing as high as 40% of patients developing BrM. 2, 3 Studies have shown that TNBC portends a worse survival after a diagnosis of BrM compared with non-TNBC subtypes. 4 Given the unique location and biologic properties of BrM, treatment options have historically been limited. Challenges to the treatment of TNBC BrM include a lack of targeted therapies and difficulties in delivery of drug to the brain past the blood-brain barrier (BBB). Herein, we will review the advances in local and systemic therapies to most effectively treat patients with TNBC BrM, including therapies on the horizon currently in clinical trials., Competing Interests: Disclosure CKA: Research funding PUMA, Lilly, Merck, Seattle Genetics, Nektar, Tesaro, G1-Therapeutics, ZION, Novartis, Pfizer, Astra Zeneca, Elucida, Caris; Consulting: Genentech, Eisai, IPSEN, Seattle Genetics, Astra Zeneca, Novartis, Immunomedics, Elucida, Athenex. Royalties: UpToDate, Jones and Bartlett., (Copyright © 2023. Published by Elsevier Inc.)

Brain metastases are an increasing global public health concern, even as survival rates improve for patients with metastatic disease. Both metastases and the sequelae of their treatment are key determinants of the inter-related priorities of patient survival, function, and quality of life, mandating a multidimensional approach to clinical care and research. At a virtual National Cancer Institute Workshop in September, 2022, key stakeholders convened to define research priorities to address the crucial areas of unmet need for patients with brain metastases to achieve meaningful advances in patient outcomes. This Policy Review outlines existing knowledge gaps, collaborative opportunities, and specific recommendations regarding consensus priorities and future directions in brain metastases research. Achieving major advances in research will require enhanced coordination between the ongoing efforts of individual organisations and consortia. Importantly, the continual and active engagement of patients and patient advocates will be necessary to ensure that the directionality of all efforts reflects what is most meaningful in the context of patient care., Competing Interests: Declaration of interests TSA, DKS, PSS, JAH, MGE, JSB-S, PGP, CNC, and MMA are employees of the US National Institutes of Health. BME received consulting fees from Medicenna, MedQIA, Servier, Chimerix, Sumitomo Dainippon Pharma Oncology, ImmunoGenesis, Ellipses Pharma, Alpheus Medical, Curtana Pharma, Sagimet Biosciences, and Sapience Therapeutics; and other support from Siemens. SCF received grants from Siemens and Neosoma; consulting fees from Medicenna, MedQIA, Servier, Chimerix, Sumitomo Dainippon Pharma Oncology, ImmunoGenesis, Ellipses Pharma, Alpheus Medical, Curtana Pharma, Sagimet Biosciences, and Sapience Therapeutics; and other services from Siemens. AAA received grants from Varian and NH TheraAguix, and consulting fees from Novartis and Seagen. DMT received grants from Varian Medical Systems, Blue Earth Diagnostics, and NovoCure, and consulting fees from Boston Scientific. RK received grants from Medtronic, Blue Earth Diagnostics, NovoCure, GT Medical Technologies, AstraZeneca, Exelixis, Viewray, Brainlab, and Cantex Pharmaceuticals; consulting fees from Kazia Therapeutics, Elekta, Viewray, Castle Biosciences, and NovoCure; travel support from Elekta, Accuray, NovoCure, and Peerview Institute for Medical Education; other support from Elekta, Accuray, Novocure, and the Peerview Institute for Medical Education; and is on the Viewray Medical Advisory Board. CKA received grants from PUMA, Lilly, Merck, Seattle Genetics, Nektar, Tesaro, G1-Therapeutics, ZION, Novartis, Pfizer, AstraZeneca, Elucida, and Caris; licences from UpToDate and Jones and Bartlett; other support from Genentech, Eisai, IPSEN, Seattle Genetics, AstraZeneca, Novartis, Immunomedics, Elucida, and Athenex; and is on the Genentech board. PWS received consulting fees from Varian. JH-G has funding from the National Institutes of Health (NIH)/National Cancer Institute (NCI) and received payment for a lecture from Aptitude Health. DNY has a Robert Wood Johnson Foundation Medical Grant and Brockman Foundation Medical Grant. ICGO received grants from Bristol Myers Squibb, Merck, and Pfizer; and consulting fees from Bristol Myers Squibb, Array, Novartis, Sintetica, and Leal Therapeutics. AM received grants from Eisai/H3B Pharmaceutical, Takeda Millenium Pharm, Lilly, Pfizer, MTEM, Merck, Roche, Zion, Norvatis, Dantari, and Genentech; payment from Taiho; research support from Tempus and PUMA; and was on the boards for Seagen and Eli Lilly. EG received grants from Celgene, Denovo Biopharma, MedImmune, and Servier Pharmaceuticals; and is on the boards for Karyopharm Therapeutics, Kiyatec, and Boston Scientific. VG received grants from ImmunoChem Therapeutics. PKB received grants from Mirati, Eli Lilly, Kinnate, Merck, NIH, the Breast Cancer Research Foundation, Damon Runyon, AACR, the Terry and Jean de Gunzburg MGH Research Scholar Fund, and the Demetra fund; consulting fees from Axiom Healthcare, Pfizer, Dantari, Advice Connect inspire, ElevateBio, Sintetica, SK Life Sciences, Voyager Therapeutics, Kazia, MPM Capital, Medscape, Eli Lilly, and Tesaro; other payments from Medscape and Pfizer; other support from GSK, Genentech-Roche, Eli Lilly, AstraZeneca, Kazia, Merck, Mirati, and Pfizer; and was the Chair of Society of Annual Neuro-Oncology Meetings. LC has grants from CDC/Johns Hopkins, DSI, Hological, and Myriad; US patent US7734496B1; stock from UNH; and a leadership role at Touch4Life and MD HBEB. MPM received consulting fees from Kazia, Novocure, Zap, Xoft, Karyopharm, and Sapience; has stocks at Oncoceutics and Chimerix; and is on the boards for Mevion, Oncoceutics, and Xcision. MK received grants from AbbVie, Bristol Myers Squibb, Daiichi Sankyo, BioNTech, CNS pharmaceuticals, Immorna Therapeutics, Celldex Therapeutics, and Astellas; consulting fees from Novocure and George Clinical; miscellaneous payment from Jax Lab, GSK, Voyager Therapeutics, and Johnson and Johnson; and is on the board for Berg Pharmaceuticals. MSA received grants from Seagen, AstraZeneca, Bristol Myers Squibb, Bayer, Incyte, Pharmacyclics, Novocure, Mimivax, and Merck; consulting fees from Bayer, Novocure, Kiyatec, Insightec, GSK, Xoft, Nuvation, Cellulartity, SDP Oncology, Apollomics, Prelude, Janssen, Tocagen, Voyager Therapeutics, Viewray, Caris Lifesciences, Pyramid Biosciences, Anheart Therapeutics, Varian Medical Systems, Theraguix, and Menarini Ricerche; has stocks from Mimivax, Cytodyn, and Medlnnovate Advisors; and is on the boards for Cairn Therapeutics, Pyramid Biosciences, Modifi Biosciences, and Bugworks. MHG has grant number U54CA261717 from the NIH/NCI and received consulting fees from Midatech. JL has research funding from Bristol Myers Squibb. MMK has a grant (number R50CA276015) from the NIH/NCI and Blue Earth Diagnostics; and is on the boards for the NCCN CNS Cancers Guidelines Committee, International Journal of Radiation Oncology*Biology*Physics, Neuro-Oncology, and the External Advisory Board for Stanford U54 MetNet. JR received grants from Black Diamond Therapeutics, Blueprint Medicines, Hummingbird, Merck Sharp & Dohme, Vall d’Hebron Institute of Oncology/Cancer Core Europe, Yingli, AadiBioscience, Amgen, Bayer, Bicycle Therapeutics, BioAtla, BioMed Valley Discoveries, Cellestia, Curis, CytomX, Deciphera, ForeBio, GenMab, GlaxoSmithKline, Hummingbird, Hucthinson MediPharma, Ideaya, Kelun-Biotech, Linnaeus Therapeutics, Loxo Oncology, Merus, Mirati, Novartis, Nuvation, Pfizer, Roche Pharmaceuticals, Spectrum Pharmaceuticals, Symphogen, Taiho, Takeda-Millennium, and Tango Therapeutics; consulting fees from Alnylam Pharmaceuticals, Avoro Capital Advisors, Boxer Capital, the Chinese University of Hong Kong, Clarion Healthcare, Columbus Venture Partners, Cullgen, Debiopharm, Incyte, Macrogenics, Merus, Monte Rosa Therapeutics, Oncology One, Pfizer, Sardona Therapeutics, Tang Advisors, and the Vall d’Hebron Institute of Oncology/Ministero De Empleo Y Seguridad Social; travel support from European Society for Medical Oncology; is on boards for AadiBioscience, Ellipses Pharma, Envision Pharma Limited, Incyte, IONCTURA, Merus, and Monte Rosa Therapeutics; and is on the steering committee for the Vall d’Hebron Institute of Oncology/Ministero De Empleo Y Seguridad Social. AB received support from NIH grant number P30 CA008748, has four US patents, and is on the Evren Technologies Scientific Advisory Board. HT has grants from BMS Bristol Myers Squibb, Novartis, Merck, Genentech, Eisai, GSK, RAPT, and Dragonfly; and received consulting fees from BMS Bristol Myers Squibb, Novartis, Merck, Genentech, Eisai, Iovance, Pfizer, Karyopharm, Boxer Capital, Jazz Pharma, and Medicenna. All other authors declare no competing interests., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Previous work from our group and others has shown that patients with breast cancer can generate a T cell response against specific human epidermal growth factor 2 (HER2) epitopes. In addition, preclinical work has shown that this T cell response can be augmented by Ag-directed mAb therapy. This study evaluated the activity and safety of a combination of dendritic cell (DC) vaccination given with mAb and cytotoxic therapy. We performed a phase I/II study using autologous DCs pulsed with two different HER2 peptides given with trastuzumab and vinorelbine to a study cohort of patients with HER2-overexpressing and a second with HER2 nonoverexpressing metastatic breast cancer. Seventeen patients with HER2-overexpressing and seven with nonoverexpressing disease were treated. Treatment was well tolerated, with one patient removed from therapy because of toxicity and no deaths. Forty-six percent of patients had stable disease after therapy, with 4% achieving a partial response and no complete responses. Immune responses were generated in the majority of patients but did not correlate with clinical response. However, in one patient, who has survived >14 y since treatment in the trial, a robust immune response was demonstrated, with 25% of her T cells specific to one of the peptides in the vaccine at the peak of her response. These data suggest that autologous DC vaccination when given with anti-HER2-directed mAb therapy and vinorelbine is safe and can induce immune responses, including significant T cell clonal expansion, in a subset of patients., (Copyright © 2023 by The American Association of Immunologists, Inc.)

Opinion Statement: In 2023, breast cancer brain metastases (BCBrM) remain a major clinical challenge gaining well-deserved attention. Historically managed with local therapies alone, systemic therapies including small molecule inhibitors and antibody-drug conjugates (ADCs) have shown unprecedented activity in recent trials including patients with brain metastases. These advancements stem from efforts to include patients with stable and active BCBrM in early- and late-phase trial design. Tucatinib added to trastuzumab and capecitabine improves intracranial and extracranial progression-free survival and overall survival in stable and active human epidermal growth factor receptor 2 (HER2+)-positive brain metastases. Trastuzumab deruxtecan (T-DXd) has both shown impressive intracranial activity in stable and active HER2+ BCBrMs challenging historical thinking of ADCs' inability to penetrate the central nervous system (CNS). T-DXd has shown potent activity in HER2-low (immunohistochemistry scores of 1+ or 2+, non-amplified by fluorescence in situ hybridization) metastatic breast cancer and will be studied in HER2-low BCBrM as well. Novel endocrine therapies including oral selective estrogen downregulators (SERDs) and complete estrogen receptor antagonists (CERANs) are being studied in hormone receptor-positive BCBrM clinical trials due to robust intracranial activity in preclinical models. Triple-negative breast cancer (TNBC) brain metastases continue to portend the worst prognosis of all subtypes. Clinical trials leading to the approval of immune checkpoint inhibitors have enrolled few BCBrM patients leading to a lack of understanding of immunotherapies contribution in this subgroup. Data surrounding the use of poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors in patients with germline BRCA mutation carriers with CNS disease is hopeful. ADCs including those targeting low-level HER2 expression and TROP2 are under active investigation in triple-negative BCBrMs., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

For three years, COVID-19 has circulated among our communities and around the world, fundamentally changing social interactions, health care systems, and service delivery. For people living with (and receiving treatment for) cancer, pandemic conditions presented significant additional hurdles in an already unstable and shifting environment, including disrupted personal contact with care providers, interrupted access to clinical trials, distanced therapeutic encounters, multiple immune vulnerabilities, and new forms of financial precarity. In a 2020 perspective in this journal, we examined how COVID-19 was reshaping cancer care in the early stages of the pandemic and how these changes might endure into the future. Three years later, and in light of a series of interviews with patients and their caregivers from the United States and Australia conducted during the pandemic, we return to consider the potential legacy effects of the pandemic on cancer care. While some challenges to care provision and survivorship were unforeseen, others accentuated and amplified existing problems experienced by patients, caregivers, and health care providers. Both are likely to have enduring effects in the "post-pandemic" world, raising the importance of focusing on lessons that can be learned for the future., (©2023 The Authors; Published by the American Association for Cancer Research.)

Purpose: Preclinical data showed that prophylactic, low-dose temozolomide (TMZ) significantly prevented breast cancer brain metastasis. We present results of a phase I trial combining T-DM1 with TMZ for the prevention of additional brain metastases after previous occurrence and local treatment in patients with HER2+ breast cancer., Patients and Methods: Eligible patients had HER2+ breast cancer with brain metastases and were within 12 weeks of whole brain radiation therapy (WBRT), stereotactic radiosurgery, and/or surgery. Standard doses of T-DM1 were administered intravenously every 21 days (3.6 mg/kg) and TMZ was given orally daily in a 3+3 phase I dose escalation design at 30, 40, or 50 mg/m2, continuously. DLT period was one 21-day cycle. Primary endpoint was safety and recommended phase II dose. Symptom questionnaires, brain MRI, and systemic CT scans were performed every 6 weeks. Cell-free DNA sequencing was performed on patients' plasma and CSF., Results: Twelve women enrolled, nine (75%) with prior SRS therapy and three (25%) with prior WBRT. Grade 3 or 4 AEs included thrombocytopenia (1/12), neutropenia (1/12), lymphopenia (6/12), and decreased CD4 (6/12), requiring pentamidine for Pneumocystis jirovecii pneumonia prophylaxis. No DLT was observed. Four patients on the highest TMZ dose underwent dose reductions. At trial entry, 6 of 12 patients had tumor mutations in CSF, indicating ongoing metastatic colonization despite a clear MRI. Median follow-up on study was 9.6 m (2.8-33.9); only 2 patients developed new parenchymal brain metastases. Tumor mutations varied with patient outcome., Conclusions: Metronomic TMZ in combination with standard dose T-DM1 shows low-grade toxicity and potential activity in secondary prevention of HER2+ brain metastases., (©2023 American Association for Cancer Research.)

Successful drug development for people with cancers of the CNS has been challenging. There are multiple barriers to successful drug development including biological factors, rarity of the disease, and ineffective use of clinical trials. Based upon a series of presentations at the First Central Nervous System Clinical Trials Conference hosted by the American Society of Clinical Oncology and the Society for Neuro-Oncology, we provide an overview on drug development and novel trial designs in neuro-oncology. This Review discusses the challenges of therapeutic development in neuro-oncology and proposes strategies to improve the drug discovery process by enriching the pipeline of promising therapies, optimising trial design, incorporating biomarkers, using external data, and maximising efficacy and reproducibility of clinical trials., Competing Interests: Declaration of interests RR has received research support from Project Data Sphere and personal fees from St Lucia Consulting, outside the submitted work;and has been supported by the Joint Center for Radiation Therapy Foundation Grant. CKA has received research support from Puma Biotechnology, Lilly, Merck, Seattle Genetics, Nektar, Tesaro, G1-Therapeutics, Zion Pharmaceuticals, Novartis Pharmaceuticals, Pfizer, AstraZeneca, and Elucida; served as consultant for Genentech, Eisai, IPSEN, Seattle Genetics, AstraZeneca, Novartis Pharmaceuticals, Immunomedics, Elucida, and Athenex; and received royalties from UpToDate, Jones & Bartlett. HAT received personal fees from Novartis Pharmaceuticals; grants and personal fees from Bristol Myers Squibb, Roche, and Genentech; and grants from Merck and Celegene, outside the submitted work. MM reports personal fees from KaryoPharm, Mevio, Zapprx, Sapience, and Xoft outside the submitted work. He reports participation in the board of directors for Oncoceutics and stock ownership in Chimerix. PYW has received research support from AstraZeneca, BeiGene, Celgene, Chimerix, Eli Lily, Genentech, Roche, Kazia, MediciNova, Merck, Novartis Pharmaceuticals, Nuvation Bio, Puma, Servier, Vascular Biogenics, and Variation Biotechnologies Vaccines; and is on advisory boards for AstraZeneca, Bayer, Black Diamond, Boehringer Ingelheim, Boston Pharmaceuticals, Celularity, Chimerix, Day One Bio, Genenta, GlaxoSmithKline, Karyopharm, Merck, Mundipharma, Novartis Pharmaceuticals, Novocure, Nuvation Bio, Prelude Therapeutics, Sapience, Servier, Sagimet, Vascular Biogenics, and VBI Vaccines. JdG reports grant or research support from Sanofi-Aventis, AstraZeneca, EMD-Serono, Eli Lilly, Novartis, Deciphera Pharmaceuticals, and Mundipharma; paid consultancies from Celldex, Deciphera Pharmaceuticals, AbbVie, FivePrime Therapeutics, GW Pharmaceuticals, Carthera, Eli Lilly, Kadmon, Boston Biomedical, Taiho Pharmaceuticals, Kairos Venture Investments, Syneos Health, Monteris, Agios, Mundipharma Research, GenomiCare, Blue Earth Diagnostics, Del Mar Pharmaceuticals, Insightec, Voyager Therapeutics, Merck, Tocagen, Bioasis Technologies, and ResTORbio; advisory board membership for Genentech, Celldex, Foundation Medicine, Novogen, Deciphera, AstraZeneca, Insys Therapeutics, Merck, Eli Lilly, Novella Clinical, Karyopharm Therapeutics, Blue Earth Diagnostics, Kiyatec, Vanquish Oncology, Orsenix, Insightec, Prelude Therapeutics, Debiopharm Therapeutics, and Janssen Global Services; data safety monitoring board membership for VBL Therapeutics (VB111; glioblastoma), Novella (ICT-107; glioblastoma), and VBI Vaccines (VBI-1901; glioblastoma); stock ownership in Ziopharm Oncology and Gilead; and company employment (spouse) in Ziopharm Oncology. EG has received honoraria for advisory board participation from Kiyatec (personal compensation), and Karyopharm Therapetuics for data safety and monitoring board participation (compensation to employer). Her institution has received grant funding from Servier Pharmaceuticals, Celgene, MedImmune, and Tracon Pharmaceuticals; and she has been supported by the National Cancer Institute of the National Institutes of Health (NIH) under award numbers UG1CA189823 (Alliance for Clinical Trials in Oncology), R01 CA258239, U19 CA264362, and The Ben and Catherine Ivy Foundation. MK reports research funding paid to their institution from BMS, AbbVie, Biontech, Astellas, Celldex, Daiichi Sankyo, and CNS pharmaceuticals; and honoraria from George Clinical, Voyager Therapeutics, Johnson & Johnson, and the Jax lab for genomic research; and is supported by NIH grants (U01-NS090284-05, U19-CA264385-01, P50CA190991-08, P01-CA225622-04, and R01-CA235612-03). M-YCP has been supported by the National Cancer Institute of the NIH under award number U10 CA180822 (NRG Oncology—Statistics and Data Management Center). All other authors declare no competing interests., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Leptomeningeal metastases (LM) are a devastating complication of HER2 + metastatic breast cancer (MBC), with no effective treatments. In a case series of 8 patients with heavily pretreated HER2 + MBC and progressing LM, all 8 patients (100%) derived clinical benefit from Trastuzumab deruxtecan (TDXd), and 4 patients (50%) had an objective partial response based on formal neuroradiology MRI reads using the EORTC/RANO-LM Revised-Scorecard. T-DXd warrants further study in LM in HER2 + MBC and solid tumors where T-DXd may be active., (© 2023. The Author(s).)

Background: Poly(ADP-ribose) polymerase (PARP) inhibitors are effective in germline BRCA1 or BRCA2 (BRCA1/2) mutation-associated metastatic breast cancer. However, studies evaluating PARP inhibitors plus platinum-based chemotherapy in germline BRCA1/2-wildtype triple-negative breast cancer are scarce. A large proportion of germline BRCA1/2-wildtype triple-negative breast cancer shows homologous recombination deficiency (HRD), resulting in a BRCA-like phenotype that might render sensitivity to PARP inhibitors. The S1416 trial assessed the efficacy of cisplatin combined with the PARP inhibitor veliparib in three predefined groups of metastatic breast cancer: germline BRCA1/2-mutated, BRCA-like, and non-BRCA-like., Methods: S1416 was a randomised, double-blind, placebo-controlled, phase 2 trial conducted at 154 community and academic clinical sites across the USA. Eligible patients aged 18 years or older had metastatic or recurrent triple-negative breast cancer or germline BRCA1/2-associated metastatic or recurrent breast cancer, an Eastern Cooperative Oncology Group performance status of 0-2, and had received up to one line of chemotherapy for metastatic disease. Patients were randomly assigned (1:1) via the National Clinical Trials Network open interactive system with dynamic balancing on number of previous cytotoxic regimens for metastatic disease to receive intravenous cisplatin (75 mg/m 2 , day 1) combined with either veliparib or matching placebo (300 mg orally twice a day, days 1-14) on a 21-day cycle. Investigators, patients, and the sponsors were masked to treatment assignment; the study statisticians were unmasked. Central testing after ran domisation classified patients as having mutated or wildtype germline BRCA1/2. A biomarker panel established a priori was used to classify patients with wildtype germline BRCA1/2 into BRCA-like and non-BRCA-like phenotype groups, with BRCA-like status based on at least one of the biomarkers: genomic instability score (≥42), somatic BRCA1/2 mutations, BRCA1 promoter methylation, or non-BRCA1/2 homologous recombination repair germline mutations. The primary endpoint was investigator-assessed progression-free survival, analysed separately for the three predefined biomarker groups with a prespecified α value for each analysis. Efficacy analyses were done by intention to treat and included all eligible patients. Safety analyses of toxicities attributed to treatment included all patients who received at least one dose of veliparib or placebo. The study is ongoing and registered with ClinicalTrials.gov, NCT02595905., Findings: Between July 7, 2016, and June 15, 2019, 335 patients were enrolled and randomly assigned. 320 patients (n=162 to cisplatin plus veliparib, all women; and n=158 to cisplatin plus placebo, 157 women and one man) were eligible for efficacy evaluation. 247 patients were classified into the three biomarker groups: germline BRCA1/2-mutated (n=37), BRCA-like (n=101), and non-BRCA-like (n=109). 73 patients could not be classified due to missing biomarker information. Median follow-up was 11·1 months (IQR 5·6-20·8). In the germline BRCA1/2-mutated group, median progression-free survival was 6·2 months (95% CI 2·3-9·2) in the cisplatin plus veliparib group and 6·4 months (4·3-8·2) in the cisplatin plus placebo group (HR 0·79 [95% CI 0·38-1·67]; log-rank p=0·54). In the BRCA-like group, median progression-free survival was 5·9 months (95% CI 4·3-7·8) in the cisplatin plus veliparib group versus 4·2 months (2·3-5·0) in the cisplatin plus placebo group (HR 0·57 [95% CI 0·37-0·88]; p=0·010). In the non-BRCA-like group, median progression-free survival was 4·0 months (95% CI 2·5-4·7) in the cisplatin plus veliparib group versus 3·0 months (2·2-4·4) in the cisplatin plus placebo group (HR 0·89 [95% CI 0·60-1·33]; p=0·57). The most common grade 3 or worse adverse events attributed to treatment were neutropenia (71 [46%] of 155 patients in the cisplatin plus veliparib group vs 29 [20%] of 147 in the cisplatin plus placebo group), leukopenia (42 [27%] vs 11 [7%]), anaemia (35 [23%] vs 12 [8%]), and thrombocytopenia (29 [19%] vs four [3%]). Serious adverse events attributed to treatment occurred in 48 (31%) patients in the cisplatin plus veliparib group and 53 (36%) patients in the cisplatin plus placebo group. Treatment-related adverse events led to death in one patient in the cisplatin plus veliparib group (sepsis) and one patient in the cisplatin plus placebo group (acute kidney injury due to cisplatin plus heart failure from previous doxorubicin exposure)., Interpretation: The addition of veliparib to cisplatin significantly improved progression-free survival in patients with BRCA-like metastatic triple-negative breast cancer, but not in patients with non-BRCA-like metastatic breast cancer. PARP inhibitors combined with platinum-based chemotherapy should be explored further in BRCA-like triple-negative breast cancer., Funding: National Cancer Institute and National Institute of General Medical Sciences (US National Institutes of Health); AbbVie; Myriad Genetics; the Biomarker, Imaging, and Quality of Life Studies Funding Program (awarded by the National Cancer Institute); and The University of Kansas Cancer Center., Competing Interests: Declaration of interests PS reports an S1416 subaward from SWOG (payments made to the institution) as support for the present work; other relationships include grants (payments made to the institution) from Novartis, Bristol Myers Squibb, Merck, and Gilead; royalties from UpToDate; and advisory board participation for Pfizer, Merck, Gilead, Genzyme Corporation, Novartis, AstraZeneca, GSK, and Seattle Genetics. WEB reports a grant from the US National Cancer Institute (payments made to the institution) as support for the present work; other relationships include grants (payments made to the institution) from Merck and AstraZeneca; and data safety monitoring board participation for Frontier Science and the National Eye Institute. JRG reports steering committee membership for Genentech (Roche); advisory board participation for AstraZeneca and Puma Biosciences; consulting fees from Seagen; data safety monitoring board or advisory board participation (no compensation) for Genentech, AstraZeneca, Novartis, and Immunomedics; and a role as Chief Medical Officer for the American Society of Clinical Oncology. SLP reports grants (payments made to the institution) from Pfizer, AstraZeneca, Puma Biosciences, Medivation, Genentech, Eli Lilly, and Bayer HealthCare Pharmaceuticals; faculty or speaker payment from Pfizer; and steering committee membership (no compensation) for Genentech and AbbVie. CKA reports grants from Puma Biosciences, Lilly, Merck, Seattle Genetics, Nektar, Tesaro, G1-Therapeutics, Zion Pharma China, Novartis, Pfizer, AstraZeneca, and Elucida; royalties or licenses from UpToDate and Jones and Bartlett Publishing Company; consulting fees from Genentech, Eisai, Seattle Genetics, AstraZeneca, Novartis, Immunomedics, Elucida, and Athenex; and data safety monitoring board or advisory board participation for Genentech. LG reports grants (payments made to the institution) from Genentech and Merck; advisory board participation for Genentech, Merck, AstraZeneca, Novartis, Syndax, Biovica, GE Healthcare, Pfizer, Nanostring, Immunomedics, Aduro, Genomic Health, Amgen, Mylan-Lynx, Eisai, Lilly, Exact Sciences, and Biovica; and data safety monitoring board participation for Daiichi Sankyo. DT reports grants from Novartis, Pfizer, and Polyphor; and consulting fees from AstraZeneca, GSK, Exact Sciences, Gilead, Novartis, Pfizer, Personalis, and Sermonix. UAB-G reports consulting fees from Novartis, Biotheranostics, Taiho, Sanofi, Macrogenics, Seattle Genetics, and Gilead; and payment or honoraria from Seattle Genetics. AKG reports a Masonic Cancer Alliance Partners Advisory Board grant from The University of Kansas Cancer Center and Children's Mercy Kansas City as support for the current work; other relationships include grants (payments made to the institution) from VITRAC Therapeutics and Predicine; scientific advisory board membership for Biovica, Clara Biotech, and Sinochips Diagnostics; a role as Deputy Director for The University of Kansas Cancer Center; a role as co-founder of Sinochips Diagnostics; and future stock options with Clara Biotech. EMS reports a SWOG subcontract from the Biomarker, Imaging, and Quality of Life Studies Funding Program as support for the current work; and data safety monitoring board participation for Novartis. KMT reports homologous recombination deficiency patents, employment, and stock or stock options with Myriad Genetics. LP reports research funding or clinical trial support from Bristol Myers Squibb, Merck, Pfizer, AstraZeneca, and Seagen. DFH reports grants (payments made to the institution) from Merrimack Pharmaceuticals (Parexel), Menarini Silicon Biosystems, Pfizer, AstraZeneca, and Cepheid; royalties or licenses from Janssen Research & Development (Johnson & Johnson; transferred to Menarini Silicon Biosystems); consulting fees from Cepheid, Freenome, Artiman Ventures (Cellworks), Lexent Bio, Epic Sciences, L-Nutra, BioVeca, OncoCyte, Turnstone Biologics, Predictus BioSciences, Guardant, Macrogenics, Xilis, and Exact Sciences; lecture payment from Tempus and Macrogenics; patents under Immunicon Corporation (European Patent Office) and University of Michigan (US Patent Office); a role as chair for the International Breast Cancer Study Group; stock options with Inbiomotion; receipt of equipment, materials, drugs, medical writing, gifts, or other services from Menarini Silicon Biosystems and Cepheid; and other financial or non-financial interests from UpToDate (section editor) and CancerExpertNow. All other authors declare no competing interests., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Purpose: Current systemic therapy guidelines for patients with HER2 + breast cancer brain metastases (BCBrM) diverge based on the status of extracranial disease (ECD). An in-depth understanding of the impact of ECD on outcomes in HER2 + BCBrM has never been performed. Our study explores the implications of ECD status on intracranial progression-free survival (iPFS) and overall survival (OS) after first incidence of HER2 + BCBrM and radiation., Methods: A retrospective analysis was performed of 151 patients diagnosed with initial HER2 + BCBrM who received radiation therapy to the central nervous system (CNS) at Duke between 2008 and 2021. The primary endpoint was iPFS defined as the time from first CNS radiation treatment to intracranial progression or death. OS was defined as the time from first CNS radiation or first metastatic disease to death. Systemic staging scans within 30 days of initial BCBrM defined ECD status as progressive, stable/responding or none (isolated brain relapse)., Results: In this cohort, > 70% of patients had controlled ECD with either isolated brain relapse (27%) or stable/responding ECD (44%). OS from initial metastatic disease to death was markedly worse for patients with isolated intracranial relapse (median = 28.4 m) compared to those with progressive or stable/responding ECD (48.8 m and 71.5 m, respectively, p = 0.0028). OS from first CNS radiation to death was significantly worse for patients with progressive ECD (16.9 m) versus stable/responding (36.6 m) or isolated intracranial relapse (28.4 m, p = 0.007). iPFS did not differ statistically based on ECD status. Receipt of systemic therapy after first BCBrM significantly improved iPFS (HR 0.45, 95% CI: 0.25-0.81, p = 0.008) and OS (HR: 0.43 (95% CI: 0.23-0.81); p = 0.001)., Conclusion: OS in patients with HER2 + isolated BCBrM was inferior to those with concurrent progressive or stable/responding ECD. Studies investigating initiation of brain-penetrable HER2-targeted therapies earlier in the disease course of isolated HER2 + intracranial relapse patients are warranted., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Competing Interests: Naren RamakrishnaStock and Other Ownership Interests: Cytecare Cancer Center, Bangalore IndiaResearch Funding: Decimal (Inst) Carey K. AndersHonoraria: Eisai, Genentech/Roche, Ipsen, Seattle Genetics, Puma Biotechnology, AstraZeneca, Elucida Oncology, Immunomedics, AthenexConsulting or Advisory Role: Genentech/Roche, Puma Biotechnology, Eisai, Ipsen, Seattle Genetics, AstraZeneca, Elucida Oncology, ImmunomedicsResearch Funding: Puma Biotechnology (Inst), Lilly (Inst), Merck (Inst), Nektar (Inst), Tesaro (Inst), Seattle Genetics (Inst), G1 Therapeutics (Inst), Pfizer (Inst), ZION (Inst), Novartis Pharmaceuticals UK Ltd (Inst)Patents, Royalties, Other Intellectual Property: UpToDate.com, Jones and BartlettTravel, Accommodations, Expenses: EisaiNo other potential conflicts of interest were reported.

Opinion Statement: Brain metastasis arising from breast cancer is associated with a poor prognosis. Various systemic chemotherapy and targeted therapies which are effective against breast cancer often fail to provide benefits against brain metastasis. This is mainly due to limited penetration of the therapies across the blood-brain barrier, and divergent evolution of brain metastasis compared to the primary tumor. Thus, brain metastasis is typically treated upfront with local therapies, such as surgery and radiation, followed by systemic therapies. Systemic therapies with CNS permeability are favored in patients with brain metastasis. This paper reviews various systemic therapy options for breast cancer brain metastasis., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Purpose: To update evidence-based guideline recommendations to practicing oncologists and others on systemic therapy for patients with human epidermal growth factor receptor 2 (HER2)-positive advanced breast cancer., Methods: An Expert Panel conducted a targeted systematic literature review (for both systemic treatment and CNS metastases) and identified 545 articles. Outcomes of interest included efficacy and safety., Results: Of the 545 publications identified and reviewed, 14 were identified to form the evidentiary basis for the guideline recommendations., Recommendations: HER2-targeted therapy is recommended for patients with HER2-positive advanced breast cancer, except for those with clinical congestive heart failure or significantly compromised left ventricular ejection fraction, who should be evaluated on a case-by-case basis. Trastuzumab, pertuzumab, and taxane for first-line treatment and trastuzumab deruxtecan for second-line treatment are recommended. In the third-line setting, clinicians should offer other HER2-targeted therapy combinations. There is a lack of head-to-head trials; therefore, there is insufficient evidence to recommend one regimen over another. The patient and the clinician should discuss differences in treatment schedule, route, toxicities, etc during the decision-making process. Options include regimens with tucatinib, trastuzumab emtansine, trastuzumab deruxtecan (if either not previously administered), neratinib, lapatinib, chemotherapy, margetuximab, hormonal therapy, and abemaciclib plus trastuzumab plus fulvestrant, and may offer pertuzumab if the patient has not previously received it. Optimal duration of chemotherapy is at least 4-6 months or until maximum response, depending on toxicity and in the absence of progression. HER2-targeted therapy can continue until time of progression or unacceptable toxicities. For patients with HER2-positive and estrogen receptor-positive or progesterone receptor-positive breast cancer, clinicians may recommend either standard first-line therapy or, for selected patients, endocrine therapy plus HER2-targeted therapy or endocrine therapy alone.Additional information is available at www.asco.org/breast-cancer-guidelines.

Purpose: To provide updated evidence- and consensus-based guideline recommendations to practicing oncologists and others on the management of brain metastases for patients with human epidermal growth factor receptor 2 (HER2)-positive advanced breast cancer up to 2021., Methods: An Expert Panel conducted a targeted systematic literature review (for both systemic therapy for non-CNS metastases and for CNS metastases of HER2+ guideline updates) that identified 545 articles. Outcomes of interest included overall survival, progression-free survival, and adverse events., Results: Of the 545 publications identified and reviewed, six on systemic therapy were identified to form the evidentiary basis for the systemic therapy for CNS metastases guideline recommendations., Recommendations: Patients with brain metastases should receive appropriate local therapy and systemic therapy, if indicated. Local therapies include surgery, whole-brain radiotherapy, and stereotactic radiosurgery. Memantine and hippocampal avoidance should be added to whole-brain radiotherapy when possible. Treatments depend on factors such as patient prognosis, presence of symptoms, resectability, number and size of metastases, prior therapy, and whether metastases are diffuse. Other options include systemic therapy, best supportive care, enrollment onto a clinical trial, and/or palliative care. There are insufficient data to recommend for or against performing routine magnetic resonance imaging to screen for brain metastases; clinicians should have a low threshold for magnetic resonance imaging of the brain because of the high incidence of brain metastases among patients with HER2-positive advanced breast cancer.Additional information is available at www.asco.org/breast-cancer-guidelines.

Background: Triple negative breast cancer (TNBC) is an aggressive variant of breast cancer that lacks the expression of estrogen and progesterone receptors (ER and PR) and HER2. Nearly 50% of patients with advanced TNBC will develop brain metastases (BrM), commonly with progressive extracranial disease. Immunotherapy has shown promise in the treatment of advanced TNBC; however, the immune contexture of BrM remains largely unknown. We conducted a comprehensive analysis of TNBC BrM and matched primary tumors to characterize the genomic and immune landscape of TNBC BrM to inform the development of immunotherapy strategies in this aggressive disease., Methods: Whole-exome sequencing (WES) and RNA sequencing were conducted on formalin-fixed, paraffin-embedded samples of BrM and primary tumors of patients with clinical TNBC ( n = 25, n = 9 matched pairs) from the LCCC1419 biobank at UNC-Chapel Hill. Matched blood was analyzed by DNA sequencing as a comparison for tumor WES for the identification of somatic variants. A comprehensive genomics assessment, including mutational and copy number alteration analyses, neoantigen prediction, and transcriptomic analysis of the tumor immune microenvironment were performed., Results: Primary and BrM tissues were confirmed as TNBC (23/25 primaries, 16/17 BrM) by immunohistochemistry and of the basal intrinsic subtype (13/15 primaries and 16/19 BrM) by PAM50. Compared to primary tumors, BrM demonstrated a higher tumor mutational burden. TP53 was the most frequently mutated gene and was altered in 50% of the samples. Neoantigen prediction showed elevated cancer testis antigen- and endogenous retrovirus-derived MHC class I-binding peptides in both primary tumors and BrM and predicted that single-nucleotide variant (SNV)-derived peptides were significantly higher in BrM. BrM demonstrated a reduced immune gene signature expression, although a signature associated with fibroblast-associated wound healing was elevated in BrM. Metrics of T and B cell receptor diversity were also reduced in BrM., Conclusions: BrM harbored higher mutational burden and SNV-derived neoantigen expression along with reduced immune gene signature expression relative to primary TNBC. Immune signatures correlated with improved survival, including T cell signatures. Further research will expand these findings to other breast cancer subtypes in the same biobank. Exploration of immunomodulatory approaches including vaccine applications and immune checkpoint inhibition to enhance anti-tumor immunity in TNBC BrM is warranted., Competing Interests: JP is an inventor on patent applications for the Breast PAM50 assay. BV and JP report equity and consulting fees for GeneCentric Therapeutics. CA receives research funding from PUMA, Lilly, Merck, Seattle Genetics, Nektar, Tesaro, G1-Therapeutics, ZION, Novartis, and Pfizer; compensated consultant role: Genentech (1/2019-), Eisai (1/2019-), IPSEN (2/2019-), Seattle Genetics (11/15/2019-11/15/2020); Astra Zeneca (3/2020-6/2020), Novartis (5/2020-5/2022), Immunomedics (10/1/2020-9/22/2021), Elucida (9/2020); and royalties from UpToDate and Jones and Bartlett. LC has received institutional research funding from Syndax, Novartis, NanoString Technologies, AbbVie, Seattle Genetics, and Veracyte. An immediate family member has a royalty-sharing agreement and investorship interest in licensed IP to startup company Falcon Therapeutics that is designing neural stem-cell-based therapy for glioblastoma multiforme. She has uncompensated relationships with Sanofi, Novartis, G1 Therapeutics, Genentech/Roche, GlaxoSmithKline, AstraZeneca/Daiichi Sankyo, Aptitude Health, Exact Sciences and Eisai. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Routh, Van Swearingen, Sambade, Vensko, McClure, Woodcock, Chai, Cuaboy, Wheless, Garrett, Carey, Hoyle, Parker, Vincent and Anders.)

Importance: Patients with breast cancer and brain metastases (BM) have a poor prognosis and high clinical need for novel treatments; however, historically, studies have often excluded these patients. Although the BEACON study did not meet its primary end point, treatment with etirinotecan pegol vs chemotherapy of the physician's choice for patients with advanced breast cancer demonstrated a significant improvement in overall survival (OS) for the prespecified patient subgroup with preexisting, pretreated, and nonprogressive BM., Objective: To compare clinical outcomes in patients with BM treated with etirinotecan pegol vs chemotherapy of the physician's choice in a confirmatory trial., Design, Setting, and Participants: This study was a phase 3, open-label, randomized clinical trial (ATTAIN) in patients with metastatic breast cancer and a history of stable pretreated BM who experienced disease progression while receiving chemotherapy in the metastatic setting. The trial took place at 47 sites in 10 countries, and patients were enrolled between March 7, 2017, and November 6, 2019., Interventions: Patients were randomized to receive etirinotecan pegol, 145 mg/m2, every 21 days or chemotherapy (eribulin, ixabepilone, vinorelbine, gemcitabine, paclitaxel, docetaxel, or nab-paclitaxel)., Main Outcomes and Measures: The primary end point was OS. Key secondary end points included progression-free survival, objective response rate, duration of response, and the clinical benefit rate., Results: A total of 178 female patients (9 [5.1%] Asian, 8 [4.5%] Black or African American, and 123 [69.1] White individuals) were randomized to receive treatment with etirinotecan pegol (92 [51.7%]; median [range] age, 53 [27-79] years) or chemotherapy (86 [48.3%]; median [range] age, 52 [24-77] years). Median OS was similar in both groups (etirinotecan pegol, 7.8 months; chemotherapy, 7.5 months; hazard ratio [HR], 0.90; 95% CI, 0.61-1.33; P = .60). Median progression-free survival for non-central nervous system metastases per blinded independent central review for etirinotecan pegol vs chemotherapy was 2.8 and 1.9 months (HR, 0.72; 95% CI, 0.45-1.16; P = .18) and 3.9 vs 3.3 months, respectively, for central nervous system metastases (HR, 0.59; 95% CI, 0.33-1.05; P = .07). Safety profiles between the groups were largely comparable., Conclusions and Relevance: The results of the ATTAIN randomized clinical trial found no statistically significant difference in outcomes between treatment with etirinotecan pegol and chemotherapy in patients with BM. However, this study represents one of the largest published trials dedicated to patients with breast cancer and BM and may help to inform further research., Trial Registration: ClinicalTrials.gov Identifier: NCT02915744.