Unique genomic alterations in the circulating tumor DNA of patients with solid tumors brain metastases

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.

Triple Negative Breast Cancer and Brain Metastases

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.

National Cancer Institute Collaborative Workshop on Shaping the Landscape of Brain Metastases Research: challenges and recommended priorities

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.

Efficacy of a Dual-Epitope Dendritic Cell Vaccine as Part of Combined Immunotherapy for HER2-Expressing Breast Tumors

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.

The Enduring Effects of COVID for Cancer Care: Learning from Real-Life Clinical Practice

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.

Available Systemic Treatments and Emerging Therapies for Breast Cancer Brain Metastases

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.

Phase I Study and Cell-Free DNA Analysis of T-DM1 and Metronomic Temozolomide for Secondary Prevention of HER2-Positive Breast Cancer Brain Metastases

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.

Current drug development and trial designs in neuro-oncology: report from the first American Society of Clinical Oncology and Society for Neuro-Oncology Clinical Trials Conference

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.

Durable responses in patients with HER2+ breast cancer and leptomeningeal metastases treated with trastuzumab deruxtecan

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.

Cisplatin with veliparib or placebo in metastatic triple-negative breast cancer and BRCA mutation-associated breast cancer (S1416): a randomised, double-blind, placebo-controlled, phase 2 trial

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/m2, 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.

Preclinical and Clinical Efficacy of Trastuzumab Deruxtecan in Breast Cancer Brain Metastases

PURPOSE

Brain metastases can occur in up to 50% of patients with metastatic HER2-positive breast cancer. Because patients with active brain metastases were excluded from previous pivotal clinical trials, the central nervous system (CNS) activity of the antibody-drug conjugate trastuzumab deruxtecan (T-DXd) is not well characterized.

EXPERIMENTAL DESIGN

We studied how T-DXd affects growth and overall survival in orthotopic patient-derived xenografts (PDX) of HER2-positive and HER2-low breast cancer brain metastases (BCBM). Separately, we evaluated the effects of T-DXd in a retrospective cohort study of 17 patients with stable or active brain metastases.

RESULTS

T-DXd inhibited tumor growth and prolonged survival in orthotopic PDX models of HER2-positive (IHC 3+) and HER2-low (IHC 2+/FISH ratio < 2) BCBMs. T-DXd reduced tumor size and prolonged survival in a T-DM1-resistant HER2-positive BCBM PDX model. In a retrospective multi-institutional cohort study of 17 patients with predominantly HER2-positive BCBMs, the CNS objective response rate (ORR) was 73% (11/15) while extracranial response rate was 45% (5/11). In the subset of patients with untreated or progressive BCBM at baseline, the CNS ORR was 70% (7/10). The median time on treatment with T-DXd was 8.9 (1.3-16.2) months, with 42% (7/17) remaining on treatment at data cutoff.

CONCLUSIONS

T-DXd demonstrates evidence of CNS activity in HER2-positive and HER2-low PDX models of BCBM and preliminary evidence of clinical efficacy in a multi-institution case series of patients with BCBM. Prospective clinical trials to further evaluate CNS activity of T-DXd in patients with active brain metastases are warranted. See related commentary by Soffietti and Pellerino, p. 8.

Brain metastasis as the first and only metastatic relapse site portends worse survival in patients with advanced HER2 + breast cancer

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.

Systemic Therapy Approaches for Breast Cancer Brain and Leptomeningeal Metastases

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.

Comprehensive Analysis of the Immunogenomics of Triple-Negative Breast Cancer Brain Metastases From LCCC1419

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.

Brain metastasis as first and only metastatic relapse site portends poor outcomes in patients with advanced HER2+ breast cancer

1045

Background: In patients (pts) with stable or no extracranial disease (ECD) presenting with breast cancer brain metastases (BCBrMs), current guidelines recommend pts receive local therapy with radiation +/- surgery, without changing systemic therapy. However, preliminary studies suggest that pts with isolated HER2+ BCBrM without ECD have inferior overall survival (OS) compared to pts with concurrent ECD. Our study further explores the implications of ECD status on intracranial progression free survival (iPFS) and OS. Methods: Retrospective analysis was performed on data from 153 pts diagnosed with initial HER2+ BCBrM who received CNS radiation at Duke between 2008 and 2020. Demographics, dates of metastatic and BCBrM diagnosis, ECD status at first CNS event, systemic therapy, and outcomes were collected. The primary endpoint was iPFS defined as the time from first CNS radiation to the subsequent documentation of intracranial progression (RANO-BM). OS was defined as time from first CNS radiation and first metastatic disease to date of death or last known contact. ECD status was defined by RECIST1.1 from systemic staging scans within 30 days of first CNS event. Results: In this cohort of 153 pts with HER2+ BCBrMs undergoing CNS radiation, > 70% of pts with known ECD status had controlled systemic disease: either no ECD (27%) or stable/responding disease (44%). 64% of pts’ tumors were ER+. Median age was 50 years (range 24 – 75). Most pts (59%) developed first CNS event during adjuvant or 1st/2nd line metastatic therapy. CNS radiation treatment included 48% of pts receiving SRS only, 9% WBRT only, and 43% SRS and WBRT. All pts with no ECD presented with isolated BCBrMs as first metastatic disease. Among pts with known ECD status, OS from initial metastatic disease to death was markedly worse for pts with isolated brain metastases or no ECD (median = 28.4m, 95% CI: 18.1 to not reached) compared to those with progressive or stable/responding ECD (48.8m, 95% CI: 40.5 to 65.0; and 68.1m, 95% CI: 55.2 to 85.7, respectively; log-rank p = 0.004). OS from first CNS involvement to death was significantly worse for pts with progressive ECD (17.8m, 95% CI: 13.7 to 28.8) versus stable/responding (36.6m, 95% CI: 29.7 to 45.2) or no ECD (28.4m, 95% CI: 18.1 to not reached; log-rank p = 0.008). iPFS did not differ statistically among subgroups of pts with known ECD status: progressive ECD (median = 7.7m), no ECD (8.3m), or stable/responding ECD (11.2m) (log-rank p = 0.15). Conclusions: Overall survival in pts with HER2+ isolated BCBrM was markedly inferior to that of pts with progressive or stable/responding ECD. Studies investigating initiation of brain penetrable HER2-targeted therapies earlier in the disease course of isolated HER2+ BCBrMs pts are warranted.

Dose-finding and -expansion studies of trastuzumab deruxtecan in combination with other anti-cancer agents in patients (pts) with advanced/metastatic HER2+ (DESTINY-Breast07 [DB-07]) and HER2-low (DESTINY-Breast08 [DB-08]) breast cancer (BC)

3025

Background: Trastuzumab deruxtecan (T-DXd), an antibody-drug conjugate composed of a humanized anti-HER2 monoclonal antibody and a topoisomerase I inhibitor payload, is approved for pts with unresectable or metastatic HER2+ BC with ≥2 prior anti-HER2–based therapies. T-DXd showed improved progression-free survival vs trastuzumab emtansine (T-DM1) as an earlier-line treatment (tx) for pts with HER2+ metastatic BC in the phase 3 DESTINY-Breast03 trial (Cortes J, et al. Ann Oncol. 2021;32:S1283-S1346. Abstract LBA1). Preliminary antitumor activity of T-DXd was shown in heavily pretreated pts with HER2-low advanced/metastatic BC in the phase 1 DS8201-A-J101 trial (Modi S, et al. J Clin Oncol. 2020;38:1887-1896). We report preliminary results from the dose-finding phase of 2 trials investigating T-DXd combination tx in HER2+ or HER2-low metastatic BC. Methods: DB-07 (phase 1b/2; NCT04538742) and DB-08 (phase 1b; NCT04556773) are 2-part, modular, open-label, multicenter trials of T-DXd combined with other anticancer tx in pts with advanced/metastatic BC that is HER2+ (DB-07) or HER2 low (DB-08). Part 1 of each study is an ongoing dose-finding phase; pts must have ≥1 prior tx for metastatic BC. Part 2 of each study is a dose-expansion phase; pts must have no (DB-07) or ≤1 (DB-08) prior tx for metastatic BC. We report preliminary results from the T-DXd + pertuzumab module of DB-07 part 1 (data cutoff: Oct 15, 2021) and T-DXd + anastrozole and T-DXd + fulvestrant modules of DB-08 part 1 (data cutoff: Sep 27, 2021); pts in the DB-08 modules must be hormone receptor positive. The part 1 primary objective was to assess safety and tolerability and determine the recommended phase 2 dose (RP2D) according to the modified toxicity probability interval-2 algorithm. Pts were followed up beyond the 21-day dose-limiting toxicity (DLT) period (28 days for T-DXd + fulvestrant) for safety events. Results: In DB-07, 7 pts were enrolled and received T-DXd 5.4 mg/kg + pertuzumab 420 mg (loading dose: 840 mg) every 3 wk (q3w; not evaluable for DLTs, n = 1). In DB-08, 6 pts were enrolled and received T-DXd 5.4 mg/kg q3w + anastrozole 1 mg daily (not evaluable for DLTs, n = 1); another 6 pts were enrolled and received T-DXd 5.4 mg/kg q3w + fulvestrant 500 mg every 4 wk (loading dose: 500 mg cycle 1 days 1 and 15). For all 3 modules, no DLTs were reported in any DLT-evaluable pts; the dose levels used in part 1 were approved to be the RP2Ds for use in the dose-expansion part of each corresponding module. No deaths on study or cases of interstitial lung disease/pneumonitis were reported to date. Conclusions: The RP2Ds for the T-DXd combinations were the standard doses for BC of each individual drug. These studies are ongoing, with additional T-DXd combinations being evaluated and further follow-up underway. Clinical trial information: NCT04538742; NCT04556773.

Systemic Therapy for Advanced Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer: ASCO Guideline Update

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.

Management of Advanced Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer and Brain Metastases: ASCO Guideline Update

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.

Systemic Therapy Type and Timing Effects on Radiation Necrosis Risk in HER2+ Breast Cancer Brain Metastases Patients Treated With Stereotactic Radiosurgery

Background

There is a concern that HER2-directed systemic therapies, when administered concurrently with stereotactic radiosurgery (SRS), may increase the risk of radiation necrosis (RN). This study explores the impact of timing and type of systemic therapies on the development of RN in patients treated with SRS for HER2+ breast cancer brain metastasis (BCBrM).

Methods

This was a single-institution, retrospective study including patients >18 years of age with HER2+ BCBrM who received SRS between 2013 and 2018 and with at least 12-month post-SRS follow-up. Presence of RN was determined via imaging at one-year post-SRS, with confirmation by biopsy in some patients. Demographics, radiotherapy parameters, and timing (“during” defined as four weeks pre- to four weeks post-SRS) and type of systemic therapy (e.g., chemotherapy, HER2-directed) were evaluated.

Results

Among 46 patients with HER2+ BCBrM who received SRS, 28 (60.9%) developed RN and 18 (39.1%) did not based on imaging criteria. Of the 11 patients who underwent biopsy, 10/10 (100%) who were diagnosed with RN on imaging were confirmed to be RN positive on biopsy and 1/1 (100%) who was not diagnosed with RN was confirmed to be RN negative on biopsy. Age (mean 53.3 vs 50.4 years, respectively), radiotherapy parameters (including total dose, fractionation, CTV and size target volume, all p>0.05), and receipt of any type of systemic therapy during SRS (60.7% vs 55.6%, p=0.97) did not differ between patients who did or did not develop RN. However, there was a trend for patients who developed RN to have received more than one agent of HER2-directed therapy independent of SRS timing compared to those who did not develop RN (75.0% vs 44.4%, p=0.08). Moreover, a significantly higher proportion of those who developed RN received more than one agent of HER2-directed therapy during SRS treatment compared to those who did not develop RN (35.7% vs 5.6%, p=0.047).

Conclusions

Patients with HER2 BCBrM who receive multiple HER2-directed therapies during SRS for BCBrM may be at higher risk of RN. Collectively, these data suggest that, in the eight-week window around SRS administration, if HER2-directed therapy is medically necessary, it is preferable that patients receive a single agent.

Treatment With Etirinotecan Pegol for Patients With Metastatic Breast Cancer and Brain Metastases: Final Results From the Phase 3 ATTAIN Randomized Clinical Trial

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.

Systemic management of brain metastases in HER2+ breast cancer in 2022

Up to half of all patients with metastatic human epidermal growth factor receptor 2-positive (HER2+) breast cancer will eventually acquire brain metastases (BrMs), which are associated with reduced overall survival and decreased quality of life. Although the median overall survival was previously less than a year, novel systemic treatments have significantly extended life expectancy in patients with HER2+ breast cancer BrMs. The current first-line standard of care for all patients with HER2+ metastatic breast cancer, regardless of BrMs status, is dual HER2 antibody therapy with pertuzumab/trastuzumab plus a taxane. Second-line systemic therapy has recently evolved, with the option of trastuzumab deruxtecan (T-DXd) or tucatinib in combination with trastuzumab and capecitabine. T-DXd has shown dramatically superior progression-free survival in comparison with trastuzumab emtansine (T-DM1) in patients with stable BrMs in the second-line setting. Patients who have untreated or locally treated/progressive BrMs may benefit from a regimen with robust intracranial response rates, such as tucatinib in combination with trastuzumab and capecitabine. Third-line therapy and beyond includes multiple options that require careful selection, with the patient's BrMs status, comorbidities, and performance status taken into account. In this review, we focus on current management and evolving strategies for the treatment of patients with HER2+ breast cancer BrMs.

Abstract PD6-06: Comprehensive characterization of neurotransmitters and neuronal signaling gene alterations in invasive breast cancers

BACKGROUNDIt has been reported that the sympathetic nervous system and associated neurotransmitters (NTs) play a pivotal role in driving breast cancer (BC) tumorigenesis and metastasis, however, comprehensive characterization of these pathways in BC is lacking. The purpose of this study was to retrospectively characterize NTs and neuronal signaling (NTNS) gene alterations in a large real-world BC cohort. METHODS A total of 6464 BC tumors were analyzed by next generation sequencing (NextSeq, 592 genes and WES, NovaSEQ, 720 genes) and whole transcriptome sequencing (WTS, NovaSeq) at Caris Life Sciences. Gene set variation analysis (GSVA) scores were calculated (positive: higher gene expressions in a selected gene set compared to genes outside that gene set in each tumor specimen, vice versa for negative) to assess expression of major NTNS genes, including GABA, nicotinic (NIC), muscarinic (MUS), dopamine (DA), reelin (RELN), and glial cell line-derived neurotrophic factor (GDNF). GSVA scores were compared by histologic subtype, primary or metastatic site, and hormone receptor (HR) and HER2 status with corrected Wilcoxon-Mann-Whitney testing. All significance levels were p&lt;0.01. RESULTS The 6464 BC specimens in this cohort included 2520 primary sites and 3944 metastasis (mets) (liver: 1012; lymph node: 714; bone: 575; lung: 420; brain: 196). Predictive biomarker status in this cohort was HR+/HER2-: 3705; HR+/HER2+: 238; HR-/HER2+: 189; TNBC: 1654. Invasive ductal carcinomas (IDC) were the most common histologic subtype and demonstrated significantly higher GSVA scores for RELN and NIC pathways with respect to invasive lobular carcinomas (ILC) (Table). TNBC tumors had significantly higher enrichment overall (GABA, -0.04 vs -0.14; RELN, -0.05 vs -0.31; DA, -0.03 vs -0.08; MUS, 0.13 vs -0.16; NIC, 0.01 vs -0.12; and GDNF, 0.04 vs -0.04). HR-/HER2+ had significantly higher scores in GABA, -0.04 vs -0.14; RELN, -0.03 vs -0.31; MUS, 0.12 vs -0.16; and NIC, -0.01 vs -0.12 genes. Brain mets had significantly enriched pathway scores for GABA, 0.30 vs -0.13; MUS, 0.15 vs -0.08; and NIC, 0.13 vs -0.09 compared to primary tumors. Similarly, GABA,0.09 vs -0.13; DA, 0.07 vs -0.05; MUS, 0.17 vs -0.08; and NIC, 0.02 vs -0.09 pathways were enriched in bone mets compared to those from primary tumors. CONCLUSION Our results demonstrate that NTNS pathways are significantly enriched in IDC, TNBC tumors, and particularly in brain and bone mets. Our data advance the current understanding of the role of NTNS pathways in BC tumorigenesis and metastasis. Further investigation on genetic. determinants and signaling alternations associated with the observed NTNS pathway deregulation is warranted and could inform the development of novel therapeutic strategies. Significant comparisons with Bonferroni corrected p values are shown with an asterisk.

Citation Format: Irene Kang, Krutika Deshpande, Sarah Persing, Jun Yin, Joanne Xiu, Wolfgang Michael Korn, Jia Zeng, Evanthia T Roussos-Torres, Janice Lu, Darcy Spicer, Stephen F Sener, Antoinette R Tan, Ashley Sumrall, David SB Hoon, Cynthia X Ma, Carey K Anders, Heather L McArthur, Reva Basho, Heinz-Josef Lenz, Josh Neman. Comprehensive characterization of neurotransmitters and neuronal signaling gene alterations in invasive breast cancers [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD6-06.

Abstract P1-21-06: Phase I study of T-DM1 and metronomic temozolomide in secondary prevention of HER2+ breast cancer brain metastases following local radiation therapy

Background: The incidence of breast cancer brain metastases is rising, and, these lesions in the central nervous system (CNS) and their treatments cause physical and neurocognitive impairment. Only modest incremental advances in progression free survival have been achieved with drugs to treat CNS lesions, while nearly half of the patients who receive SRS will develop new brain metastases within 1 year. In murine models of breast cancer, we demonstrated that low doses of temozolomide (TMZ) administered in a prophylactic, metronomic fashion significantly prevented development of brain metastases. No effect, however, was seen in established brain metastases or systemic breast cancer metastases. We hypothesize that low dose, metronomic TMZ will prevent the outgrowth of brain lesions in HER2+ patients, when added to an active anti-HER2 treatment. We present here the results of the phase I trial combining T-DM1 to TMZ for the prevention of additional brain metastases after their first occurrence and local treatment. Methods: Eligible patients had HER2+ breast cancer with brain metastases and were within 12 weeks of local brain metastases therapy (WBRT, SRS and or surgery), with PS 0-2 and adequate end organ function. Standard doses of T-DM1 were administered IV every 21 days (3.6 mg/kg) and TMZ was given PO daily in a 3+3 design at 30, 40 or 50 mg/m2, continuously. The DLT period was one 21d cycle. Safety was assessed by CTCAEv4.0 and response by RECISTv1.1 and RANO-BM. Brain MRI and systemic CT scans were performed every 6 weeks. Blood samples for correlatives evaluation were collected at baseline and every cycle while on trial. CSF was collected at baseline and C3D1 for all patients. Questionnaires (MDASI-BT and PROMIS®) for evaluation of symptoms and quality of life were completed every 6 weeks. Results: Twelve women with median age 55.5yr (44-67) were enrolled. Only 3 (25%) patients had HR+/HER2+ tumors at initial diagnosis. Nine (75%) patients presented stages II and III disease at initial diagnosis, and developed brain metastases at the diagnosis of first recurrence. Nine (75%) patients received SRS therapy and 3 (25%) received WBRT prior to trial enrollment. Grade 3 or 4 AEs included thrombocytopenia (1/12), neutropenia (1/12), lymphopenia (6/12) and decreased CD4 (6/12), requiring pentamidine for PCP prophylaxis. No DLT was observed. Four patients underwent dose reductions (thrombocytopenia, fatigue and peripheral neuropathy), all of them enrolled on the highest TMZ dose. Median follow-up on study is now 9.6m (1.2-32) and no patient developed new parenchymal brain metastases. Five patients remain on study, while 7 are off study due to progression at previously irradiated CNS lesion (2), progression of systemic disease (2), focal leptomeningeal involvement (1), new cancer (1) and persistent thrombocytopenia (1). Completion rates for the questionnaires were 99% by Cycle 15 (81 completed out of expected 82) and 90% by Cycle 41 (123/137), and will be reported at presentation. Conclusion: Metronomic TMZ in combination with standard dose T-DM1 is tolerable and shows promising activity in secondary prevention of HER2+ brain metastases. Systematic longitudinal symptom assessments in breast cancer patients with brain metastasis are feasible. A randomized phase II expansion of this trial with T-DM1 or T-Dxd +/- TMZ is planned.

Citation Format: Alexandra S Zimmer, Seth Steinberg, Mark Gilbert, Terri Armstrong, Eric Burton, Nicole Houston, Dee Dee Smart, Nadia Biassou, John Butman, Priscilla K Brastianos, Carey K Anders, Stanley Lipkowitz, Patricia S Steeg. Phase I study of T-DM1 and metronomic temozolomide in secondary prevention of HER2+ breast cancer brain metastases following local radiation therapy [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-21-06.

Evaluating the efficacy of a priming dose of cyclophosphamide prior to pembrolizumab to treat metastatic triple negative breast cancer

PURPOSE

Triple negative breast cancer (TNBC) is characterized by the presence of immune cells in the tumor microenvironment, however, the response to single-agent immune checkpoint inhibitor (ICI) therapy is modest. Preclinical models have demonstrated that intratumoral regulatory T cells (T_regs) dampen the antitumor response to ICI. We performed a single-arm phase II trial to evaluate the efficacy of a single low dose of cyclophosphamide (Cy) to deplete T_regs administered before initiating pembrolizumab.

PATIENTS AND METHODS

40 patients with pretreated metastatic TNBC were enrolled. The primary endpoints were progression-free survival (PFS) and change in peripheral blood T_regs after Cy. Secondary endpoints included overall response rate (ORR), duration of response, overall survival, treatment-related adverse events (AEs), and correlative evaluations.

RESULTS

Median PFS was 1.8 months, and the ORR was 21%. T_regs were not significantly decreased after Cy prior to ICI (-3.3%, p=0.19), and increased significantly after the first cycle of therapy (+21% between cycles 1 and 2, p=0.005). Immune-related AEs were similar to historical pembrolizumab monotherapy, and were associated with response to therapy (p=0.02). Patients with pretreatment tumors harboring increased expression of B cell metagene signatures and increased circulating B cell receptor repertoire diversity were associated with clinical response and immune-related toxicity (IRT).

CONCLUSIONS

Among patients with heavily pretreated TNBC, Cy prior to pembrolizumab did not significantly deplete T_regs, and in those with decreased numbers there was rapid recovery following therapy. Increased B cell gene expression in baseline samples was associated with clinical response and IRT.

A Need for More Molecular Profiling in Brain Metastases

As local disease control improves, the public health impact of brain metastases (BrM) continues to grow. Molecular features are frequently different between primary and metastatic tumors as a result of clonal evolution during neoplasm migration, selective pressures imposed by systemic treatments, and differences in the local microenvironment. However, biomarker information in BrM is not routinely obtained despite emerging evidence of its clinical value. We review evidence of discordance in clinically actionable biomarkers between primary tumors, extracranial metastases, and BrM. Although BrM biopsy/resection imposes clinical risks, these risks must be weighed against the potential benefits of assessing biomarkers in BrM. First, new treatment targets unique to a patient's BrM may be identified. Second, as BrM may occur late in a patient's disease course, resistance to initial targeted therapies and/or loss of previously identified biomarkers can occur by the time of occult BrM, rendering initial and other targeted therapies ineffective. Thus, current biomarker data can inform real-time treatment options. Third, biomarker information in BrM may provide useful prognostic information for patients. Appreciating the importance of biomarker analyses in BrM tissue, including how it may identify specific drivers of BrM, is critical for the development of more effective treatment strategies to improve outcomes for this growing patient population.

Advances in the management of breast cancer brain metastases

The development of breast cancer (BC) brain metastases (BrM) is a common complication of advanced disease, occurring in up to half of the patients with advanced disease depending on the subtype. The management of BCBrM requires complex multidisciplinary care including local therapy, surgical resection and/or radiotherapy, palliative care, and carefully selected systemic therapies. Significant progress has been made in the human epidermal growth factor receptor 2-positive (HER2+) BCBrM population due to novel brain penetrable systemic therapies. Increased inclusion of patients with BCBrM in clinical trials using brain-penetrant systemic therapies recently led to the first FDA approval of a HER2-directed therapy specifically in the BCBrM population in the last year. Advances for the treatment of HR+/HER2- and TNBC BCBrM subgroups continue to evolve. In this review, we will discuss the diagnosis and multidisciplinary care of BCBrM. We focus on recent advances in neurosurgery, radiation therapy, and systemic treatment therapies with intracranial activity. We also provide an overview of the current clinical trial landscape for patients with BCBrM.

Cytotoxic Engineered Induced Neural Stem Cells as an Intravenous Therapy for Primary Non-Small Cell Lung Cancer and Triple-Negative Breast Cancer

Converting human fibroblasts into personalized induced neural stem cells (hiNSC) that actively seek out tumors and deliver cytotoxic agents is a promising approach for treating cancer. Herein, we provide the first evidence that intravenously-infused hiNSCs secreting cytotoxic agent home to and suppress the growth of non-small cell lung cancer (NSCLC) and triple-negative breast cancer (TNBC). Migration of hiNSCs to NSCLC and TNBC in vitro was investigated using time-lapse motion analysis, which showed directional movement of hiNSCs to both tumor cell lines. In vivo, migration of intravenous hiNSCs to orthotopic NSCLC or TNBC tumors was determined using bioluminescent imaging (BLI) and immunofluorescent post-mortem tissue analysis, which indicated that hiNSCs colocalized with tumors within 3 days of intravenous administration and persisted through 14 days. In vitro, efficacy of hiNSCs releasing cytotoxic TRAIL (hiNSC-TRAIL) was monitored using kinetic imaging of co-cultures, in which hiNSC-TRAIL therapy induced rapid killing of both NSCLC and TNBC. Efficacy was determined in vivo by infusing hiNSC-TRAIL or control cells intravenously into mice bearing orthotopic NSCLC or TNBC and tracking changes in tumor volume using BLI. Mice treated with intravenous hiNSC-TRAIL showed a 70% or 72% reduction in NSCLC or TNBC tumor volume compared with controls within 14 or 21 days, respectively. Safety was assessed by hematology, blood chemistry, and histology, and no significant changes in these safety parameters was observed through 28 days. These results indicate that intravenous hiNSCs-TRAIL seek out and kill NSCLC and TNBC tumors, suggesting a potential new strategy for treating aggressive peripheral cancers.

OTHR-10. Diverse survival outcomes of HER2+ Breast Cancer Brain Metastases (BrCBM) presenting with isolated brain relapse compared to those with concurrent extracranial disease

Background

In patients with isolated HER2+ BrCBM and no extracranial disease (ECD), there are no consensus guidelines on optimal treatment approaches following CNS-directed therapy. Our goal was to determine the implications of ECD at time of first HER2+ BrCBM on intracranial progression-free survival (PFS1) and overall survival (OS).

Methods

Retrospective analysis was performed on 77 patients with HER2+ BrCBM who received 1^st CNS radiation from 2006–2020. Demographics, dates of metastatic and intracranial diagnosis, ECD status at 1st BrCBM, and outcomes were collected. The primary endpoint was PFS1 defined as time from first CNS radiation to the subsequent documentation of intracranial progression (RANO-BM). OS was defined as time from 1^st CNS radiation and 1^st metastatic disease to date of death/last known alive. ECD status was defined by RECIST1.1 from staging scans within 30 days of 1^st BrCBM.

Results

In this patient cohort, 25% (19/77) had isolated brain relapse/no ECD. Median age was 50 years. Most patients (58%) developed first BrCBM during adjuvant or early-line metastatic therapy. All patients with no ECD presented with isolated brain relapse as first metastatic presentation. Patients with concurrent ECD presented with first BrCBM at a median of 16.6m (95% CI: 10.5 to 25.3) after initial metastatic presentation. Median OS from initial metastatic presentation to death was worse for patients with isolated brain relapse (25.3m, 95% CI: 16.8 to 35.3) compared to those with concurrent ECD (49.7m, 95% CI: 43.2 to 62; p=0.01). Median OS from first CNS involvement to death was not statistically different amongst groups.

Conclusions

Patients with isolated HER2+ BrCBM as their initial metastatic event have substantially worse OS compared to patients with concurrent ECD developing CNS metastases later in their disease course. This population with isolated brain relapse deserves investigation of novel treatment algorithms, including earlier introduction of brain-penetrable HER2-targeted agents.

OTHR-14. An immunogenomic analysis of melanoma brain metastases (MBM) compared to extracranial metastases (ECM)

Background

MBM have a unique molecular profile compared to ECM.

Methods

We analyzed a previously published dataset from MD Anderson Cancer Center, including RNA-seq on surgically resected, FFPE MBM and ECM from the same patients. STAR pipeline was used to estimate mRNA abundance. DESeq2 package was used to perform differential gene expression (DGE) analyses. Pathway analysis was performed using Gene Set Enrichment Analysis (GSEA). Paired DGE and GSEA compared MBM vs. lymph node (LN) metastases (n = 16) and MBM vs. skin mets (n = 10). CIBERSORTx estimated relative abundance of immune cell types in MBM and ECM. GATK Mutect2 pipeline was used to call somatic mutations using paired normal tumor samples. Mutations were annotated using the Ensembl Variant Effect Predictor and visualized using the Maftools package in R.

RNA-seq was available on 54 human primary cutaneous melanomas (CM). Gene Ontology or KEGG Pathway analysis was performed using goana function of limma package in R.

Results

Paired GSEA found that autophagy pathways may be up-regulated in MBM vs. LN and MBM vs. skin mets. On a single-gene level, the most strongly up-regulated genes in autophagy pathways were GFAP and HBB. Fold changes in other autophagy-related genes were low and did not reach significance. Comparison between CM which recurred in brain vs. CM which did not recur identified up-regulation of autophagy pathways. CIBERSORTx identified an increased proportion of immune suppressive M2 macrophages compared to tumor suppressive M1 macrophages in MBMs and ECMs.

Conclusion

Up-regulation of autophagy pathways was observed in patient-matched MBM vs. LN and skin mets. This finding was driven by up-regulation of GFAP and HBB, which could reflect changes in the tumor microenvironment. Higher M2:M1 ratio may contribute to an immune suppressive tumor microenvironment and may be targetable. Validation of our findings in an independent Duke dataset is ongoing.

Physical Activity, Weight, and Outcomes in Patients Receiving Chemotherapy for Metastatic Breast Cancer (C40502/Alliance)

Background

Obesity and inactivity are associated with increased risk of cancer-related and overall mortality in breast cancer, but there are few data in metastatic disease.

Methods

Cancer and Leukemia Group B 40502 was a randomized trial of first-line taxane-based chemotherapy for patients with metastatic breast cancer. Height and weight were collected at enrollment. After 299 patients enrolled, the study was amended to assess recreational physical activity (PA) at enrollment using the Nurses' Health Study Exercise Questionnaire. Associations with progression-free survival (PFS) and overall survival (OS) were evaluated using stratified Cox modeling (strata included hormone receptor status, prior taxane, bevacizumab use, and treatment arm). All statistical tests were 2-sided.

Results

A total of 799 patients were enrolled, and at the time of data lock, median follow-up was 60 months. At enrollment, median age was 56.7 years, 73.1% of participants had hormone receptor-positive cancers, 42.6% had obesity, and 47.6% engaged in less than 3 metabolic equivalents of task (MET) hours of PA per week (<1 hour of moderate PA). Neither baseline body mass index nor PA was statistically significantly associated with PFS or OS, although there was a marginally statistically significant increase in PFS (hazard ratio = 0.83, 95% confidence interval = 0.79 to 1.02; P = .08) and OS (hazard ratio = 0.81, 95% confidence interval = 0.65 to 1.02; P = .07) in patients who reported PA greater than 9 MET hours per week vs 0-9 MET hours per week.

Conclusions

In a trial of first-line chemotherapy for metastatic breast cancer, rates of obesity and inactivity were high. There was no statistically significant relationship between body mass index and outcomes. More information is needed regarding the relationship between PA and outcomes.

Development of next-generation tumor-homing induced neural stem cells to enhance treatment of metastatic cancers

Engineered tumor-homing neural stem cells (NSCs) have shown promise in treating cancer. Recently, we transdifferentiated skin fibroblasts into human-induced NSCs (hiNSC) as personalized NSC drug carriers. Here, using a SOX2 and spheroidal culture-based reprogramming strategy, we generated a new hiNSC variant, hiNeuroS, that was genetically distinct from fibroblasts and first-generation hiNSCs and had significantly enhanced tumor-homing and antitumor properties. In vitro, hiNeuroSs demonstrated superior migration to human triple-negative breast cancer (TNBC) cells and in vivo rapidly homed to TNBC tumor foci following intracerebroventricular (ICV) infusion. In TNBC parenchymal metastasis models, ICV infusion of hiNeuroSs secreting the proapoptotic agent TRAIL (hiNeuroS-TRAIL) significantly reduced tumor burden and extended median survival. In models of TNBC leptomeningeal carcinomatosis, ICV dosing of hiNeuroS-TRAIL therapy significantly delayed the onset of tumor formation and extended survival when administered as a prophylactic treatment, as well as reduced tumor volume while prolonging survival when delivered as established tumor therapy.

Impact of extracranial disease status on survival after initial central nervous system (CNS) involvement and radiation therapy in HER2+ breast cancer brain metastases (BCBM)

1041

Background: BCBMs are very common in metastatic HER2+ breast cancer. CNS-directed local therapy is the gold standard for treatment, followed by systemic HER2-targeted therapies. In patients with HER2+ BCBM and stable extracranial disease (ECD), consensus guidelines recommend continuing current systemic therapy after local therapy. Our goal was to determine the implications of ECD status at time of HER2+ BCBM first CNS involvement on outcomes including intracranial progression-free survival (PFS1) and overall survival (OS). Methods: Retrospective analysis was performed on data extracted from 77 patients with HER2+ BCBM who received CNS radiation at Duke between 2006 and 2020 following initial documentation of CNS involvement. Demographics, dates of metastatic and intracranial diagnosis, ECD status at first CNS involvement, systemic therapy, and outcomes were collected. The primary endpoint was PFS1 defined as the time from first CNS radiation to the subsequent documentation of intracranial progression (RANO-BM). OS was defined as time from first CNS radiation and first metastatic disease to date of death or last known alive. ECD status was defined by RECIST1.1 from systemic staging scans within 30 days of first CNS involvement. Results: In this patient cohort of HER2+ BCBMs undergoing CNS radiation at first CNS involvement, >50% of patients had extracranial disease control: no ECD (25%) or stable/responding disease (31%). 52% of patients’ tumors were ER+. Median age was 50 years (range 27 – 75). Most patients (58%) developed first CNS involvement during adjuvant or first/second line metastatic therapy. For first CNS radiation, 49% received SRS and 48% WBRT. All patients with no ECD presented with isolated CNS disease as first metastatic presentation. Median OS in this cohort from initial metastatic disease to death was markedly worse for patients with no ECD (25.3m, 95% CI: 16.8 to 35.3) compared to those with progressive or stable/responding ECD (48.8m, 95% CI: 28.1 to 65; and 52.9 months, 95% CI: 43.7 to 73.3, respectively; p=0.03). Median OS from first CNS involvement to death was not statistically different amongst groups. This analysis did not detect median PFS1 differences based on ECD after first CNS radiation: progressive ECD (6.3m), no ECD (8.7m), or stable/responding ECD (10.6m) (p=0.13), though clinically meaningful differences were observed. Conclusions: Patients with isolated HER2+ BCBM with no ECD at the time of their initial CNS involvement (25% of population) have substantially worse OS compared to patients who present with ECD and develop CNS metastases later in their disease course. This population with isolated CNS disease at metastatic presentation deserves investigation of novel treatment algorithms, including earlier introduction of brain penetrable HER2-targeted agents.

An immunogenomic analysis of melanoma brain metastases (MBM) compared to extracranial metastases (ECM)

9521

Background: Previous work has shown that MBM have a unique molecular profile compared to ECM. Description of the biology of MBM will facilitate the design of rational therapies for patients (pts) with MBM. Methods: We analyzed a previously published dataset from MD Anderson Cancer Center, which includes RNA-seq on surgically resected FFPE MBM (88 tumors from 74 pts) and surgically resected ECM from the same pts (50 from 34 pts). WES on 18 matched pairs of MBM and ECM was available. The STAR pipeline was used to estimate mRNA abundance. The DESeq2 package was used to perform differential gene expression (DGE) analyses. Pathway analysis was performed using Gene Set Enrichment Analysis (GSEA). Paired DGE and GSEA analyses comparing MBM vs. lymph node metastases (LN mets, n = 16) and MBM vs. skin mets (n = 10) were performed. CIBERSORT estimated relative abundance of immune cell types in MBM and ECM. The GATK Mutect2 pipeline was used to call somatic mutations using paired normal tumor samples. Mutations were annotated using the Ensembl Variant Effect Predictor and visualized using the Maftools package in R. RNA-seq was available on 54 primary cutaneous melanoma (CM) pt samples, including 19 CM which did not recur, 19 CM which recurred as MBM, and 16 CM which recurred as ECM. Gene Ontology or KEGG Pathway analysis was performed using goana function of limma package in R. Results: Comparing MBM vs. LN and MBM vs. skin mets, paired DGE identified 136 and 89 up-regulated genes with a fold change > 2 and false-discovery rate (FDR) q-value < 0.05. Moreover, 308 and 659 down-regulated genes with a fold change < 0.5 were identified in MBM vs. LN and MBM vs. skin mets, respectively (q < 0.05). Paired GSEA found that autophagy signaling pathways may be up-regulated in MBM vs. LN and MBM vs. skin mets. On a single-gene level, comparing both MBM vs. LN and skin mets, the most strongly up-regulated genes in autophagy pathways were GFAP and HBB, whereas fold changes in the majority of other autophagy-related genes were low and did not reach significance. Comparison between CM which recurred in brain vs. CM which did not recur identified up-regulation of autophagy pathways. No difference in autophagy pathway expression was observed comparing between CM with any recurrence vs. without recurrence. CIBERSORT identified an increased proportion of immune suppressive M2 macrophages compared to tumor suppressive M1 macrophages in both MBMs and ECMs. Conclusions: Up-regulation of autophagy pathways was observed in pt-matched MBM vs. LN and skin mets. This finding seemed to be driven by up-regulation of GFAP and HBB, which could reflect changes in the tumor microenvironment (TME). Future studies using single-cell RNA-seq or spatial transcriptomic technology will dissect the TME. A higher M2:M1 ratio may contribute to an immune suppressive tumor microenvironment in MBM and ECM and is targetable. Validation of our findings in an independent Duke dataset is ongoing.

Trastuzumab deruxtecan (T-DXd) combinations in patients with HER2-positive advanced or metastatic breast cancer: A phase 1b/2, open-label, multicenter, dose-finding and dose-expansion study (DESTINY-Breast07)

TPS1096

Background: HER2-targeted therapies have improved survival in patients (pts) with HER2+ advanced/metastatic breast cancer (mBC) but challenges remain, including resistance to current HER2-targeted therapies. Also, additional treatment options are needed in pts with brain metastases (BM). In the phase 2 DESTINY-Breast01 trial, T-DXd demonstrated efficacy, with an objective response rate (ORR) of 61.4% and median progression-free survival (mPFS) of 19.4 mo in pts with previously treated HER2+ advanced/mBC (Modi SABCS 2020); data from an earlier cutoff of this trial supported approval of T-DXd in the US, Europe, and Japan. In a subgroup analysis of 24 pts with stable BM, T-DXd showed preliminary efficacy, with mPFS of 18.1 mo (Jerusalem ESMO Breast Cancer 2020). Here, we describe a phase 1b/2 trial evaluating the safety and preliminary antitumor activity of T-DXd monotherapy and combinations in pts with HER2+ advanced/mBC, including pts with stable and active BM. Methods: DESTINY-Breast07 (NCT04538742) is a global, multicenter, open-label, phase 1b/2 trial designed to evaluate the safety, tolerability, and preliminary antitumor activity of T-DXd monotherapy and combinations in pts with HER2+ advanced/mBC. This study consists of a T-DXd monotherapy module (module 0) and 5 combination modules of T-DXd plus (1) durvalumab, (2) pertuzumab, (3) paclitaxel, (4) durvalumab + paclitaxel, or (5) tucatinib, all in pts with no or stable BM. Two additional modules consisting of (6) T-DXd + tucatinib and (7) T-DXd monotherapy will include pts with untreated BM not requiring local therapy or previously treated BM that have progressed since local therapy (active BM). The need for chronic steroids or local therapy to manage BM symptoms is exclusionary. Modules 2 to 5 will each consist of 2 parts: dose finding (part 1) and dose expansion (part 2). Modules 0, 1, 6, and 7 will include part 2 only. Part 1 of individual modules will enroll pts who have had disease progression while receiving ≥1 prior line of therapy in the metastatic setting. In part 2, pts who have received no prior therapy (modules 0 to 5) or ≤1 prior therapy (modules 6 to 7) for metastatic disease will be randomized to receive a T-DXd combination regimen or monotherapy. The primary endpoints are determination of the recommended phase 2 doses (part 1 only) and safety and tolerability of T-DXd and combinations (parts 1 and 2). Secondary endpoints include ORR, PFS, PFS2, duration of response (DoR), and overall survival (all assessed in part 2 only) and pharmacokinetics and immunogenicity (parts 1 and 2). To assess central nervous system (CNS) activity, exploratory endpoints were added, including CNS-ORR, CNS-DoR, and CNS-PFS (by RECIST version 1.1 and RANO-BM criteria) as well as cognitive and symptom assessment using CANTAB, MDASI-BT, and NANO. Clinical trial information: NCT04538742 .

Effect of type and timing of systemic therapy on risk of radiation necrosis in patients with HER2+ breast cancer brain metastases

e14002

Background: It is estimated that 30% of patients with metastatic human epidermal growth factor receptor 2-positive (HER2+) breast cancer will develop brain metastases. Current standard of care options for HER2+ breast cancer brain metastasis (BCBrM) includes radiation therapy (stereotactic radiosurgery [SRS] or whole brain radiation), brain permeable systemic therapies, and in select cases, neurosurgical resection. A multimodal approach combining these different treatment modalities has improved the overall survival and functional outcomes of patients with BCBrM. Some HER2-directed systemic therapies, however, may increase the risk of radiation necrosis (RN), a longer-term consequence of SRS. This study explores the impact of timing and type of systemic therapies on the development of RN in patients treated with SRS for HER2+ BCBrM. Methods: This was a single-institution, retrospective study including patients ≥18 years of age with HER2+ BCBrM who received SRS between 2013 and 2018 at Duke University with at least 12-month post-SRS follow-up. Presence of RN was determined at one-year post-SRS. Demographics, radiotherapy parameters (total dose, fractions, clinical target volume [CTV], gross tumor volume [GTV], conformity index [CI], volume receiving 12 gray [V12Gy]), and timing (during [within 4 weeks of SRS] vs. not during SRS) and type of systemic therapy (HER2-directed therapy, mitosis inhibitors, DNA synthesis inhibitors, others) were evaluated. Results: Among 46 patients with HER2+ BCBrM who received SRS, 28 (60.9%) developed RN and 18 (39.1%) did not. Age at time of SRS did not differ between those who developed RN and those who did not (mean 53.3 vs 50.4 years, respectively). There was a higher percentage of African Americans in the RN group (28.6% vs 11.1%, p = 0.3). There were no significant differences between the measured radiotherapy parameters—including dose, fraction, CTV, GTV, CI, V12Gy—between the two groups (all p > 0.05). Receipt of any type of systemic therapy during SRS did not differ between patients who did or did not develop RN (60.7% vs 55.6%, p = 0.97). However, patients who developed RN more commonly received more than one line of HER2-directed therapy independent of SRS timing compared to those who did not develop RN (75.0% vs 44.4%, p = 0.08). In fact, a significantly higher proportion of those who developed RN received more than one line of HER2-directed therapy during SRS compared to those did not develop RN (35.7% vs 5.6%, p<0.05). Conclusions: Patients with HER2 BCBrM who receive multiple lines of HER2-directed therapy during SRS for BCBrM may be at higher risk of RN. This data supports a practice of holding HER2-directed therapy during SRS if medically acceptable. Further investigation of next generation HER2-directed therapies in a larger cohort of patients should be investigated to help guide best practice to minimize RN.

Identification of pathogenic CDK12 alterations in cell-free DNA (cfDNA) from patients with breast cancer

1028

Background: Cyclin dependent kinase 12 ( CDK12) has both tumor suppressive and proto-oncogenic potential in metastatic breast cancers (MBC). CDK12 may be an important biomarker and target in MBC. However, a comprehensive genomic analysis of CDK12 alterations from cfDNA in MBC has not been investigated and the genomic impact of CDK12 alterations across the MBC spectrum is unknown. The purpose of this study was to identify the incidence of CDK12 genomic alterations occurring in cfDNA from patients with MBC and elucidate which CDK12 alterations may impact CDK12 kinase activity. Methods: We queried 13,070 MBC samples from the Guardant Health database between April 2019 – November 2020 to identify the incidence of CDK12 alterations detected in cfDNA. We classified each alteration type as: missense mutations, indels, or truncations. Amino acid changes occurring at conserved regions across multiple species were identified. Three-dimensional biochemical in silico analyses with ChimeraX were used to determine which CDK12 alterations may impact CDK12 kinase activity. To gain further biologic insights into CDK12 altered MBC we made associations with CDK12 alterations and co-occurring mutated genes. Results: Nonsynonymous CDK12 alterations from the Guardant Health database were found in 317 samples from a cohort of 13,070 patients indicating an overall incidence of 2.43%. Alterations included: 239 (75.4%) missense mutations; 26 (8.2%) indels; and 52 (16.4%) truncations. We identified 62 alterations within the kinase domain with all occurring at highly conserved regions across species. The most frequent hotspot mutation identified was I76M/T, occurring in 11 unique breast cancers. Three-dimensional analyses indicate that CDK12 alterations within the hinge, HRD, DFG, catalytic spine, and regulatory spine may impact CDK12 kinase activity. The significantly co-occurring mutations from the Guardant Health breast cancer database in samples with CDK12 alterations were ARID1A, APC, RB1, and PTEN. Conclusions: A modest incidence of CDK12 genomic alterations occur in cfDNA from patients with breast cancer. Novel somatic alterations in CDK12 were identified from Guardant Health that were not detected in the public domain. A portion of these occurred at highly conserved regions across species suggesting these specific CDK12 mutations may impact CDK12 kinase expression and be actionable therapeutic targets in breast cancers. Three dimensional analyses of the CDK12 gene further illustrate which specific alterations may induce CDK12 kinase expression or lead to inactivation. Co-occurring mutations reveal a unique genotype associated with CDK12 alterations that may play a biologic role in CDK12-mediated breast cancer pathogenesis. Preclinical studies to determine the prognostic and therapeutic implication of CDK12 alterations in MBC are warranted.

Trial in progress: Phase 1a/b study of PF-07284890 (brain-penetrant BRAF inhibitor) with/without binimetinib in patients with BRAF V600-mutant solid tumors

TPS3152

Background: BRAF inhibitors have transformed treatment (Tx) for patients (pts) with BRAF V600-mutant cancers, but long-term efficacy is limited by disease progression in the brain, due to poor brain penetration. PF-07284890 is a potent, selective, highly brain-penetrant, small-molecule inhibitor of BRAF V600 mutations. This first in human study will assess the PK, safety, and preliminary clinical activity of PF-07284890, as monotherapy and in combination with binimetinib (MEK inhibitor), in pts with BRAF V600-mutated advanced solid tumors with/without brain metastases. Methods: Phase 1a/1b open-label, multicenter, dose-finding study (NCT04543188). Pts will be ≥18 y with a histologically confirmed advanced/metastatic solid tumor including primary brain tumor (PBT), confirmed BRAF V600 mutation, and presence/absence of brain involvement. Pts will have disease progression despite prior Tx without alternative Tx options. Pts with brain metastasis/PBT > 4 cm and/or symptomatic brain disease will be excluded initially, but allowed based on emerging PK. Phase 1a is a dose escalation study of PF-07284890 (monotherapy and combination). ̃35 pts will be enrolled to determine maximum tolerated dose (MTD) and/or recommended dose for expansion (RDE) of PF-07284890 (monotherapy and combination). Cohorts of 2-4 pts will be treated at each dose level of PF-07284890 until MTD/RDE determination (PF-07284890 starting dose: 50 mg QD; binimetinib 45 mg BID). Bayesian Logistic Regression Model will be used to inform dose level decisions. At least 6 pts each for monotherapy and combination will be treated at MTD/RDE. Phase 1a primary endpoints: Cycle 1 dose-limiting toxicities; MTD/RDE; AEs; lab abnormalities; and dose interruptions, modifications and discontinuations due to AEs. Secondary endpoints include PK parameters and overall response (RECIST; overall and intracranial; RANO for PBT). Phase 1b is a dose expansion and drug-drug interaction study to further evaluate PF-07284890 + binimetinib. Cohorts 1-4 (̃40 pts each) will enroll pts based on tumor type, brain involvement (asymptomatic/symptomatic), and prior Tx. Cohort 5 (̃20 pts) will include pts with any solid tumor including leptomeningeal metastases. Cohort 6 (̃10 pts) will assess the effect of PF-07284890 + binimetinib on CYP3A activity using midazolam as a substrate. Phase 1b primary endpoint: overall response (RECIST; overall and intracranial; RANO for PBT). Secondary endpoints: duration of response; progression-free survival; disease control rate; time to response; overall survival; AEs; lab abnormalities; and dose interruptions, modifications and discontinuations due to AEs; and PK parameters. For both Phase 1a and 1b, Tx will continue until disease progression, unacceptable toxicity or patient refusal. Study began enrolling pts in January 2021 and is ongoing. Clinical trial information: NCT04543188.

Genomic evaluation of tumor mutational burden-high (TMB-H) versus TMB-low (TMB-L) metastatic breast cancer to reveal unique mutational features

1091

Background: Tumor mutational burden (TMB) has emerged as an imperfect biomarker of immune checkpoint inhibition (ICI) outcomes in solid tumors. Despite the approval for pembrolizumab in all TMB-high (TMB-H) solid tumors, the optimal clinical approach to TMB-H or hypermutated advanced/metastatic breast cancer (MBC) is unknown with sparse prospective data. We hypothesize that TMB-H MBC will have unique genomic alterations compared to TMB-low (TMB-L) breast cancer that could inform novel therapeutic approaches. Methods: Tumor samples (N = 5621) obtained from patients with MBC were analyzed by next-generation sequencing (NGS) of DNA (592-gene panel or whole exome sequencing) and RNA (whole transcriptome sequencing) at Caris Life Sciences (Phoenix, AZ). TMB was calculated based on recommendations from the Friends of Cancer Research TMB Harmonization Project (Merino et al., 2020), with the TMB-H threshold set to ≥ 10 muts/Mb. IHC was performed for PD-L1 (Ventana SP142 ≥1% immune cells). Deficient mismatch repair (dMMR)/high microsatellite instability (MSI-H) was tested by IHC and NGS, respectively. Results: TMB-H was identified in 8.2% (n = 461) of MBC samples, with similar frequencies observed across molecular subtypes (7.8-8.6%, p = 0.85): HR+/HER2- (n = 3087) 7.8%, HR+/HER2+ (n = 266) 8.3%, HR-/HER2+ (n = 179) 7.8%, TNBC (n = 1476) 8.6%. The frequency of TMB-H was significantly increased in lobular (16%) versus ductal (5%) MBC (p < 0.01). TMB-H samples were enriched in genitourinary (42%), soft tissue (20%), and gastrointestinal non-liver (16%) biopsy specimens. Compared to TMB-L tumors, TMB-H tumors exhibited significantly higher mutation rates for TP53 (60 v 52%), PIK3CA (55 vs 31%), ARID1A (34 vs 11%), CDH1 (27 vs 11%), NF1 (22 vs 9%), RB1 (14 vs 5%), KMT2C (12 vs 7%), PTEN (12 vs 7%), ERBB2 (7 vs 2.9%), and PALB2 (3.3 vs 1%) genes (p < 0.05 each). Copy number alteration and fusion rates did not differ between TMB-H and TMB-L breast cancers. PI3K/AKT/MTOR, TP53, Histone/Chromatin remodeling, DNA damage repair (DDR), RAS, and cell cycle pathway alterations were detected in > 25% TMB-H MBCs (p < 0.05 each). dMMR/MSI-High (7.2 vs 0.3%, p < 0.01) and PD-L1 positivity (36 vs 28%, p < 0.05) frequencies were significantly increased in TMB-H tumors. DNA signature analyses including APOBEC and homologous recombination repair deficiency, as well as gene expression profiling to assess immune-related signatures and tumor microenvironment are underway. Conclusions: TMB-H breast cancers contain a unique genomic profile enriched with targetable mutations such as PIK3CA, ARID1A, NF1, PTEN, ERBB2, and PALB2. Concurrent predictive biomarkers of response to immune checkpoint inhibition such as MSI-H and PDL-1 positivity are also more prevalent in TMB-H MBC. These findings suggest novel combination strategies within TMB-H MBC could be explored.

Salting the Soil: Targeting the Microenvironment of Brain Metastases

Paget's "seed and soil" hypothesis of metastatic spread has acted as a foundation of the field for over a century, with continued evolution as mechanisms of the process have been elucidated. The central nervous system (CNS) presents a unique soil through this lens, relatively isolated from peripheral circulation and immune surveillance with distinct cellular and structural composition. Research in primary and metastatic brain tumors has demonstrated that this tumor microenvironment (TME) plays an essential role in the growth of CNS tumors. In each case, the cancerous cells develop complex and bidirectional relationships that reorganize the local TME and reprogram the CNS cells, including endothelial cells, pericytes, astrocytes, microglia, infiltrating monocytes, and lymphocytes. These interactions create a structurally and immunologically permissive TME with malignant processes promoting positive feedback loops and systemic consequences. Strategies to interrupt interactions with the native CNS components, on "salting the soil," to create an inhospitable environment are promising in the preclinical setting. This review aims to examine the general and specific pathways thus far investigated in brain metastases and related work in glioma to identify targetable mechanisms that may have general application across the spectrum of intracranial tumors.

Inpatient palliative care utilization for patients with brain metastases

Introduction

Given the high symptom burden and complex clinical decision making associated with a diagnosis of brain metastases (BM), specialty palliative care (PC) can meaningfully improve patient quality of life. However, no prior study has formally evaluated patient-specific factors associated with PC consultation among BM patients.

Methods

We examined the rates of PC consults in a cohort of 1303 patients with BM admitted to three tertiary medical centers from October 2015 to December 2018. Patient demographics, surgical status, 30-day readmission, and death data were collected via retrospective chart review. PC utilization was assessed by identifying encounters for which an inpatient consult to PC was placed. Statistical analyses were performed to compare characteristics and outcomes between patients who did and did not receive PC consults.

Results

We analyzed 1303 patients admitted to the hospital with BM. The average overall rate of inpatient PC consultation was 19.6%. Rates of PC utilization differed significantly by patient race (17.5% in White/Caucasian vs 26.0% in Black/African American patients, P = .0014). Patients who received surgery during their admission had significantly lower rates of PC consultation (3.9% vs 22.4%, P < .0001). Patients who either died during their admission or were discharged to hospice had significantly higher rates of PC than those who were discharged home or to rehabilitation (P < .0001).

Conclusions

In our dataset, PC consultation rates varied by patient demographic, surgical status, discharging service, and practice setting. Further work is needed to identify the specific barriers to optimally utilizing specialty PC in this population.

What's the Price? Toxicities of Targeted Therapies in Breast Cancer Care

Agents with mechanisms novel to breast cancer care have been approved to treat breast cancer. These agents include drugs that target cyclin-dependent kinases, phosphoinositide 3-kinase PI3KCA gene mutations, PARP, checkpoint regulation, and novel antibody-drug conjugates. However, these novel approaches bring a risk of toxicities quite different from those of conventional cytotoxic chemotherapy. Here, we review these agents and discuss related adverse events, with particular attention to endocrine, pulmonary, and dermatologic toxicities. Endocrine toxicities associated with novel cancer therapies for breast cancer are distinct and often present with symptoms related to the specific hormonal deficiencies and rarely hormonal excess. Given the complex and sometimes irreversible nature of these toxicities, once recognized, transdisciplinary management with an endocrinologist experienced with managing drug-related toxicities is encouraged. Drug-related pneumonitis is a serious concern with new targeted therapies. Presentation may not be easily distinguished, and a multidisciplinary team approach can optimize patient care. Heightened awareness is crucial for early detection and treatment. Management should follow recommendations provided by the National Cancer Institute Common Terminology Criteria for Adverse Events and agent-specific guidelines. Cutaneous toxicities from anticancer therapies represent a common and often poorly characterized challenge for patients with breast cancer. Although our understanding of dermatologic effects from novel therapies continues to improve, the breadth of toxicities spans all dermatologic conditions. Targeted therapies offer effective and often novel therapeutic strategies for patients with breast cancer but also bring new adverse event profiles. In this era, it will be important both to closely follow monitoring recommendations and to remain vigilant for emerging toxicities.

Effects of Breast Cancer Adjuvant Chemotherapy Regimens on Expression of the Aging Biomarker, p16INK4a

BACKGROUND

Although chemotherapy saves lives, increasing evidence shows that chemotherapy accelerates aging. We previously demonstrated that mRNA expression of p16INK4a , a biomarker of senescence and molecular aging, increased early and dramatically after beginning adjuvant anthracycline-based regimens in early stage breast cancer patients. Here, we determined if changes in p16INK4a expression vary by chemotherapy regimen among early stage breast cancer patients.

METHODS

We conducted a study of stage I-III breast cancer patients receiving adjuvant or neoadjuvant chemotherapy. p16INK4a expression was analyzed prechemotherapy and postchemotherapy (median 6.2 months after the last chemotherapy) in peripheral blood T lymphocytes. Chemotherapy-induced change in p16INK4a expression was compared among regimens. All statistical tests were 2-sided.

RESULTS

In 146 women, chemotherapy was associated with a statistically significant increase in p16INK4a expression (accelerated aging of 17 years; P < .001). Anthracycline-based regimens were associated with the largest increases (accelerated aging of 23 to 26 years; P ≤ .008). Nonanthracycline-based regimens demonstrated a much smaller increase (accelerated aging of 9 to 11 years; P ≤ .15). In addition to the type of chemotherapy regimen, baseline p16INK4a levels, but not chronologic age or race, were also associated with the magnitude of increases in p16INK4a . Patients with lower p16INK4a levels at baseline were more likely to experience larger increases.

CONCLUSIONS

Our findings suggest that the aging effects of chemotherapy may be influenced by both chemotherapy type and the patient's baseline p16INK4a level. Measurement of p16INK4a expression is not currently available in the clinic, but nonanthracycline regimens offering similar efficacy as anthracycline regimens might be favored.

Brain Metastasis Cell Lines Panel: A Public Resource of Organotropic Cell Lines

Spread of cancer to the brain remains an unmet clinical need in spite of the increasing number of cases among patients with lung, breast cancer, and melanoma most notably. Although research on brain metastasis was considered a minor aspect in the past due to its untreatable nature and invariable lethality, nowadays, limited but encouraging examples have questioned this statement, making it more attractive for basic and clinical researchers. Evidences of its own biological identity (i.e., specific microenvironment) and particular therapeutic requirements (i.e., presence of blood-brain barrier, blood-tumor barrier, molecular differences with the primary tumor) are thought to be critical aspects that must be functionally exploited using preclinical models. We present the coordinated effort of 19 laboratories to compile comprehensive information related to brain metastasis experimental models. Each laboratory has provided details on the cancer cell lines they have generated or characterized as being capable of forming metastatic colonies in the brain, as well as principle methodologies of brain metastasis research. The Brain Metastasis Cell Lines Panel (BrMPanel) represents the first of its class and includes information about the cell line, how tropism to the brain was established, and the behavior of each model in vivo. These and other aspects described are intended to assist investigators in choosing the most suitable cell line for research on brain metastasis. The main goal of this effort is to facilitate research on this unmet clinical need, to improve models through a collaborative environment, and to promote the exchange of information on these valuable resources.

HER2‐positive breast cancer brain metastasis: A new and exciting landscape

Background

Brain metastases (BrM) incidence is 25% to 50% in women with advanced human epidermal growth factor receptor 2 (HER2)‐positive breast cancer. Radiation and surgery are currently the main local treatment approaches for central nervous system (CNS) metastases. Systemic anti‐HER2 therapy following a diagnosis of BrM improves outcomes. Previous preclinical data has helped elucidate HER2 brain trophism, the blood‐brain/blood‐tumor barrier(s), and the brain tumor microenvironment, all of which can lead to development of novel therapeutic options.

Recent findings

Several anti‐HER2 agents are currently available and reviewed here, some of which have recently shown promising effects in BrM patients, specifically. New strategies driven by and focusing on brain metastasis‐specific genomics, immunotherapy, and preventive strategies have shown promising results and are under development.

Conclusions

The field of HER2+ breast cancer, particularly for BrM, continues to evolve as new therapeutic strategies show promising results in recent clinical trials. Increasing inclusion of patients with BrM in clinical studies, and a focus on assessing their outcomes both intracranially and extracranially, is changing the landscape for patients with HER2+ CNS metastases by demonstrating the ability of newer agents to improve outcomes.