Updates on Molecular Targeted Therapies for Intraparenchymal CNS Metastases

Central nervous system (CNS) metastases can occur in a high percentage of systemic cancer patients and is a major cause of morbidity and mortality in these patients. Almost any histology can find its way to the brain, but lung, breast, and melanoma are the most common pathologies seen in the CNS from metastatic disease. Identification of many key targets in the tumorigenesis pathway has been crucial to the development of a number of drugs that have demonstrated successful penetration of the blood–brain, blood–cerebrospinal fluid, and blood–tumor barriers. Targeted therapy and immunotherapy have dramatically revolutionized the field with treatment options that can provide successful and durable control of even CNS disease. In this review, we discuss major targets with successful treatment options as demonstrated in clinical trials. These include tyrosine kinase inhibitors, monoclonal antibodies, and antibody–drug conjugates. We also provide an update on the state of the field and highlight key upcoming trials. Patient-specific molecular information combined with novel therapeutic approaches and new agents has demonstrated and continues to promise significant progress in the management of patients with CNS metastases.

Local and Systemic Therapy in Breast Cancer Patients with Central Nervous System Metastases

Purpose As survival of patients with central nervous system (CNS) metastases from breast cancer is poor and incidence rates are increasing, there is a growing need for better treatment strategies. In the current study, the efficacy of local and systemic therapies was analyzed in breast cancer patients with CNS metastases.Methods Medical records from patients with breast cancer and brain and/or leptomeningeal metastases treated at a tertiary referral center and a teaching hospital between 2010 and 2020 were retrospectively studied. Main outcomes of interest were overall survival and CNS progression free survival. Analyses were performed for the different systemic and local therapies for CNS metastases, and subgroups based on breast cancer subtypes and brain metastases vs leptomeningeal metastases were tested.Results We identified 155 patients, 44 HER2-positive, 68 hormone receptor positive/HER2-negative and 43 triple negative. Median overall survival was 5.9 months for all 155 analyzed patients. Survival differed significantly between breast cancer subtypes (HER2-positive 22.8 months, hormone receptor positive/HER2-negative 2.4 months, triple negative 4.2 months, P<0.001). Patients receiving a combination of local and systemic therapy demonstrated prolonged median overall survival (18.5 months) as compared to local therapy only (5.7 months) or systemic therapy only (4.3 months, P<0.001). No significant difference in overall survival was observed between different systemic treatment regimens.Conclusion Breast cancer patients with CNS metastases show longest median overall survival when the subtype is HER2-positive and when they are treated with both local and systemic therapy.

CTNI-01. A PHASE 1-2 CLINICAL TRIAL OF EO1001 (APL-122), A NOVEL IRREVERSIBLE PAN-ERBB INHIBITOR WITH PROMISING BRAIN PENETRATION

CNS metastases are a prominent driver of cancer morbidity and mortality, especially as targeted therapies have improved systemic outcomes. Mutations in the ErbB/HER kinase family are known oncodrivers in many cancers. Extensive crosstalk among ErbB/HER receptors suggests that inhibition of multiple family members may benefit treatment and limit drug resistance. There is a desperate need for new agents that are more tolerable and effective in treating CNS metastases. EO1001 (APL-122) is a first-in-class, oral, irreversible pan-ErbB inhibitor targeting ErbB1, ErbB2 and ErbB4 with promising CNS penetration in preclinical models. Preclinical data suggests a favorable pharmacokinetic and safety profile and activity against ErbB-driven cancers in patient-derived xenograft models. We report on a first-in-human Phase 1-2 clinical trial in progress. Adult participants with confirmed ErbB-positive cancer, including patients with CNS involvement, who have progressed after standard-of-care, with adequate bone marrow, renal and liver function are eligible. ESCALATION: One subject per dose cohort is enrolled in an accelerated dose-escalation design until drug-related toxicity (≥G2) is observed in the first cycle, after which dose escalation will revert to a 3 + 3 design to determine the maximum tolerated dose (MTD). Cycle 1: Patients receive a single oral dose of EO1001 on day 1; single-dose pharmacokinetics are measured. Beginning on day 8, EO1001 is administered once daily for 21 days; multi-dose pharmacokinetics are measured. Cycles 2-6: EO1001 is administered once daily in continuous 28-day cycles for up to 20 weeks. EXPANSION: EO1001 will be administered once daily to 20 patients at the MTD in continuous 28-day cycles for up to 6 cycles to determine a recommended Phase 2 dose (RP2D) for further study. Toxicity is assessed based on NCI CTCAEv5 and tumor response is assessed by RECIST 1.1. CNS exposure is evaluated in patients via CSF collection with confirmed CNS disease involvement.

Exclusion criteria of breast cancer research protocols: A descriptive analysis.

82 Background: Clinical trials play an important role in advancing cancer treatments. Unfortunately, only about 3% of adults with cancer are enrolled in a clinical trial in the United States due to various barriers to enrollment. This includes restrictive eligibility criteria, which currently have no standard guidelines. The purpose of this study is to evaluate the variability of eligibility criteria. Methods: This descriptive analysis utilized all therapeutic breast protocols offered at the University of Alabama at Birmingham (UAB) between 2004-2020. Exclusion criteria (e.g., laboratory values and comorbidities) were extracted from protocols using OnCore, an online dataset used to manage clinical trials, and ClinicalTrials.gov. Laboratory values or vital signs analyzed included liver function tests, hematologic labs, Eastern Cooperative Oncology Group (ECOG) performance status, and hypertension. Comorbid conditions included congestive heart failure, cardiovascular disease, presence of central nervous system (CNS) metastases, and history of prior cancer. Comorbid conditions were further analyzed by amount of time protocols required participants to be from initial diagnosis or exacerbation-free. Results: There were a total of 102 eligible protocols. Substantial heterogeneity was observed in exclusion criteria across liver/hematologic laboratory values and demographic/comorbidity variables. Among liver laboratory values, most protocols included an upper limit of acceptable for bilirubin (78%): 9% used the institutional upper limit of normal (ULN), 2% used 1.2xULN, 3% used 1.25xULN, 56% used 1.5xULN, 6% used 2xULN, and 2% used 3xULN. Similar variability was observed in protocols that included alanine transaminase and aspartate transaminase. Among hematological labs, 82% of protocols defined a lower limit of acceptable absolute neutrophil count: 1% 500mcL, 11% used 1,000mcL, 4% used 1,200mcL, 1% used 1,250mcL, 64% used 1,500mcL, and 1% used 1,800mcL. Of the comorbid conditions, exclusion criteria varied for congestive heart failure (49%), an acute exacerbation of cardiovascular disease (80%), CNS metastases (59%) and a prior cancer (66%). While most protocols included cardiovascular disease, the allowable timeframe varied between protocols: 4% did not allow an acute exacerbation within the previous 3 months, 32% did not allow within the previous 6 months, 5% did not allow within the previous 12 months, and 38 % did not specify a time frame. Protocols including history of a prior cancer as a criterion similarly had varied definitions based on timeline. Conclusions: Substantial heterogeneity was observed among clinical trial protocols. While exclusion criteria are necessary for patient safety, there is lack of evidence for current parameters. Future research should focus on defining standardized eligibility criteria while allowing for deviation based on drug specificity.

Evaluating specialty referral, research involvement, and PROs in a CNS-involved metastatic breast cancer care coordination program.

47 Background: Central nervous system (CNS) metastases are associated with decreased survival and quality of life for patients with metastatic breast cancer (MBC). Multi-disciplinary care can optimize outcomes. This project aims to improve access to coordinated care for patients with MBC and CNS metastases while assessing patient-reported outcomes (PROs) in the context of the multidisciplinary care experience. Methods: Patients with MBC and CNS metastases are referred and offered to enroll in our care coordination program. A team of specialists (breast medical oncology, breast cancer genetics, radiation oncology, neurosurgery, neuro-oncology, physical medicine and rehabilitation (PM&R), neuropsychology, and palliative care) supports a dedicated program coordinator who provides navigation, education, specialty referral, and clinical trial screening. A unique intake form developed for the program creates personalized, coordinated, and expedited referrals. PROs and caregiver assessments are collected on a voluntary basis using the following validated questionnaires: PROMIS Cancer Function Brief 3D Profile, MD Anderson Symptom Inventory Brain Tumor (MDASI), and Short Form Zarit Burden Interview (ZBI-12), a screening tool for caregiver burden. Results: Since May 2020, 43 patients were referred and a total of 40 patients (93%) were enrolled – 2 (5%) declined due to perceived burden of participation and 1 (2%) died before enrollment. The majority of patients were White (n = 34, 85%). Median time to program intake was 1 day (range: 0-8 days). Of the 43 patients referred, 17 (40%) consented to research studies in the metastatic setting. 11 were for an interventional trial (65%), while 9 consents were for non-interventional studies (53%). In addition to the initially referred specialty, 56 referrals were made across 7 sub-specialties; 37 patients (66%) were subsequently seen by a sub-specialist, most commonly radiation oncology (n = 9), PM&R (n = 9), neuro-oncology (n = 8), and neuropsychology (n = 8). Of the nine patients seen by PM&R, 5 completed the PROMIS Profile (55%). Similar completion rates were seen for the MDASI (13 of 23 surveys given, 56.5%) and ZBI-12 (13 of 26 surveys given, 50%) questionnaires. Conclusions: Implementation of a care coordination program for patients with MBC and CNS metastases allows for improved access to care across sub-specialties and supports participation in clinical research for a group of cancer patients historically underrepresented in research studies. Though completion of questionnaires is optional in this program, the rate of completion raises the question of whether this patient population faces unique challenges that make it difficult to complete questionnaires that are often required in research studies. Funding source: National Comprehensive Cancer Network Oncology Research Program from financial support from Pfizer.

Exclusion Criteria of Breast Cancer Clinical Trial Protocols: A Descriptive Analysis

Purpose: 3-8% of US adults with cancer are enrolled in a clinical trial due to various barriers to enrollment. The purpose of this study is to evaluate the variability of eligibility criteria, which currently have no standard guidelines.Methods: This descriptive analysis utilized all therapeutic breast protocols offered at the University of Alabama at Birmingham between 2004-2020. Exclusion criteria were abstracted using OnCore and ClinicalTrials.gov. Laboratory values included liver function tests and hematologic labs. Comorbid conditions included congestive heart failure, cardiovascular disease, central nervous system (CNS) metastases, and prior cancer history. Comorbid conditions were further analyzed by amount of time protocols required participants to be from diagnosis or exacerbation-free.Results: 102 protocols were eligible. Among liver laboratory values, bilirubin (78%) was included in most protocols ranging from institutional upper limit of normal (ULN) (9%) to 3xULN (2%), with 1.5xULN (56%) being most common. Similar variability was observed in alanine transaminase and aspartate transaminase. Among hematological labs, 82% of protocols defined a lower limit of acceptable absolute neutrophil count ranging from 500μL (1%) to 1,800μL (1%), with 1,500μL (64%) being most common. Of the comorbid conditions, exclusion criteria varied for congestive heart failure (49%), an acute exacerbation of cardiovascular disease (80%), CNS metastases (59%) and a prior cancer (66%). The allowable timeframe varied between protocols for cardiovascular disease and prior cancer.Conclusion: Substantial heterogeneity was observed across laboratory values and comorbid variables among protocols. Future research should focus on defining standardized eligibility criteria while allowing for deviation based on drug specificity.

SYST-06. PHASE II TRIAL OF PAXALISIB (GDC-0084) IN COMBINATION WITH TRASTUZUMAB FOR PATIENTS WITH HER2-POSITIVE BREAST CANCER BRAIN METASTASES (BCBM)

BACKGROUND The PI3K/Akt/mTOR is an important pathway in BCBM. Mutations in PIK3CA or PTEN loss are associated with trastuzumab resistance. Inhibition of PI3K and mTOR led to durable responses in 3 of 5 patient-derived xenografts (PDX) models of BCBM. Paxalisib is a potent, brain-penetrant inhibitor of class I PI3K and mTOR. METHODS This is a single-center, phase II study to evaluate the efficacy of the combination of paxalisib with trastuzumab for the treatment of central nervous system (CNS) metastases in patients with HER2-positive breast cancer. Patients will receive paxalisib (45 mg daily) and trastuzumab (8 mg/kg loading dose, then 6 mg/kg every 3 weeks). Two cohorts will be enrolled: Cohort A: a single-arm, two-stage, phase II cohort; and Cohort B: a pre-surgical window cohort. Inclusion criteria include unequivocal evidence of new and/or progressive HER2-positive CNS metastases, at least one measurable (≥10 mm) CNS metastasis (Cohort A), clinical indication for CNS metastasis resection (Cohort B). Primary endpoint for Cohort A is objective response rate (ORR) in the CNS per Response Assessment in Neuro-Oncology Brain Metastases (RANO-BM) criteria. For Cohort B, the primary endpoint is the correlation between p4EBP1 levels in the resected CNS tumor tissue from patients and intracranial response to paxalisib/trastuzumab in the PDX model generated from the same patient. Secondary endpoints include overall survival, safety and patient-reported outcomes. Mandatory blood and cerebrospinal fluid with optional tumor biopsy will be collected at baseline, on-treatment and at progression. In Cohort A, we will enroll 37 patients in a Simon two-stage design. If ≥4 responses are seen, the regimen will be considered successful. This design has 90% power with alpha &lt;10%. Cohort B will enroll 10 patients. The trial opened in February, 2019 and 8 patients have been enrolled. NCT03765983.

Gamma Knife Radiosurgery-Based Combination Treatment Strategies Improve Survival in Patients With Central Nervous System Metastases From Epithelial Ovarian Cancer: A Retrospective Analysis of Two Academic Institutions in Korea and Taiwan

Central nervous system (CNS) metastases from epithelial ovarian cancer (EOC) are rare. We investigated the clinico-pathological prognostic factors of patients with CNS metastases from EOC and compared the outcomes of various treatment modalities. We retrospectively reviewed the records of patients with CNS metastases from EOC between 2000 and 2020. Information on the clinical and pathological characteristics, treatment, and outcomes of these patients was retrieved from Samsung Medical Center and National Taiwan University Hospital. A total of 94 patients with CNS metastases were identified among 6,300 cases of EOC, resulting in an incidence of 1.49%. Serous histological type [hazard ratio (HR): 0.49 (95% confidence interval [CI] 0.25-0.95), p=0.03], progressive disease [HR: 2.29 (95% CI 1.16-4.54), p=0.01], CNS involvement in first disease relapse [HR: 0.36 (95% CI 0.18-0.70), p=0.002], and gamma knife radiosurgery (GKS)-based combination treatment for EOC patients with CNS lesions [HR: 0.59 (95% CI 0.44-0.79), p&lt;0.001] significantly impacted survival after diagnosis of CNS metastases. In a subgroup analysis, superior survival was observed in patients with CNS involvement not in first tumor recurrence who underwent GKS-based combination therapeutic regimens. The survival benefit of GKS-based treatment was not significant in patients with CNS involvement in first disease relapse, but a trend for longer survival was still observed. In conclusion, GKS-based combination treatment can be considered for the treatment of EOC patients with CNS metastases. The patients with CNS involvement not in first disease relapse could significantly benefit from GKS-based combination strategies.