O’Sullivan, Ciara C.

Abstract PURPOSE: Treatment options for patients (pts) with HER2+ BCBM remain limited. We previously reported that neratinib monotherapy is associated with a volumetric central nervous system objective response rate (CNS ORR) of 8%, whereas the combination of neratinib and capecitabine resulted in a volumetric CNS ORR of 49% (in lapatinib-naïve pts). Preclinical data suggest that neratinib may overcome resistance to trastuzumab-emtansine (T-DM1) and that the combination has potential CNS efficacy. Here, we report results of neratinib plus T-DM1 in pts with HER2+ BCBM. PATIENTS AND METHODS: In this prospective, multicenter, phase II study, pts with measurable HER2+ BCBM received neratinib 160 mg orally once daily plus T-DM1 3.6 mg/kg IV every 21 days in three parallel-enrolling cohorts. Cohort 4A enrolled pts with previously untreated brain metastases. Cohort 4B enrolled pts with BCBM progressing after prior local CNS-directed therapy without prior exposure to T-DM1. Cohort 4C enrolled pts with BCBM progressing after prior local CNS-directed therapy who had previous exposure to T-DM1. Diarrhea prophylaxis with colestipol and loperamide was required during cycle 1. Cohorts 4A and 4B were single-stage with a planned enrollment of 20 patients; cohort 4C had a two-stage design, with a requirement for at least 1 of the first 9 pts to achieve a response in order to enroll a total of 24 patients. The primary endpoint was Response Assessment in Neuro-Oncology-Brain Metastases (RANO BM) in each cohort separately. Correlative studies included patient-reported outcomes (PROs) for gastrointestinal toxicity. RESULTS: We enrolled 6, 17, and 21 patients to cohorts 4A, 4B, and 4C, during 11/07/2018 – 11/01/2021. Enrollment was stopped prematurely due to slow accrual. Across Cohorts 4A-4C, the median number of prior lines of chemotherapy prior to enrollment was 2 (range 1-10); 25% received prior lapatinib and no patients received prior tucatinib. In cohorts 4B and 4C (prior CNS-treated cohorts), 33% had prior CNS surgery and >94% had prior CNS radiation. Among evaluable patients, CNS ORR in cohorts 4A (n=6), 4B (n=16), and 4C (n=21) was 50.0% (95% CI 18.8- 81.2%), 25.0% (95% CI 8.3-52.6%), and 38.1% (95% CI 19.0-61.3%), respectively. Median (range) number of cycles completed for 4A, 4B, and 4C was 4.5 (1-15), 4 (range 0-49+), and 6 (0-23); three patients on Cohort 4B remain on protocol therapy (cycles 14, 45, and 49). The overall survival at 12-months for cohorts 4A, 4B, and 4C was 83.3% (95% CI, 58.3-100%), 86.2% (95% CI 70-100%), and 83.3% (95% CI 67.6-100%). Diarrhea was the most common grade 3 toxicity (19.0–33.3% across cohorts); one grade 4 liver function event occurred in cohort 4B. Updated efficacy results will be reported at the meeting; PRO analyses are ongoing. CONCLUSION: Intracranial activity was observed for the combination of neratinib plus T-DM1 across all three enrolled cohorts, including those with prior T-DM1 exposure, suggesting synergistic effects of this treatment combination. Our data provide additional evidence for consideration of neratinib-based combinations in pts with HER2+ BCBM. Citation Format: Rachel Freedman, Siyang Ren, Nabihah Tayob, Rebecca Gelman, Karen L. Smith, Raechel Davis, Alyssa Pereslete, Victoria Attaya, Christine Cotter, Wendy Y. Chen, Cesar Augusto Santa-Maria, Catherine Van Poznak, Beverly Moy, Adam M. Brufsky, Michelle Melisko, Ciara C. O’Sullivan, Nadia Ashai, Yasmeen Rauf, Julie Nangia, Dario Trapani, Jennifer Savoie, Robyn Burns, Antonio C. Wolff, Eric Winer, Mothaffar Rimawi, Ian Krop, Nancy U. Lin. Translational Breast Cancer Research Consortium Trial 022: Neratinib and Trastuzumab-Emtansine for HER2+ Breast Cancer Brain Metastases (BCBM) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD7-03.

Abstract Background: Two poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPi) are currently FDA-approved for the treatment of HER2-negative metastatic breast cancer (MBC) in carriers of germline pathogenic variants (PVs) in BRCA1 or BRCA2 (BRCA1/2). This study explores the clinical outcomes of MBC patients treated with a PARPi. Methods: In this retrospective study, we included MBC patients treated with a PARPi between January 2017 and February 2022 at Mayo Clinic (Minnesota, Arizona, Florida, and Mayo Clinic Health Systems). We used the Kaplan Meier method to estimate the time-to-treatment-failure (TTF) and the log-rank test to compare different subsets. In addition, predictors of TTF were identified in a multivariate cox-proportional hazard regression model, including age at PARPi initiation, race, ethnicity, histology, estrogen receptor (ER), progesterone receptor (PR), and HER2 expression of the tumor, the number of prior therapies, type of PARPi, and PV carrier status (germline BRCA1/2 or PALB2 vs. somatic BRCA1/2 vs. other). Results: Sixty-five patients treated with PARPi (olaparib: 51; talazoparib: 14) were included in the final analysis. Fifty-five patients were carriers of germline PVs in BRCA1 (n=24, 37%), BRCA2 (n=27, 42%) or PALB2 (n=4, 6%), whereas ten patients (15%) had no germline PVs but the tumor had a somatic mutation in the homologous recombination-related (HRR) genes (7 in BRCA1/2, 2 in ATM, and 1 in CDKN2A and CDH1). At the data cutoff, 48 (74%) patients had discontinued PARPi due to progression or death. Fifteen (23%) patients required a dose reduction due to side effects. Occurrence of grade ≥ 3 side effects: anemia in 8, fatigue in 4, neutropenia in 2, and thrombocytopenia in 2 patients. Eight (15.7%) patients in the olaparib group and seven (50%) patients in the talazoparib group required a dose reduction for side effects. No patient on olaparib required drug discontinuation due to side effects, whereas two patients on talazoparib were switched to olaparib due to cytopenias and could tolerate olaparib. Median TTF in the overall population was 8 months (95% confidence interval [CI]: 6.4 – 9.6), and there was no difference (p=0.64) in TTF between the olaparib and talazoparib groups. Median TTF in the germline BRCA1, BRCA2, and PALB2 PV carriers were 7, 8, and 11 months, respectively (p=0.57). Among patients with somatic BRCA1/2 mutations, the median TTF was 4 months. Numerically, patients with HER2-positive tumors (n=8) had a shorter TTF compared to HER2-negative tumors (Median TTF: 4 vs. 8 months, p=0.098). No significant difference in TTF was observed by ER or PR status of the tumor, age at initiation of PARPi, the number of prior therapies, and prior use of platinum-based chemotherapy or CDK4/6 inhibitors. In multivariate analysis, HER2 positivity (hazard ratio [HR]: 8.0, 95% CI: 2.2 – 29.4, p=0.002), somatic BRCA1/2 mutations (HR: 7.6, 95% CI: 1.2 – 50.0, p=0.03) and somatic mutations in other HRR genes (HR: 19.1, 95% CI: 3.1 – 118.6, p=0.002) were associated with worse TTF. Conclusions: In the real world, PARPi were well-tolerated with promising time-to-treatment-failure (TTF) benefits comparable to data from clinical trials. Notably, relatively shorter TTF was observed in patients with somatic BRCA1/2 and other HRR gene mutations and HER2-positive MBC. These findings improve our understanding of the role of PARPi in MBC and will help to guide treatment decisions with PARPi in the clinical setting. Citation Format: Nusrat Jahan, Jodi Taraba, Karthik V. Giridhar, Roberto A. Leon-Ferre, Amye J. Tevaarwerk, Elizabeth Cathcart-Rake, Ciara C. O’Sullivan, Prema Peethambaram, Timothy J. Hobday, Kathryn Ruddy, Lida A. Mina, Pooja Advani, Felipe Batalini, Matthew P. Goetz, Tufia C. Haddad, Fergus J. Couch, Siddhartha Yadav. Clinical outcomes of metastatic breast cancer patients treated with poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPi): the Mayo Clinic experience [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-01-22.

Abstract Background: The high-level aims of the Advocate-BREAST study are to study and improve the overall experience of patients with breast cancer (BC) through education, shared decision making, and patient-centered clinical trials. Assessing areas of unmet need in care delivery and research as identified by patients with BC will direct future research and help us improve the patient experience. Methods: In April 2022, an electronic RedCap survey was circulated to 6,918 BC survivors (stage 0-4 disease) enrolled in the prospectively consented Mayo Clinic Breast Disease Registry (MCBDR), which includes rural-dwelling women often underrepresented in cancer care delivery research. The questionnaire asked about satisfaction with multiple aspects of cancer care delivery and the education and support patients receive(d) regarding practical, financial, emotional, societal and spiritual concerns linked to BC. Patients were also asked to rank potential Quality Improvement (QI) projects in order of the likelihood the proposal could improve quality of life for BC patients and their families. Questions regarding clinical trial participation, use of integrative medicine and perspectives on medical second opinions were also included. Responses were collected via anonymous local language questionnaires. Results: The survey received 2,451 responses from MCBDR enrollees. 13% of respondents had Ductal Carcinoma in Situ (DCIS), 83% had early breast cancer (EBC) (Stage 1-3) and 4% had metastatic breast cancer (MBC). Mean age was 64 (SD 11.9), and mean time in months since diagnosis was 93 (SD 1.42). 69.3 % of patients received all care at Mayo Clinic; 24.7% at Mayo and another healthcare organization, and 6% at a non-Mayo site. Although the overall experience of care was generally good/excellent (> 90 %), gaps were perceived in terms of information provision, continuity of care (including survivorship care after 5 years), navigating care transitions, and timely access to mental health resources. The main severe symptoms patients recalled in year 1 were hair loss, eyebrow/eyelash thinning, hot flashes, sexual dysfunction and cognitive issues. The main concerns patients recalled in the first year following diagnosis were fear of BC recurrence and spread as well as of dying, practical and emotional concerns for family members if they were to die of BC, and their emotional health. Patients were most dissatisfied with information and support related to management of lymphedema, sexual dysfunction, eyebrow/eyelash thinning, and peripheral neuropathy. Respondents overwhelmingly voiced the need for the following QI projects: i) lifetime access to online patient educational resources: including summary “cheat sheets”; ii) educational, practical, emotional and holistic support programs for MBC patients, and iii) BC Wellness Programs for EBC and MBC patients (endorsed by 82.6%; 82.4% and 81.9% of respondents, respectively). Predictors in terms of age, time since diagnosis, and cancer stage that may account for satisfaction with care, concerns, or QI preferences will be reported at the meeting. Of 20% of patients who saw an Integrative Medicine provider, 85% were satisfied/very satisfied with the care received. Of ~40% of patients who received a second opinion regarding their BC diagnosis and treatment plan, 96% found this beneficial. 47% of respondents had participated in a clinical trial, which is higher than seen in the general population such that conclusions may not be generalizable. Of those who had not participated in a study, 30% reported that they were unsure if they would participate in a trial if offered, and 9% reported that they would decline same. Conclusion: Understanding the lived experiences of persons with BC is essential to improve quality of care. Patients with early and advanced BC desire holistic care, continuity of care, concise educational resources and early psychological support. Citation Format: Kathryn Ruddy, Ciara C. O’Sullivan, Nicole Larson, Robert A. Vierkant, Mary Lou Smith, Cynthia Chauhan, Fergus J. Couch, Janet Olson. Advocate-BREAST: Advocates and Patients’ Advice to Enhance Breast Cancer Care Delivery, Patient Experience and Patient Centered Research by 2025 [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-05-41.

Abstract Introduction: Use of long-term endocrine therapy (ET) for ER+ breast cancer often leads to acquired ESR1 mutations (mutESR1), causing endocrine resistance, tumor progression, and poor prognosis. An unmet clinical need exists for treating ER+ mBC patients with mutESR1, particularly after progression on CDK4/6 inhibitors (CDK4/6i). ELAINE 2 is an open-label, phase 2, multicenter trial evaluating safety and efficacy of lasofoxifene (LAS [selective estrogen receptor modulator]) plus abemaciclib (Abema [CDK4/6i], provided by Eli Lilly) in patients with ER+/HER2- and mutESR1 mBC who progressed after prior ET. Preliminary data with LAS plus Abema showed median progression-free survival of 55.7 wks, objective response rate of 50%, and 24-wk clinical benefit (CB) rate of 69%, with an acceptable safety and tolerability profile. Here, we report ESR1 ctDNA mutant allele frequency (MAF) and correlations of ESR1 MAF changes with CB. Methods: ELAINE 2 patients with detectable ctDNA mutESR1 at baseline (BL) were analyzed. Oral LAS 5 mg/day and Abema 150 mg BID were taken until disease progression, death, unacceptable toxicity, or withdrawal from the study. ctDNA was assessed by the Sysmex-Inostics SafeSeq assay—which detects mutESR1 at low allele fractions—at BL, every 4 wks, and end of treatment. MAF changes from BL to wk 4 were characterized as decreased (decrease in ESR1 MAF or none detected [ND]), increased (increase in MAF), or equivocal (in polyclonal patients [>1 mutESR1] with some MAF increasing and decreasing trends). Correlations of MAF change at 4 wks with CB at 24 wks were explored. Results: 29 patients (median of 2 prior metastatic therapies: 97% CDK4/6i, 79% fulvestrant, 48% chemotherapy) had BL mutESR1 of Y537S (66%), D538G (45%), Y537N (28%), and other less frequently detected mutations; 14 (48.3%) patients were polyclonal. 26 of 29 patients had evaluable BL and wk-4 ctDNA results: 21 patients had decreased MAF (81% [54% with ND]), 3 (12%) had increased, and 2 (8%) had equivocal ESR1 MAF changes (Table). CB at 24 wks was seen in 17 patients with a decrease, 2 with an increase, and 1 with equivocal MAF change. A sensitivity of 89.5% and specificity of 20% were calculated for predicting CB based on direction of ESR1 MAF change. The positive predictive value (PPV) for CB with decreased MAF was 81% and the negative predictive value (NPV) for an increased MAF was 33%. Of the 14 (54%) patients with ND ESR1 MAF, 13 had CB resulting in 87% sensitivity, 50% specificity, 93% PPV, and 33% NPV. Conclusion: In ELAINE 2, 81% of patients had decrease/cleared (ND) mutESR1 after 4 wks of LAS plus Abema, which correlated with clinical benefit. All mutESR1 detected appear targeted with this therapy. High sensitivity and favorable PPV were observed in patients with decreased MAF, and even more so in those with ND MAF; however, increased MAF was less specific and not as predictive of treatment failure. Our results indicate that ESR1 liquid biopsy evaluation may be an adequate non-invasive surrogate marker for monitoring patients on treatment. Further study in a larger population of women with endocrine-resistant mBC and acquired mutESR1 is warranted to explore this potential for monitoring treatment response or resistance to this novel LAS-Abema combination. Table. Change from baseline to week 4 in ESR1 MAF and clinical benefit at 24 weeks. CI, confidence interval; MAF, mutant allele fraction; ND, none detected; NPV, negative predictive value; PPV, positive predictive value. *Sensitivity and specificity analyses do not include equivocal results. Citation Format: Senthil Damodaran, Halle Moore, Ciara C. O’Sullivan, Paul V. Plourde, Gary Riordan, Hillary S. Sloane, Debu Tripathy, Dominic Carroll, David J Portman. Estrogen receptor 1 (ESR1) mutations in circulating tumor DNA (ctDNA) from patients with ER+/HER2- metastatic breast cancer (mBC) treated with lasofoxifene plus abemaciclib in the ELAINE 2 study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-05-02.

Abstract Background: The current first-line (1L) standard of care (SOC) for human epidermal growth factor receptor 2-positive (HER2+) metastatic breast cancer (MBC) is trastuzumab (T) plus pertuzumab (P) and a taxane. Despite advances in 1L SOC, most patients (pts) progress during maintenance therapy with T+P. Tucatinib is a tyrosine kinase inhibitor (TKI) approved in combination with T and capecitabine for adults with HER2+ MBC, with and without brain metastases (BM). In HER2CLIMB, the addition of tucatinib significantly prolonged progression-free survival (PFS) and overall survival (OS) in pts with HER2+ MBC and was well tolerated. Adding tucatinib also reduced the risk of disease progression or death in pts with untreated and/or active BM (Murthy et al. 2020, Curigliano et al. 2021). HER2CLIMB-05 investigates whether adding tucatinib to 1L SOC as maintenance therapy will extend PFS while maintaining quality of life (QOL). Methods: HER2CLIMB-05 (NCT05132582) is a phase 3, randomized, double-blind study evaluating tucatinib plus T+P as maintenance therapy for HER2+ MBC. Approximately 650 pts will be enrolled. Eligible pts will have advanced HER2+ disease, no progression on 4–8 cycles of prior 1L SOC, ECOG Performance Status of 0 or 1, and no or asymptomatic BM. Exclusion criteria include prior treatment with anti-HER2 and/or anti-epidermal growth factor receptor TKI (prior SOC for early BC is permitted) or inability to undergo contrast magnetic resonance imaging of the brain. Pts will be randomized 1:1 to receive either tucatinib or placebo twice daily, with T+P once every 21 days. Pts with HR+ disease may receive endocrine therapy. The primary endpoint is investigator-assessed PFS. Secondary endpoints include OS (key endpoint), time to deterioration of health-related QOL, central nervous system PFS, safety, and pharmacokinetic (PK) parameters. PFS and OS will be compared using a 2-sided stratified log-rank test between treatment groups. Time-to-event endpoints will be summarized using the Kaplan–Meier method. PK and safety data will be summarized using descriptive statistics. Enrollment is ongoing in the US, with additional sites planned. Citation Format: Erika Hamilton, Junji Tsurutani, Giuseppe Curigliano, Miguel Martín, Ciara C. O’Sullivan, Joo Hyuk Sohn, Konstantinos Tryfonidis, Libero Santarpia, Shan Yang, Véronique Diéras. Phase 3 study of tucatinib or placebo in combination with trastuzumab and pertuzumab as maintenance therapy for HER2+ metastatic breast cancer (HER2CLIMB-05, trial in progress) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT2-16-03.

Abstract Introduction: We performed matched case-control studies utilizing cohorts of postmenopausal women with ER+ breast cancer receiving adjuvant aromatase inhibitors (AI) on MA.27 [anastrozole, exemestane] or PreFace [letrozole] to assess the association between estrogen suppression after 6 months of treatment and an early breast cancer (EBC) event within 5 years of AI initiation (Clin Cancer Res 2020;26:2986-98). We found a significant 3.0-fold increase in risk of an EBC event for those taking anastrozole with levels of estrone (E1) ≥1.3 pg/mL and estradiol (E2) ≥0.5 pg/mL, but not for exemestane or letrozole. Given these findings we designed a prospective pharmacodynamic (PD) study to evaluate the impact of anastrozole (1 mg/day: ANA1) on E1 and E2 levels, and among those with inadequate estrogen suppression (IES: E1 ≥1.3 pg/mL and E2 ≥0.5 pg/mL), to evaluate the safety and PD efficacy of high-dose anastrozole (10 mg/day: ANA10), which has been found to be safe in prior clinical trials (Cancer 1998;83:1142-52). Methods: Post-menopausal women with stage I-III, ER ≥1% positive/HER2-negative breast cancer who were candidates for anastrozole were eligible after completion of locoregional therapy and chemotherapy, as clinically indicated. Women who were pre-menopausal at diagnosis were not eligible. All patients received 8-10 weeks of ANA1, after which those with adequate estrogen suppression (AES: E1< 1.3 pg/mL or E2< 0.5 pg/mL) came off study. Those with IES went on to receive ANA10 for 8-10 weeks, followed by letrozole (2.5 mg/day: LET) for 8-10 weeks. All patients were managed at their treating oncologist’s discretion following study discontinuation. E1 and E2 blood levels were measured pre-treatment and after completion of each treatment cycle by a CLIA-approved liquid chromatography with tandem mass spectrometry in the Immunochemical Core Laboratory at Mayo Clinic. With a sample size of 29 patients with IES after ANA1, a one-sided binomial test of proportions with a significance level of 0.05 will have an 87% chance of rejecting the proportion with AES after ANA10 is at most 25% (Ho) when the true proportion is at least 50%. Specifically, the null hypothesis is rejected if the number of women with AES after ANA10 is 12 or more. Data lock was July 6, 2022. Results: Of the 161 women enrolled from April 2020 through May 2022, 3 withdrew consent prior to start of ANA1 and 2 were ineligible; thus, 156 women comprised the study cohort. Median patient age was 64 years (range 44-86), 10% of patients were of Hispanic ethnicity and/or non-white race, and 15% received chemotherapy. Six patients remain on ANA1, and 10 discontinued ANA1 due to refusal (7), adverse event (AE) (2), or COVID-19 (1). Forty-one of the remaining 140 patients (29.3%; 95%CI: 21.9-37.6%) had IES with ANA1. Nine of these 41 patients did not go on to ANA10 due to refusal (6) or AE (3). Of the 32 patients who started ANA10, 8 remain on treatment, 5 discontinued due to refusal (3) or AE (1-grade 2 urinary tract infection; 1-grade 1 palpitations), and 19 had a blood draw 45 days or more after starting ANA10. No grade 3-5 AEs or grade 2 hot flashes or arthralgias were reported. Of these 19 patients, 14 achieved AES with ANA10 (73.7%; 95%CI: 48.8-90.9%). All 19 patients switched to LET of which 3 remain on treatment, 1 is missing E1/E2 data, and 15 had a blood draw 45 days or more after starting LET. Of these 15 patients, 10 maintained AES, 2 acquired AES with LET, and 3 no longer had AES. Anastrozole and letrozole drug levels will be reported at the meeting. Conclusions: Approximately 29% of postmenopausal women with ER+/HER2- BC receiving adjuvant anastrozole 1 mg/daily had IES. A majority of these patients achieved AES with dose escalation to ANA10 without tolerability issues. E1 and E2 levels are logical biomarkers given the mechanism of action of anastrozole, and further study utilizing them to determine the optimal dose of anastrozole for a given patient should be performed. Citation Format: Tufia C. Haddad, Vera Suman, Karthik V. Giridhar, Alvaro Moreno-Aspitia, Donald Northfelt, Brenda Ernst, Kostandinos Sideras, Ciara C. O’Sullivan, Ravinder Singh, Zeruesenay Desta, Jodi Taraba, Barbara Goodnature, Matthew P. Goetz, Liewei Wang, James N. Ingle. Anastrozole dose escalation for optimal estrogen suppression in postmenopausal early stage breast cancer: A prospective trial [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT1-04-02.

PURPOSE: For the past 5 years, most major antiemesis guidelines have included olanzapine-containing regimens among the recommended options for prophylaxis with highly emetogenic chemotherapy (HEC). We analyzed the uptake of olanzapine in clinical practice and the changing composition of multidrug antiemetic regimens. METHODS: A retrospective analysis was performed using an OptumLabs deidentified database of medical and pharmacy claims, which was filtered for patients starting HEC in the interval of 2006 to Q2 of 2021. Descriptive statistics were used to analyze patient characteristics and year-by-year antiemetic prescribing patterns, coinciding with cycles 1 and 2 of chemotherapy. RESULTS: A total of 63,154 distinct patients were included. The median age was 58 years (range, 18-88). Breast (45.2%) and hematologic (20.8%) cancers were the most common diagnoses. In 2016, olanzapine was prescribed to 1.4% of patients with cycle 1 of HEC. Prescriptions increased modestly each year, and by 2021, 13.9% of patients received olanzapine with their first cycle of chemotherapy. An additional 5.7% of patients received olanzapine for breakthrough symptoms or enhanced prophylaxis during cycle 2. In 2021, more than three-quarters of patients were prescribed antiemetics in a guideline-concordant manner, with an olanzapine-containing quadruplet (12.2%), an NK1-receptor antagonist triplet (64.5%), or an olanzapine triplet (suppressed for small sample size). CONCLUSION: Despite inclusion in major antiemesis guidelines, there has been relatively slow uptake of olanzapine for prophylaxis with HEC. This finding highlights the challenges of disseminating information and keeping prescribing systems updated with the newest evidence in supportive oncology.

232 Background: Olanzapine has an important role in preventing and treating nausea and vomiting from highly emetogenic chemotherapy (HEC). This drug, for the last 5 years, has been a component of most major antiemesis guidelines. The aim of the current study was to assess how often olanzapine has been prescribed for patients receiving HEC. Methods: A retrospective analysis was performed using an OptumLabs de-identified clinical database of medical and pharmacy claims. The database was filtered for patients starting HEC in the interval of 2006 to Q2 of 2021. Descriptive statistics were used to analyze patient characteristics and year-by-year antiemetic prescribing patterns, coinciding with cycles 1 and 2 of chemotherapy. Results: A total of 63,154 distinct patients were included. The median age was 58 years (range, 18-88). Over a quarter of the patients identified as Black, Hispanic, Asian, or other. Breast (45.2%) and hematologic (20.8%) cancers were the most common diagnoses. In 2016, olanzapine was prescribed to only 1.4% of patients with cycle 1 of HEC. Prescriptions increased modestly each year, and by 2021, 13.9% of patients received olanzapine with their first cycle of chemotherapy. An additional 5.7% of patients received olanzapine for breakthrough symptoms or enhanced prophylaxis during cycle 2. In 2021, over three-quarters of patients were prescribed antiemetics in a guideline concordant manner, with either an olanzapine-containing quadruplet (12.2%), an NK1 receptor antagonist triplet (64.5%), or an olanzapine triplet (exact number suppressed due to small sample size). Conclusions: The rate of olanzapine prescribing is less than might be expected following its inclusion in major antiemesis guidelines. This finding highlights the challenges of disseminating information and keeping prescribing systems updated with the newest evidence in supportive oncology.

Abstract BACKGROUND Breast cancer is one of the most common cancers associated with brain metastases (BM). Up to 50% of patients with metastatic triple-negative breast cancer (TNBC) develop BM which portends a poor prognosis, with a median survival of 4.4-7.3 months. There is a lack of effective systemic therapy. Irinotecan is a topoisomerase-1 inhibitor with a response rate of 5-23% in advanced breast cancer. Nal-IRI is an intravenous liposomal formulation of irinotecan, with greater efficacy in tumor growth inhibition and the ability to cross the blood brain barrier (BBB) than irinotecan, resulting in a prolonged survival in preclinical TNBC BM models. Additionally, Nal-IRI has demonstrated promising anti-tumor activity in patients with TNBC- BM in a phase-I trial (NCT01770353). Pembrolizumab is a humanized anti-PD-1 monoclonal antibody which has shown efficacy in TNBC. The purpose of this study is to evaluate whether the combination of Nal-IRI and pembrolizumab can provide a synergic effect to control the CNS disease and prolong survival in TNBC with progressive BM. METHODS This is a phase II, single arm trial with a safety lead-in to evaluate the efficacy of nal-IRI (50-70mg/m2 IV Q2W) in combination with pembrolizumab (400mg IV Q6W). Simon’s 2-stage design is used, with 18 patients in the 1st stage and additional 24 at 2nd stage for a total of 42. The first 6 patients will serve as a safety lead-in. Key eligibilities include: histologically/cytologically confirmed TNBC with new or progressive BM; prior immunotherapy is allowed but not prior nal-IRI/irinotecan; prior sacituzumab-govitecan is permitted if disease stable for ≥16-week while on therapy and ≥24-week washout prior to starting trial; measurable disease; and ≤4 prior lines of therapy in the metastatic setting. The primary endpoint is CNS disease control rate (DCR) at 6 months using RANO-BM criteria. Secondary endpoints include CNS and non-CNS ORR, PFS and OS. (ClinicalTrials.gov: NCT05255666)

1504 Background: Trial recruitment that requires specific actionable mutations based on next-generation sequencing (NGS) is challenging. Barriers can include competing studies, physician study awareness, site proximity, mutation incidence, among other concerns. Methods: This study (NCT04432454) opened clinical sites using two methods during the COVID-19 pandemic. The “Traditional” approach included site selection, IRB and contract approval, and trial activation prior to a patient being identified for enrollment. The second approach used the Tempus “TIME” Trials network that would only open a site after identifying a patient with a mutation of interest and eligible for the trial. Results: The first patient enrolled was on 10/12/20 and the last patient was on 6/24/21. A total of 16 sites (6 Traditional and 10 TIME) participated. All Traditional sites, and none of the TIME sites, were affiliated with major academic institutions. Duration for full CTA execution for Traditional sites averaged 200.5 days (range 142 to 257) and for TIME sites averaged 7.6 days (range 2 to 14). IRB approval time average for Traditional sites was 27.5 days (range 12 to 71) and TIME sites was 3.0 days (range 1 to 12 days). Days from site selection to activation letter for Traditional sites was on average 250.0 days (range 187 to 281) and for TIME sites was 131.6 days (range 22 to 248). Time from study activation to first consent was 33.3 days (range 18 to 58) for Traditional sites and 8.8 days (range 1 to 35) for TIME sites. The first patient on-study was at a TIME site 115 days prior to a Traditional site and the first 7 patients enrolled were at TIME sites. Traditional sites consented 23 and enrolled 16 patients while the TIME sites consented 16 and enrolled 13. The trial enrolled all 29 patients in 8 months with the anticipated enrollment duration being 12 to 18 months. Conclusions: Although the Traditional and TIME programs had different operational models, they both contributed a significant number of patients and reduced the projected enrollment timeline. TIME sites enrolled the initial patients. These results demonstrate that the “Just-in-Time model,” in conjunction with a Traditional model, can reduce projected overall time to enrollment in biomarker-driven studies. [Table: see text]