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PURPOSE STELLAR (ClinicalTrials.gov identifier: NCT02796261 ) was a phase III, randomized, open-label trial of eflornithine + lomustine versus lomustine monotherapy in patients with recurrent grade 3 astrocytoma. METHODS At trial initiation, eligibility criteria included: age ≥18 years, anaplastic astrocytoma (2016 WHO CNS Tumor classification [WHO CNS4]), first recurrence ≥6 months after radiation and temozolomide (TMZ), Karnofsky performance status ≥70, and no imaging findings consistent with grade 4 glioblastoma. Random assignment (1:1) was stratified by isocitrate dehydrogenase ( IDH ) mutation, age, resection extent, and geography. Patients received eflornithine (2.8 g/m 2 orally, every 8 hours [2 weeks on, 1 week off]) + lomustine (90 mg/m 2 orally, once every 6 weeks), or lomustine monotherapy (110 mg/m 2 once every 6 weeks). The primary end point was overall survival (OS). RESULTS Among 343 patients randomly assigned across 74 sites in eight countries, there was no difference in survival between eflornithine + lomustine and lomustine monotherapy (median OS 23.4 v 20.3 months, hazard ratio [HR], 0.94). Following changes in classification and grading in the 2021 WHO CNS5, a subset analysis of patients with IDH- mutant, grade 3 astrocytoma (n = 196), defined in 2024, before unblinding, showed clinically meaningful improvements in median OS with eflornithine + lomustine versus lomustine monotherapy (34.9 v 23.5 months, HR, 0.64) and median progression-free survival (PFS, 15.8 v 7.2 months, HR, 0.57). No differences were observed among patients with CNS grade 4 disease. Grade ≥3 treatment-emergent adverse events of relevance were related to reversible myelosuppression (eflornithine + lomustine 42% v lomustine monotherapy 29% of patients) and hearing impairment (24% v 0%). No new safety signals were identified. CONCLUSION Clinically meaningful improvements were observed; eflornithine + lomustine doubled PFS and improved OS in patients with recurrent IDH -mutant, grade 3 astrocytoma, but not grade 4 tumors, after prior radiotherapy and TMZ, consistent with its cytostatic mechanism of action.

Abstract BACKGROUND STELLAR was a phase III randomized, open-label trial of eflornithine (ornithine decarboxylase inhibitor) with lomustine versus lomustine alone in patients with recurrent anaplastic astrocytoma (AA). We previously reported an overall survival (OS) and progression free survival (PFS) of the combination in the patients with grade 3 IDH-mutant astrocytoma. Here we report updated OS and PFS outcomes based on additional molecular classification and blinded independent central review (BICR). METHOD Eligibility included: age ≥ 18 years, AA (2016 WHO criteria) with first recurrence ≥ 6 months after radiation, KPS ≥ 70, and no imaging findings consistent with grade 4 glioblastoma. Patients received eflornithine (2.8 g/m2 TID Q 2/3 weeks) with lomustine (90 mg/m2 Q 6 weeks) (Arm A) or lomustine alone (110 mg/m2 Q 6 weeks) (Arm B). Primary endpoint was OS. RESULTS Updated molecular data resulted in re-classification of the 343 AA patients enrolled into 3 WHO 2021 defined tumor subtypes, 196 tumors were IDHmut, CDKN2A/B intact, consistent with diagnosis of astrocytoma, IDHmut, WHO grade 3, 33 tumors had CDKN2A/B loss consistent with astrocytoma, IDHmut, WHO grade 4, 106 tumors were IDHwt consistent with diagnosis of glioblastoma, IDHwt, WHO grade 4. Updated results strengthen initial conclusion that eflornithine plus lomustine resulted in significant survival benefit in the astrocytoma, IDHmut, WHO grade 3 group (mOS 34.9 vs, 23.5 months, HR = 0.64, stratified log rank p =0.0136). PFS with eflornithine was also improved (15.8 vs, 7.2 months, HR = 0.57, stratified log rank p =0.0113). BICR demonstrated a high correlation between investigator and centrally determined PFS (p=0.0305), and high correlation between OS and PFS (p=.0001). CONCLUSION The clinically meaningful OS and PFS benefits observed with eflornithine in the molecularly defined 2021 WHO CNS grade 3 astrocytomas is further confirmed and expanded based on additional molecular classification and BICR of PFS.

Abstract BACKGROUND Recurrent anaplastic astrocytoma (AA), a grade 3 brain cancer, remains an unmet medical need. STELLAR was a phase III randomized, open-label trial of eflornithine (ornithine decarboxylase inhibitor) with lomustine versus lomustine alone, originally for patients with recurrent AA. However, as the WHO definition of AA evolved during trial conduct (e.g., excluding IDH wild-type disease), we determined results in both the original ITT population and by revised molecularly defined WHO 2021 diagnoses in pre-planned analyses. METHOD Key eligibility: age ≥ 18, AA (2016 WHO criteria), first recurrence ≥ 6 months after radiation and temozolomide, KPS ≥ 70, no imaging findings consistent with grade 4 glioblastoma. Stratification: IDH, age, resection extent, and geography. Patients were randomized to Arm A: eflornithine (2.8 g/m2 TID Q 2/3 weeks) with lomustine (90 mg/m2 Q 6 weeks) or Arm B: lomustine (110 mg/m2 Q 6 weeks). Primary endpoint was OS. The pre-specified hazard ratio (HR) goal was 0.667 based on projected median OS (mOS) increase to 18 months from 12 months. RESULTS 343 pts (172/171 Arms A/B) were randomized (105 sites, 8 countries). ITT analysis found no difference between arms (mOS 23.4 vs. 20.3 months, HR = 0.94). However, a pre-specified subset analysis in IDH mutant, 2021 WHO-defined grade 3 astrocytoma (n=194), showed significant improvement with eflornithine (mOS 34.9 vs. 23.5 months, HR = 0.64, log rank p = 0.016) and PFS (15.8 vs. 7.2 months, HR = 0.58, log rank p = 0.015). No difference was observed in the IDH wild-type subset. AEs were consistent with historic data. CONCLUSION There was no difference in OS between arms in the ITT analysis. However, medically meaningful and statistically significant OS and PFS benefits were observed with eflornithine in the pre-planned analysis of patients with molecularly defined 2021 WHO CNS grade 3 astrocytoma.

Abstract BACKGROUND Patients with meningiomas that have progressed after surgery and/or radiation have limited treatments. Loss of NF2 and CDKN2A/B are common in higher-grade meningiomas and promote meningioma progression. We evaluated the efficacy of abemaciclib, a cyclin-dependent kinase (CDK) 4/6 inhibitor, as part of Alliance A071401, a genomically-driven phase II trial in recurrent or progressive meningiomas. METHODS Eligible patients (pts) with grade 2/3 tumors and NF2 mutations or CDK pathway alterations were treated with abemaciclib 200 mg orally twice daily. Two co-primary endpoints were used: progression-free survival at 6 months (PFS6) and response rate (RR); the trial would be declared positive if either endpoint was met. Twenty-four evaluable pts provided ≥85% power to detect a PFS6 ≥41.5% (vs. null 15%; alpha=0.02), and ≥89% power to detect RR ≥20% (vs. null 2.5%; alpha=0.021). RESULTS Of 83 pts screened while the abemaciclib arm was open between September 15, 2021 and October 3, 2022, 36 eligible pts received abemaciclib. The observed PFS6 rate in the first 24 evaluable pts was 54% (95% CI 33-75%), thus the study met PFS6 endpoint. Of all 35 evaluable pts, median PFS was 7.6 months (95% CI 3.6-17.1 months), estimated 6-month PFS was 55% (95% CI 40-75%) and estimated 6-month OS was 88% (95% CI 77-100%). No objective responses were observed. Of the 36 pts who started treatment, two had a grade 4 adverse event at least possibly related to treatment which included ALT elevation(1), AST elevation(1) and vomiting(1). Patients with NF2 alterations (n=24) had favorable PFS6 outcomes (58%, 95% CI 37-78%) compared to those with CDK (n=4, 25%, 95% CI 1-81%) and CDK+NF2 alterations (n=7, 29% 95% CI 4-71%), (Fisher’s Exact p=0.036). CONCLUSIONS Abemaciclib was well-tolerated and resulted in improved PFS6, meeting the trial’s co-primary endpoint. Abemaciclib warrants further investigation for the treatment of patients with progressive meningiomas.

2001 Background: Systemic treatments are limited for patients with meningiomas that have progressed after surgery and/or radiation. Loss of NF2and CDKN2A/Bare common in higher grade meningiomas and promote meningioma progression in preclinical models. We evaluated the efficacy of abemaciclib, a cyclin-dependent kinase (CDK) 4/6 inhibitor, as part of Alliance umbrella trial A071401, a genomically driven phase II study in recurrent or progressive meningiomas. Methods: Eligible patients (pts) with grade 2/3 tumors and NF2 mutations or CDK pathway alterations were treated with abemaciclib 200 mg orally twice daily until progressive disease. Two co-primary endpoints were used: progression-free survival at 6 months (PFS6) and response rate (RR) by Macdonald criteria; the trial would be declared positive if either endpoint was met. Twenty-four evaluable pts provided >85% power to detect a PFS6 >41.5% (vs. null 15%; alpha =0.02). The threshold for promising results for PFS6 was 8+/24 pts. For RR, 24 evaluable pts provided >89% power to detect RR >20% (vs. null 2.5%; alpha = 0.021). The threshold for promising results for RR was 3+/24 pts. Results: Of 83 pts screened while the abemaciclib arm was open between September 15, 2021 and October 3, 2022, 36 eligible pts received treatment. The mean number of treatment cycles administered was 7 and median follow-up since start of treatment was 11 months. The first 24 pts that met eligibility criteria and began treatment were considered evaluable for the primary endpoint analysis. Of the 24 pts evaluated, 58% were female and the median age was 62 years. The observed PFS6 rate was 54% (13/24 pts, 95% confidence interval 33-75%), thus the study met PFS6 endpoint. No objective responses were observed. Of the 36 pts who started treatment, eight had a grade 3 and two had a grade 4 adverse event at least possibly related to treatment. Grade 3 toxicities included anemia (2), neutropenia (2), leukopenia (1), blurry vision (1), diarrhea (2), fatigue (2), ALT elevation (1), dehydration (1), hyperkalemia (1), hyponatremia (1), dizziness (1), acute kidney injury (1), and thromboembolic event (1). Grade 4 toxicities included ALT elevation (1), AST elevation (1) and vomiting (1). Conclusions: Abemaciclib was well tolerated and resulted in an improved PFS6. The overall trial endpoint was met. Abemaciclib warrants further investigation for the treatment of patients with progressive grade 2/3 meningiomas. Support: U10CA180821, U10CA180882; UG1CA189867 (NRG Oncology); Eli Lilly; https://acknowledgments.alliancefound.org . Clinical trial information: NCT02523014 .

Background Pituitary carcinoma (PC) is an aggressive neuroendocrine tumor diagnosed when a pituitary adenoma (PA) becomes metastatic. PCs are typically resistant to therapy and develop multiple recurrences despite surgery, radiotherapy and chemotherapy. Recently, treatment with temozolomide (TMZ) has shown promising results, although the lack of prospective trials limits assessment of benefit. Methods We describe a single-center multidisciplinary experience in managing PC patients over a 22-year period and review previously published PC series. Results Seventeen patients were identified. Median age at PC diagnosis was 44 years (range 16–82 years), and the median time from PA to PC transformation was 5 years (range 1–29 years). Median follow-up time was 28 months. Most PCs were hormone-positive (n = 12): ACTH (n = 5), PRL (n = 4), LH/FSH (n = 2) and GH (n = 1). All patients underwent at least one resection and at least one course of radiation after PC diagnosis. Immunohistochemistry showed high Ki-67 labeling index (>3%) in 10/15 cases. Eight patients (47%) had only central nervous system (CNS) metastases; six (35%) had combined CNS and systemic metastases. The most commonly used chemotherapy was TMZ, and TMZ-based therapy was associated with the longest PFS in 12 (71%) cases, as well as the longest period from PC diagnosis to first progression (median 30 months). The 2, 3 and 5-year survival rate of the entire cohort was 71, 59 and 35%, respectively. All patients surviving >5 years had been treated with TMZ-based therapy. Conclusions PC management benefits from multidisciplinary care and multimodality therapy. TMZ-based regimens were associated with high survival rates and long disease control.

2068 Background: Pituitary carcinoma (PC) is a rare and aggressive neuroendocrine tumor diagnosed once a pituitary adenoma (PA) becomes metastatic. Although no standard treatment currently exists, surgery, radiation (XRT) and/or chemotherapy are most commonly used. Recently, treatment with temozolomide (TMZ) has shown promising results, although the lack of prospective trials limits accurate outcome assessment. Methods: We describe a single-center multidisciplinary team experience in managing PC patients over a 13-year period (Oct, 2003 to Jan, 2017). Results: A total of 17 patients (9 males) were seen. Median age at diagnosis of PC was 44 years (range 16-82 years) and the median time from PA to PC conversion was 6 years (range 1-29 years). Median follow-up time: 28 months (range 8-158 months) with 7 reported deaths. The majority of PC was hormone-secreting (HS) subtype (n = 12): ACTH (n = 5), PRL (n = 4), FSH/LH (n = 2), GH (n = 1). After PC diagnosis, all pituitary tumors were locally invasive, all underwent at least one resection (mean 2.3) and all received at least one course of XRT alone (IMRT = 76%, SRS = 29%, IMPT = 12%) or concurrent with chemotherapy (18%). Immunohistochemistry showed high Ki-67 labeling index ( > 3%) in 9 (53%) cases. Most cases (n = 14) had metastases to the CNS, 35% of those had combined CNS and systemic foci. Ten (59%) cases underwent focal treatment of metastases, 90% of which underwent XRT. The most common chemotherapy used was TMZ [n = 14 (82%): single agent (n = 10); TMZ+capecitabine (n = 5); concurrent TMZ+XRT (n = 3); concurrent TMZ+XRT with adjuvant TMZ (n = 1)]. The median longest progression-free survival (LPFS) was 18 months (range 4-45 months). TMZ was associated with the chemotherapy-related LPFS in 9 (75%) cases. The 2, 3 and 5 year survival rate was 65%, 53% and 35%, respectively. All patients surviving > 5 years were treated with TMZ (n = 5, 2 survived > 10 years). Two refractory cases are currently on PD-1 inhibitor agent. Eighty percent of non-functioning PC were alive at last follow-up (HS-PC, 58%). Recurrence occurred in 11 (65%) cases. Conclusions: Treatment of PC requires a multidisciplinary approach. Multimodality therapy with surgery, radiation and TMZ was associated with higher survival rates and longer PFS.