Geyer, Susan Michelle

TPS2103 Background: Treatment for newly diagnosed IDH-mutant astrocytoma, WHO grade 3, is based on the results of the CATNON study, demonstrating benefit of radiotherapy followed by 12 months of adjuvant temozolomide. While temozolomide and radiotherapy significantly improved survival, the prognosis for these patients remains limited and more effective therapies are required. This trial will evaluate the benefit of the addition of the IDH1 and IDH-2 inhibitor vorasidenib to adjuvant temozolomide versus placebo following standard radiotherapy to evaluate possible improvement in outcomes. Methods: Alliance A072301 (NCT07215910) is a multicenter, double-blinded phase 3 randomized study to determine if the addition of vorasidenib to adjuvant temozolomide significantly improves progression-free survival (PFS), based on blinded central review in patients with newly diagnosed, IDH-mutant astrocytoma, WHO grade 3. Key inclusion criteria include age ≥ 12 years old, histological confirmation of astrocytoma (absence of 1p/19q codeletion), WHO grade 3, presence of any IDH mutation, plan for radiation and chemotherapy and surgery within 6 months. The presence of CDKN2A/B homozygous deletion, spinal or leptomeningeal disease, as well as prior chemotherapy, cranial irradiation or IDH inhibitor therapy, is exclusionary. 408 patients will be randomized 1:1 to receive vorasidenib 40 mg or placebo daily with 12 cycles of temozolomide following radiotherapy and then continued as monotherapy until disease progression or unacceptable toxicity. Stratification factors include age (< 40 years old vs ≥ 40 years old) and residual disease (< 2 cm vs ≥ 2 cm). Tumor assessments with MRI will be every three months for the first two years, every four months for the next two years and then every six months thereafter as per blinded independent central review using the Response Assessment in Neuro-Oncology (RANO) 2.0 criteria. Key secondary endpoints include PFS by local review, time to next treatment, safety and tolerability, quality of life measures. Exploratory measures will include seizure frequency. The trial will have 85% power to detect a hazard ratio of 0.625 with one-sided type I error rate of 0.025. Enrollment for the trial commenced February 2026. Support: U10CA180821, U10CA180882, U24CA196171. https://acknowledgments.alliancefound.org.

4178 Background: In the CABINET trial, CABO significantly prolonged progression-free survival (PFS) compared to placebo (PB) in patients (pts) with advanced, previously treated extrapancreatic NET (epNET) or pancreatic NET (pNET) (Chan et al., NEJM, 2025). Here we report outcomes according to functional status based on NET hormone secretion. Methods: Pts with locally advanced or metastatic epNET or pNET were randomized 2:1 in separate cohorts to receive CABO 60 mg daily vs PB. Eligibility included progression by RECIST within 12 months (mo) before registration, ≥ 1 prior systemic therapy not including somatostatin analogs (SSA). Pts with functional NET due to hormone secretion and non-functional NET were included. In this post hoc subgroup analysis, we analyzed PFS by blinded independent central review and adverse events for pts receiving CABO vs PB based on functional status. Cox regression models were used with stratification on primary tumor site (epNET vs pNET). Subset analyses to evaluate treatment arm differences were conducted in pts with functional and non-functional tumors. Due to small numbers, separate results for those with unknown functional status are not included. Results: Of the total 298 pts enrolled in both cohorts, 74 had a functional NET (CABO, n = 47; PB, n = 27); 179 had a non-functional NET (CABO, n = 123; PB, n = 56); 45 had unknown functional status (CABO, n = 28; PB, n = 17). For functional NET, primary tumor sites were GI tract (n = 50; 68%), pancreas (n = 15; 20%), unknown (n = 4; 5%), lung (n = 3; 4%), and thymus (n = 2; 3%). Secreted hormones that were reported included serotonin (55%), somatostatin (18%), gastrin (16%), glucagon (4%), insulin (4%), ACTH (1%), and vasoactive intestinal peptide (1%). For non-functional NET, primary tumor sites were pancreas (n = 75; 42%), GI tract (n = 42; 23%), lung (n = 30; 17%), unknown (n = 17; 9%), thymus (n = 8; 4%), and other (n = 7; 4%). Concurrent SSA was received by 91% and 53% of pts with functional and non-functional NET, respectively. In both subgroups, CABO was associated with improved PFS compared to PB (for functional NET: stratified hazard ratio [sHR], 0.40; 95% confidence interval [CI]: 0.20-0.82, P = 0.012; for non-functional NET: sHR, 0.26; 95% CI: 0.17-0.41, P < 0.001). The most frequent grade 3/4 adverse events (AEs) attributed to CABO vs PB in pts with functional NET included hypertension (21% vs 11%), diarrhea (9% vs 11%), and fatigue (2% vs 15%); in pts with non-functional NET, grade 3/4 AEs included hypertension (21% vs 4%) and fatigue (18% vs 4%). Conclusions: Subset analyses of the CABINET trial suggest that CABO is an effective treatment option for pts with functional and non-functional epNET or pNET. Efficacy and safety results for pts with functional or non-functional NET treated with CABO are consistent with results for the entire trial. Clinical trial information: NCT03375320 .