Tawfik, Bernard

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 .

666 Background: In the phase 3 CABINET trial (NCT03375320), cabozantinib (CABO) significantly prolonged median progression-free survival (PFS) compared to placebo (PB) in patients with advanced, previously treated, progressive extrapancreatic NET (epNET) [HR 0.38 (95% CI, 0.25-0.59, P<0.0001)] and pancreatic NET (pNET) [HR 0.23 (95% CI, 0.12-0.42, P<0.0001)] (Chan et al., NEJM, 2024). In this analysis, we focus on outcomes of patients with epNET arising in the GI tract. Methods: Patients with locally advanced or metastatic epNET or pNET were randomized 2:1 in separate cohorts to receive CABO 60 mg daily vs PB. The epNET cohort included patients with tumors arising in the GI tract (not including pancreas), lung, unknown primary, and other rare primary sites. In this subgroup analysis of the epNET cohort, patients with GI NET were included. Eligibility included progression by RECIST within 12 months (mo) prior to registration, ≥ 1 prior systemic therapy. Primary endpoint: PFS by blinded independent central review (BICR). Secondary endpoints: objective response rate, overall survival, safety. Results: 116 of the 203 patients in the epNET cohort had GI NET (CABO, n=70; PB, n=46). Median age was 66 yrs; females: 46%; G1/G2/G3/unknown grade: 35%/57%/6%/2%. ECOG performance status: 0/1-2: 43%/57%. White race: 86%. The most common primary tumor locations were ileum/cecum (54%), small intestine with location not specified (20%); non-cecum colon or rectum (11%), stomach (4%); duodenum (3%); jejunum and nonspecified midgut site (3% each). Prior systemic therapies included somatostatin analogs (SSA) (100%), everolimus (59%); Lu-177 dotatate (77%); temozolomide +/- capecitabine (16%). In patients with GI NET, CABO was associated with improved PFS by BICR compared to PB (stratified HR, 0.50; 95% CI: 0.28-0.88, 1-sided stratified log-rank P=0.007). Median PFS with cabozantinib was 8.5 mo (95% CI, 6.0-16.7) compared to 5.6 mo (95% CI, 3.9-11.0) with PB. CABO demonstrated potential benefit in patients with midgut GI NET and across clinical factors including grade, functional status related to hormone secretion, concurrent SSA use, and prior therapy with Lu-177 dotatate or everolimus. The most frequent grade 3/4 adverse events attributed to therapy with CABO included hypertension (19%), diarrhea (13%), fatigue (10%). Conclusions: CABO is associated with improvement in PFS compared to PB in patients with advanced GI NET. Potential benefit was observed across clinical factors including grade, functional status, concurrent SSA, and prior treatment. The safety profile for CABO in patients with GI NET is consistent with that previously reported. Support: U10CA180821, U10CA180882; U10CA180820 (ECOG-ACRIN), U10CA180868 (NRG Oncology), U10CA180888 (SWOG); Exelixis; https://acknowledgments.alliancefound.org . Clinical trial information: NCT03375320 .