LAUSR

332 Background: Pts with advanced G1/G2 NETs have limited treatment options with overall response rates (ORR) with targeted agents (TA) < 10%. Benefit on PFS after TA therapy has not been demonstrated. The mechanism of action of lenvatinib (VEGFR1-3 & FGFR1-4 inhibitor) may increase efficacy and revert primary and acquired resistance to TA. We report the updated results on PFS, safety and subgroups. Methods: This prospective phase II study had two cohorts: G1/G2 panNETs and giNETs. All pts had baseline documented disease progression (PD) by RECIST. For panNETs, PD to TA was mandatory, regardless prior therapy with somatostatin analogs (SSAs) or chemotherapy (CHT), and for giNETs, PD on SSAs. Pts were treated with lenvatinib at 24 mg qd until PD or intolerable toxicity. The primary endpoint was ORR by central radiology review. PFS was calculated by investigator assessment. Biochemical responses were defined as reduction from baseline > 50%. With 55 pts per arm our study was powered to identify an ORR ≥ 25% (90% power, 5% α-error). Results: We recruited 111 pts (55 panNETs/56 giNETs). Prior therapies were CHT 32%, SSAs 87%, everolimus (E) 70% and sunitinib (S) 30% for panNETs. ORR was 29%, 40% for panNETs and 18.5% for giNETs. With a median follow-up of 17 months (m), PFS for panNETs was 15.8 m (95% CI 11.4-NR) and 15.4 m (95% CI 11.5-19.5) for giNETs. Dose reductions/interruptions were needed in 91.8% with a median dose of 20 mg qd. In the subgroups analyses, all pts obtained the same benefit in PFS and ORR, including grade and prior therapy with S (PFS: 16.4 m, ORR: 43.7%) or E (PFS: 15 m, ORR: 37.1%) (p = ns). A significant correlation of chromogranin A decrease and prolonged PFS in giNETs (17.6 m vs NR, p = 0.032) was observed. The most frequent G3-4 adverse events were hypertension (20.7%), asthenia (13.5%), diarrhea (7.2%) and abdominal pain (5.4%). Conclusions: Lenvatinib showed the highest reported ORR with a TA by central radiology assessment in panNETs and giNETs with promising PFS in a pretreated population. The benefit was observed across subgroups analyses, including pretreated pts with TA. Clinical trial information: NCT02678780.