Abstract B002: Phase I study of endoscopic ultrasound (EUS)-guided NBTXR3 delivery activated by radiotherapy (RT) for locally advanced or borderline resectable pancreatic cancer (LAPC or BRPC)
Authors: Fuentes Gabriela , Rodriguez Maria J. , Katz Matthew H.G. , Ikoma Naruhiko , Tzeng Ching-Wei D. , Overman Michael , Pant Shubham , Lee Michael S. , Wolff Robert A. , Javle Milind , Taniguchi Cullen M. , Holliday Emma B. , Ludmir Ethan B. , Das Prajnan , Koong Albert C. , Vivar Omar I. , Liu Suyu , Tamm Eric P. , Farber Leonard A. , Bhutani Manoop S. , Koay Eugene J. 
Published: January 2024

Patients with LAPC or BRPC often receive radiation therapy (RT) after chemotherapy (chemo) if no metastatic progression has occurred. Historically, CA19-9 normalizes in ~20 to 30% of patients after all therapy. While escalated dose radiotherapy (EDR) has shown promising survival in selected patients, extending use of EDR to all patients is challenging due to RT dose limitations of the bowel. To overcome this limitation, we are investigating NBTXR3, composed of functionalized hafnium oxide nanoparticles administered by a single intratumoral injection, locally amplifying the RT dose. In this phase 1 trial, the primary objective is to determine the NBTXR3 recommended phase 2 dose (RP2D). Secondary objectives are to measure anti-tumor effects. The study uses a Bayesian optimal interval design (BOIN) and has two parts: dose-finding (NBTXR3 at [level 1] 33% of gross tumor volume [GTV] or [level 2] at 42% of GTV) and cohort expansion at RP2D. In part 1, eligibility criteria included only LAPC patients with no evidence of metastatic disease after 2-6 months of chemo, part 2 allows BRPC. NBTXR3 was administered once prior to RT via an EUS-guided intratumoral injection. All patients received 45 Gy in 15 fractions with intensity modulated radiation therapy (IMRT). Patients were followed up to 1 year. Dose-limiting toxicities (DLTs) were defined as any grade ≥ 3 adverse events definitely or possibly related to NBTXR3 and/or RT. Target tumor response was per RECIST v1.1 criteria. CA19-9 was measured serially. We defined CA19-9 normalization as a value of 37 U/ml after finishing NBTXR3/RT. We compared rates of CA19-9 normalization in this phase 1 trial to a historical cohort of patients who received modern chemo/RT without NBTXR3. As of July 12, 2023, 15 LAPC patients have been treated with NBTXR3/RT. The median age was 63 years [range 43-81], 8 males, 7 females. The first patient (level 1) and subsequent 14 patients (level 2) had no injection complications. Level 2 had 1 non-serious DLT related to RT. At 4 weeks post RT, 13 had stable disease (SD) locally (2 had progressive disease [PD] overall), 1 had PD locally, and 1 had radiographic complete response (CR). At 3 months post RT, 11 had SD locally (1 PD overall), 1 PD locally, and 1 had surgery with negative margins and no residual viable tumor. 9 patients had elevated CA19-9 before NBTXR3/RT, 7 of these 9 (78%) had a decrease in CA19-9 subsequently, and 2 of these 9 (22%) had CA19-9 normalization eventually. 12 patients had elevated CA19-9 at diagnosis, and 5 out of 12 patients (42%) had normalization of CA19-9 after all therapy. We reviewed 455 patients with LAPC/BRPC between 2015-2019 who were treated at our institution as a comparison cohort for CA19-9 normalization rates. Out of 307 patients with elevated CA19-9 at diagnosis and normal bilirubin, 95 normalized (31%) and 212 did not normalize (69%) within 6 months of receiving cytotoxic therapy. The RP2D of NBTXR3 is 42% of GTV. The responses and CA19-9 results in comparison to historical data suggest promising anti-tumor efficacy of NBTXR3/RT.

Citation Format: Gabriela Fuentes, Maria J. Rodriguez, Matthew H.G. Katz, Naruhiko Ikoma, Ching-Wei D. Tzeng, Michael Overman, Shubham Pant, Michael S. Lee, Robert A. Wolff, Milind Javle, Cullen M. Taniguchi, Emma B. Holliday, Ethan B. Ludmir, Prajnan Das, Albert C. Koong, Omar I. Vivar, Suyu Liu, Eric P. Tamm, Leonard A. Farber, Manoop S. Bhutani, Eugene J. Koay. Phase I study of endoscopic ultrasound (EUS)-guided NBTXR3 delivery activated by radiotherapy (RT) for locally advanced or borderline resectable pancreatic cancer (LAPC or BRPC) [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B002.