Summary

A subset of soft tissue sarcoma (STS) patients achieve significant therapeutic benefit from preoperative radiotherapy (RT). Yet, this treatment paradigm may be associated with limited efficacy and increased toxicity, highlighting the necessity of novel multimodal therapies aimed at local control with few adverse events (AEs). NBTXR3 is a first-in-class Hafnium-Oxide nanoparticle. Designed for cancer cell uptake, it is injected intratumorally (IT) and activated by ionizing radiation to yield a tumor-localized high energy deposit and increased cell death compared to the same dose of RT alone. We report now the first phase II/III randomized clinical trial of NBTXR3 given as preoperative treatment to patients with locally advanced STS of the extremity and trunk wall.

This trial met its primary and secondary endpoints of pCRR and R0 rates, respectively. NBTXR3 with RT demonstrated an acceptable safety profile compared to RT alone. As pCR is a known indicator of long-term treatment response with a positive correlation to both progression free and overall survival, NBTXR3 represent a new option for preoperative treatment for locally advanced STS.

Summary

Purpose: This phase I study assessed the safety of first-in-class radioenhancer nanoparticles, NBTXR3, in elderly or frail patients with locally advanced head and neck squamous cell carcinoma (HNSCC), ineligible for chemoradiation.

Methods: Patients with stage III or IVA (American Joint Committee on Cancer (AJCC) guidelines, 7th edition, 2010) HNSCC of the oral cavity or oropharynx, aged ≥70 or ≥65 years and ineligible to receive cisplatin, amenable to radiotherapy (RT) with curative intent, received NBTXR3 as a single intratumoural (IT) injection followed by activation by intensity-modulated radiation therapy (IMRT; 70 Gy). The NBTXR3 dose corresponded to a percentage of the baseline tumour volume, measured by magnetic resonance imaging. The primary objectives were to determine the recommended phase II dose (RP2D), dose-limiting toxicities (DLTs) and maximum tolerated dose (MTD). Safety and tolerability were assessed using National Cancer Institute CTCAE version 4.0. Antitumour activity was assessed by Response Evaluation Criteria in Solid Tumours 1.1.

Results: Nineteen patients were enrolled: 3 at the dose level of 5%, 3 at the dose level of 10%, 5 at the dose level of 15% and 8 at the dose level of 22% of the tumour volume. The MTD was not reached, and no DLTs or serious adverse event (SAEs) related to NBTXR3 were observed. Four adverse events related to NBTXR3 and/or the IT injection were reported (grade I–II). NBTXR3 remained in the injected tumour throughout RT, with no leakage in the surrounding healthy tissues. Specific RT-related toxicity was as expected with IMRT. The RP2D was determined as 22% baseline tumour volume. Preliminary signs of antitumour activity were observed.

Conclusion: Intratumoural injection of NBTXR3 followed by IMRT is feasible and demonstrated a good safety profile, supporting further evaluation at the RP2D in this patient population.