Phase I dose-escalation study of NBTXR3 activated by intensity-modulated radiation therapy in elderly patients with locally advanced squamous cell carcinoma of the oral cavity or oropharynx

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.

Trial registration: ClinicalTrials.govNCT01946867.