Schéma : Cancers of the oral cavity represent 30% of head and neck carcinomas in the western world. The oropharynx is the posterior continuation of the oral cavity and connects with the nasopharynx (above) and laryngopharynx (below). It is also a frequent site of primary head and neck cancers. These structures play a crucial role in swallowing, breath and speech. Locally advanced oropharyngeal cancers can obstruct the air flow or infiltrate muscles or nerves, which significantly disturb local functions. The incidence of Head and Neck Squamous Cell Cancer in patients older 65 years is high, 47% occurred in this population as recorded by the Surveillance, Epidemiology, and End Results registries in the United States. Regarding the therapeutic strategies, the association of radiotherapy with chemotherapy or biologics has demonstrated significant improvement of outcomes with the drawback of higher toxicity, or as demonstrated by 2 meta-analyses, without survival improvement in older patients. NBTXR3 and radiation therapy may increase the cancer cell killing and complete tumor shrinkage allowing a definitive treatment and preservation of local structures and functions in patients older 65 years, who cannot receive cisplatin.

Patients will receive a single administration of NBTXR3 on day 1, either as an intra-arterial or intratumor injection, followed by Intensity Modulated Radiation Therapy starting 24 hours later (day 2), and up to completion of 7 weeks, i.e. 70 Grays, 2Grays/fraction. Patients whose tumor has completely shrunk will be followed for the post-radiotherapy evaluation up to the End of Treatment visit. Those patients whose tumor has not shrunk more than 50% of the baseline size, will stop the radiotherapy and may have a salvage tumor surgery. Then, all patients will be followed every 8 weeks, for the safety evaluation and cancer disease status until the end of the study.