This study is exploring a new treatment for elderly patients with **locally advanced head and neck squamous cell carcinoma (LA-HNSCC)**. **Squamous cell carcinoma** is a type of cancer that affects certain tissues in the head and neck. Participants are given a choice of radiation (RT) alone or with a drug called cetuximab, which helps treat cancer. Participants are randomly divided into two groups: one receives an injection of a drug called **JNJ-90301900 (NBTXR3)** with their chosen treatment, and the other receives their chosen treatment without the injection. The study lasts for a minimum of 7 weeks of treatment, with follow-up visits every 12 weeks for two years, then every 24 weeks, to check on participants' health. This includes a final visit four weeks after treatment ends. **Key Points:** - The study involves a 7-week treatment period with follow-ups every 12 weeks for 2 years. - Participants must be 60 years or older and have certain types of head and neck cancer. - The study compares two treatments: one with and one without the new drug JNJ-90301900 (NBTXR3).