JNJ-90301900 (NBTXR3) Activated by Radiotherapy With or Without Cetuximab in LA-HNSCC

This is a global, open-label, randomized, 2-arm, Investigator's choice Phase 3 (Pivotal Stage) study to investigate the efficacy and safety of JNJ-90301900 (NBTXR3) / radiation therapy (RT)±cetuximab versus RT±cetuximab in treatment-naïve, platinum-ineligible, elderly participants with locally advanced head and neck squamous cell carcinoma (LA-HNSCC).

Participants will undergo a screening assessment over a period of less than or equal to (\<=) 28 days to determine eligibility.

Eligible participants will be treated by the Investigator's choice of RT alone or RT in combination with cetuximab. Following the Investigator's choice, participants will be randomized in a 1:1 ratio:

* Arm A: JNJ-90301900 (NBTXR3), as an intratumoral/intranodal injection, activated by investigator's choice of RT alone or RT in combination with cetuximab
* Arm B: Investigator's choice of RT alone or RT in combination with cetuximab

All participants (Arm A and Arm B) will receive 70 Gy in 35 fractions over a 7 week period.

An EOT visit will be performed 4 weeks after the completion of RT. Follow-up visits will start at 12 weeks post-RT completion, and will continue every 12 weeks for 2 years, and then every 24 weeks thereafter until death; the participant is determined to be lost to follow up; withdrawal of consent; or the end of the study, whichever occurs first. Participants who have received further anti-cancer therapy for the study disease and/or have had disease progression/recurrence will be followed only for survival information

Eligibility Criteria:
Inclusion Criteria:

* Age greater than or equal to (\>=) 60 years old
* Squamous cell carcinoma of the oral cavity, oropharynx, hypopharynx, or supraglottic larynx and a candidate for definitive radiation therapy with or without cetuximab
* Clinical stage T3-4 NX or T2 N2-3 disease according to the 8th edition of AJCC
* One primary tumor lesion amendable for intratumoral injection
* Ineligible to receive platinum-based chemotherapy with radiation (at least one of the following):

  1. Estimated creatinine clearance \>= 30 and less than (\<) 50 milliliters/minute (mL/min) (per Cockcroft-Gault equation), Grade \>= 2 hearing loss or tinnitus, Grade \>= 2 peripheral neuropathy, Eastern Cooperative Oncology Group (ECOG) Performance Status 2 or New York Heart Association Class 3
  2. Age 70-74 years old with Geriatric 8 (G8) score less than or equal to (\<=) 14
  3. Age \>= 75 years old

Exclusion Criteria:

* Carcinoma of the nasopharynx, paranasal sinus(es), salivary gland, thyroid gland, or unknown primary
* Non-squamous cell histology
* Clinical stage T1-2 N0, T2 N1, or M1 disease according to the 8th edition of AJCC
* Loco-regionally recurrent head \& neck cancer that has been previously treated with surgery, radiation therapy, and/or chemotherapy
* Prior or concurrent primary malignancy (including second synchronous head \& neck cancer) within the last 2 years of informed consent and whose natural history has the potential to interfere with the safety and efficacy assessment of the investigational agent
* Ongoing or active infection requiring treatment with antimicrobial therapy within 2 weeks of randomization