This clinical trial focuses on patients with a condition known as unknown primary tumor of the head and neck. This means that cancer has spread to the head and neck area, but the original source of the cancer is not known. The study aims to find the primary cancer site using a special technique called targeted fluorescence endoscopy. This method involves using a fluorescent tracer, which is a substance that lights up under certain conditions, to help doctors see the cancer more clearly. In this study, the tracer used is called cetuximab-800CW, which is a modified version of a medication known as Erbitux.

The purpose of the study is to see if this new method can help identify the primary tumor in the upper part of the throat and digestive tract. Participants will undergo a procedure where the fluorescent tracer is given through an intravenous infusion, meaning it is delivered directly into the bloodstream. After the tracer is administered, doctors will use a special camera to look for the glowing areas that might indicate the presence of cancer. This process is expected to help in locating the primary tumor that was not found during standard tests like physical exams, X-rays, or CT scans.

The study will observe how well the tracer works in highlighting cancerous areas and will compare these findings with traditional methods. It will also collect information about the participants, such as their age, sex, and medical history, to understand how these factors might affect the results. The study will also assess the quality of life of participants before and after the procedure to ensure their well-being. The trial is expected to continue until the end of 2026, with the aim of improving the detection of primary tumors in patients with this challenging condition.