(0646) Feasibility and Safety of 111In-Panitumumab for Detection of Head and Neck Squamous Cell Carcinoma

Introduction: Determining metastasis in head and neck squamous cell carcinoma (HNSCC) is vital for accurate staging, however, clinical options for doing so have limitations. In this study, we evaluate a tumor-specific approach through a systemically administered radiotracer targeting epidermal growth factor receptor (EGFR) to detect metastatic lymph nodes intraoperatively.

Methods: Between June 2023 and December 2023, 6 patients were enrolled in ongoing clinical trials at Vanderbilt University Medical Center (NCT05901545, NCT05945875). Patients with primary or recurrent HNSCC of any subsite scheduled to undergo surgical resection were eligible. Enrolled patients received an IV loading dose of panitumumab (50 or 100 mg) followed by an IV bolus injection of 5 mCi 111In-panitumumab 1-5 days prior to surgery. A SPECT/CT scan was performed between infusion and surgery. Intraoperatively, 111In-panitumumab within the primary tumor and lymph nodes was detected using a gamma probe. Gamma counts were recorded ex vivo following standard of care neck dissection. The ability of 111In-panitumumab to identify metastatic lymph nodes was assessed via comparison to histopathology. Outcome measures included safety and feasibility. Preliminary analysis were performed using the Mann-Whitney U test.

Results: To date, we have evaluated a total of 6 patients. The primary tumor site was visualized on SPECT/CT imaging and had a median gamma count of 746 suggesting successful targeting of the agent. There were a total of 165 (97.6%) benign lymph nodes with a mean gamma count of 17, whereas tumor-positive lymph nodes had 5.6-fold increase in gamma counts with a mean of 96 (p < 0.001). There have been no adverse events related to the study drug with all patients completing the study.

Conclusions: We identified 111In-panitumumab as a safe and feasible method for detection of metastatic lymph nodes intra-operatively. Future directions of this ongoing clinical trial include optimization of the dose and timing of imaging and surgery after radiotracer injection.