Glycoprotein Nonmetastatic Melanoma Protein B as Potential Imaging Marker in Posttherapeutic Metastatic Head and Neck Cancer

OBJECTIVE: To evaluate expression of potential molecular imaging targets epidermal growth factor receptor (EGFR), glycoprotein nonmetastatic melanoma protein B (GPNMB), and vascular endothelial growth factor (VEGF) in lymph nodes (LNs) with or without head and neck squamous cell carcinoma (HNSCC) metastases after (chemo)radiation. STUDY DESIGN: Retrospective study comparing receptor expression in paired lymph nodes after initial treatment. SETTING: A tertiary referral hospital. SUBJECTS AND METHODS: Salvage neck dissection specimens of 40 patients treated with (chemo)radiation were selected. LNs that contained viable tumor, reactive changes after initial treatment, and normal LNs were analyzed using immunohistochemically determined H-scores and by calculating sensitivity and specificity rates and positive/negative predictive values (PPVs/NPVs). RESULTS: EGFR expression was found in 86% and GPNMB expression in 100% of the LNs with viable tumor. VEGF expression was present in all lymph node types. For EGFR, the sensitivity rate was 86%, and specificity rate was 81%. For GPNMB, these were 100% and 75%, respectively. PPV of EGFR was 61.8% and NPV was 98.2%. These were 56.4% and 100% for GPNMB, respectively. CONCLUSION: In residual or recurrent HNSCC lymph node metastases, both EGFR and GPNMB show tumor-specific expression in immunohistochemistry, which may prove useful in future molecular imaging in salvage neck dissections. Immunohistochemically detected VEGF expression indicates that this target is not feasible for imaging purposes in salvage surgery. Therefore, GPNMB could be a new potential imaging target showing comparable results to EGFR in immunohistochemistry.