Comparative Accuracy of 18-Gauge versus 20-Gauge Ultrasound-Guided Fine-Needle Aspiration in the Detection of Persistent Lymph Node Metastasis in Head and Neck Squamous Cell Carcinoma after Chemoradiation

Viable malignant disease is uncommon in patients with persistent adenopathy after definitive chemoradiotherapy (CRT) for head & neck squamous cell carcinoma (HNSCC). Preoperative ultrasound-guided fine needle aspiration (USFNA) can prevent unnecessary neck dissection. Post-radiation fibrosis can complicate the approach, resulting in an inadequate aspirate volume when using standard 20 or 22-gauge needles. We assessed the comparative 18 and 20-gauge diagnostic accuracy of USFNA in detecting persistent viable nodal malignancy in patients with HNSCC with nodal metastasis treated with CRT. We hypothesized that 18-gauge USFNA would outperform 20-gauge USFNA in diagnostic accuracy and efficiency. We identified a 239-patient cohort (210 males, 60.4±9.8 y) presenting between 2002-2023 with HNSCC and biopsy-proven cervical nodal metastases. All patients were treated with CRT. After CRT, a suspicious nodal remnant underwent biopsy with an 18 or 20-gauge needle. 101 patients received a biopsy with a 20-gauge and 138 received a biopsy with an 18-gauge needle. Biopsy results were compared to either post-biopsy surgical pathology results when available or at least 3 months of computed tomography (CT) follow-up, referred to here as post-USFNA results. FNA in 181/239 (75.7%) cases showed no evidence of viable metastatic disease on cytology evaluation. 20-gauge cases were performed with 1.36±0.52 passes. 18-gauge cases were performed with 1.26±0.51 passes (p=0.037). A neck dissection was performed within 90 days in 45 patients, while the other 194 patients had follow-up imaging. 40/58 cases were positive concordant (PC) between FNA and post-USFNA results. 177/181 cases were negative concordant (NC) between FNA and post-USFNA results. Overall, USFNA showed a sensitivity of 90.9%, specificity of 90.8%, accuracy of 90.8%, positive predictive value (PPV) of 69.0% and negative predictive value (NPV) of 97.8%. 20-gauge FNA showed PC of 26/39 and NC of 59/62 for a sensitivity of 89.7%, specificity of 81.9%, accuracy of 84.2%, PPV of 66.7% and NPV of 95.2%.18-gauge FNA showed a PC of 14/19 and NC of 118/119 for a sensitivity of 93.3%, specificity of 95.9%, accuracy of 95.7%, PPV of 73.7% and NPV of 99.2%. Residual cervical lymph node USFNA after CRT is an accurate procedure with excellent PPV and NPV. 18-gauge USFNA is associated with statistically significant fewer biopsy passes and higher specificity compared to 20-gauge. CRT＝chemoradiotherapy; FNA = fine needle aspiration; HNSCC＝ head & neck squamous cell carcinoma; HPV = human papillomavirus; NC = negative concordant; NPV = negative predictive value; PC = positive concordant; PPV = positive predictive value; SND = salvage neck dissection; USFNA = ultrasound-guided fine needle aspiration.