The value of lymph node ultrasound and whole body 18F-FDG PET/CT in stage IIB/C melanoma patients prior to SLNB.

Abstract Background Stage IIB/IIC (8th AJCC) melanoma patients are known to have high-risk primary tumors, however they follow the same routine to sentinel lymph node biopsy (SLNB) as more low risk tumors. Guidelines are not conclusive regarding the use of preoperative imaging for these patients. The aim of this pilot study was to assess the value of ultrasound (US) and 18F-FDG PET/CT prior to lymphoscintigraphy (LSG) and SLNB for stage IIB/C melanoma patients. Methods From 2019-04 till 2020–01, all stage IIB/C melanoma patients underwent US of the regional lymph nodes and whole body 18F-FDG PET/CT before their planned LSG and SLNB. Suspected metastases were confirmed with fine needle aspiration (FNA), prior to surgery. Results In total 23 patients were screened: six had metastases detected by imaging, two by US, one by 18F-FDG PET/CT and three were detected by both imaging modalities. All metastases were nodal and therefore treatment was altered to lymph node dissection and all but one also received adjuvant therapy. Eight (47%) of the 17 patients without macroscopic disease, still had a positive SN. Sensitivity, specificity and false negative rate for US and 18F-FDG PET/CT were 36%, 89%, 64% and 29%, 100% and 71%, respectively. Conclusion Preoperative negative imaging does not exclude the presence of SN metastases, therefore SLNB cannot be foregone. However, US detected metastases in 22% of patients, altering their treatment, which suggests it is effective in the work-up of stage IIB/C melanoma. Staging with 18F-FDG PET/CT is not of added value prior to LSG and SLNB and should therefore not be used.