Whole-Body Imaging for the Primary Staging of Melanomas-A Single-Center Retrospective Study

Abstract

Background: Melanoma staging at diagnosis predominantly depends on the tumor thickness. Sentinel lymph node biopsy (SLNB) is a common tool for primary staging. However, for tumors of >4 mm with ulceration, 3D whole-body imaging and, in particular, Fluor-18-Deoxyglucose positron emission tomography combined with computed tomography (¹⁸F-FDG-PET/CT), is recommended beforehand. This study aimed to investigate the real-world data of whole-body imaging for initial melanoma staging and its impact on the subsequent diagnostic and therapeutic procedures.

Methods: In this retrospective single-center study, 94 patients receiving ¹⁸F-FDG-PET/CT and six patients with whole-body computed tomography (CT) scans were included. The clinical characteristics, imaging results, and histologic parameters of the primary tumors and metastases were analyzed.

Results: Besides the patients with primary tumors characterized as pT4b (63%), the patients with pT4a tumors and pT3 tumors close to 4 mm in tumor thickness also received initial whole-body imaging. In 42.6% of the patients undergoing ¹⁸F-FDG-PET/CT, the imaging results led to a change in the diagnostic or therapeutic procedure following on from this. In 29% of cases, sentinel lymph node biopsy was no longer necessary. The sensitivity and specificity of ¹⁸F-FDG-PET/CT were 66.0% and 93.0%, respectively.

Conclusion: Whole-body imaging as a primary diagnostic tool is highly valuable and influences the subsequent diagnostic and therapeutic procedures in a considerable number of patients with a relatively high tumor thickness. It can help avoid the costs and invasiveness of redundant SLNB and simultaneously hasten the staging of patients at the time of diagnosis.

Keywords: PET-CT; diagnosis; imaging; melanoma; staging.

Figure 1

Indication for whole-body imaging as the primary staging procedure in melanoma patients. High tumor thickness of the primary tumor and clinical or sonographic suspicion of metastasis or acrolentiginous melanoma of unknown or undeterminable tumor thickness (ALM) were indications for primary whole-body imaging in melanoma patients (A). Tumor thickness of primary pT3 and pT4 tumors (mean ± sd) in (B) and ulceration of the primary tumor (C) are relevant indicators for primary whole-body staging. The final staging results of all patients under investigation are shown in (D).

Figure 2

Results of ¹⁸F-FDG-PET/CT imaging and implications for the subsequent diagnostic procedure. (A) shows the ¹⁸F-FDG-PET/CT results categorized as no metastatic finding or different metastatic manifestations. The proportion of altered procedures after ¹⁸F-FDG-PET/CT imaging (B) is divided into altered surgical procedure, neoadjuvant therapy, and declined surgical procedure and further diagnostics because of the suspicion of a secondary malignancy (C). (D) depicts the rate of indication for sentinel lymph node biopsy. (E) summarizes the ¹⁸F-FDG-PET/CT results and their final interpretation. One patient had an unclear pulmonary nodule, compatible with metastasis, but histologically identified as carcinoid and no indication of lymph node metastasis, but micrometastasis in SLNB (indicated by *). The patient was excluded for the calculation of the positive and negative predictive value.

Figure 3

Images from ¹⁸F-FDG-PET/CT at melanoma diagnosis. Fused ¹⁸F-FDG-PET/CT (left), CT (middle) and ¹⁸F-FDG-PET (right) scans. Metastases are indicated by red arrows. (A) shows an axillary lymphatic metastasis in a 55-year-old patient and (B) depicts a metastasis in the autochthonous back muscles in a 66-year-old patient.

Figure 4

S100 and LDH serum concentrations and PET/CT results. S100 (A) and LDH (B) serum levels in ng/L are depicted for patients with melanoma-associated positive and negative PET/CT results (p > 0.05). Values above the reference levels (S100: 100 ng/L; LDH: 244 ng/L) are shown in red.