Factors Linked to the Metastatic Spread of Malignant Cutaneous Melanoma to the Lower Extremities in a Retrospective 18F-FDG PET/CT Cohort

Abstract

BackgroundThe goal of the present study was to assess the factors linked to the spread of malignant cutaneous melanoma to the lower limbs in patients without previously known or suspected primary or metastatic melanoma lesions in the lower extremities. Patients and MethodsWe retrospectively reviewed 461 consecutive whole-body 2-(18F)fluoro-2-deoxy-d-glucose (18F-FDG) positron emission tomography with computed tomography (PET/CT) scans performed during a 5-year period for adult patients with histopathologically proven cutaneous primary melanoma but without previously known or suspected lower limb melanoma lesions. All PET/CT scans were correlated with the patient records covering a period of ≥ 6 months after study end, including detailed pathology reports and follow-up imaging results. ResultsOnly 21 PET/CT scans (4.6%; 95% confidence interval, 3.00%-6.86%) showed lower limb lesions attributable to melanoma during the follow-up period, with most scans showing extensive metastases elsewhere. However, no scan revealed melanoma lesions solely in the lower extremities (0%; 95% confidence interval, 0%-0.83%). The time that had elapsed since primary lesion resection was significantly linked statistically to the spread of melanoma to the lower extremities (P = .03). The presence of metastatic regional lymph nodes during initial staging was also significantly linked statistically to lower limb melanoma lesions later in the disease course (P = .006). ConclusionFor adults with cutaneous melanoma but without previously known or suspected melanoma lesions in the lower extremities, metastatic spread to the lower limbs is infrequent. Thus, imaging can be stopped at the proximal thighs without affecting clinical management. More clinical attention should be devoted to the lower extremities as time passes and if metastases have been documented elsewhere.