Clinical relevance of 18F-FDG PET/CT lower-limb imaging in patients with malignant cutaneous melanoma.

Abstract

The aim of this study was to assess the clinical relevance of imaging the lower limbs when using 2-(F)-fluoro-2-deoxy-D-glucose (F-FDG) positron emission tomography with computed tomography (PET/CT) for malignant cutaneous melanoma in patients without previously known or suspected primary or metastatic melanoma lesions in the lower limbs. We retrospectively assessed 880 consecutive F-FDG PET/CT scans performed for adult patients in a context of suspected melanoma spanning a period of 5 years. All scans were correlated with the associated patient records (clinical history, physical examinations, and pathology reports), as well as follow-up imaging examinations, up until at least 6 months after the end of the study. Among the 461 whole-body scans included for analysis, 109 reported unusual activity in the lower limbs, but with at most 21 scans showing lower-limb lesions attributed to melanoma on follow-up. No scan showed melanoma lesions exclusively in the lower limbs, and in no case did imaging the lower limbs upstage a patient. Imaging the lower limbs changed the actual clinical management of the melanoma for only one patient, with precautionary local radiation therapy administered following the detection of an asymptomatic distal femur bone metastasis in an otherwise plurimetastatic patient headed for palliative care. Our study, the largest of its kind, confirms that, when using F-FDG PET/CT for staging, restaging, or surveillance of malignant cutaneous melanoma in patients without previously known or suspected lower-limb melanoma lesions, imaging the lower extremities offers little additional clinically relevant information and stopping the scan at the proximal thighs has essentially no clinical impact.