18F-FDG PET/CT in the evaluation of recurrent malignant melanoma

Objectives Objectives: Malignant melanoma causes significant morbidity and mortality with a high rate of recurrence risk as tumour thickness increases. The role of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in the surveillance of these tumours is not clear. The objective of this study was to evaluate the pattern of disease recurrence in patients with malignant melanoma who had had surgical resection of all malignant lesions.

Methods : A total of 112 patients (female n=65, male n=47) with malignant melanoma, median age 55 years (range 9 to 82 years), race: Caucasians (n=93), Blacks (n=19) were included. All patients had an initial 18F-FDG PET/CT scan done post-surgical excision of primary site and lymphadenectomy which was negative for residual malignant disease. The presence or absence of recurrence was based on histology and/or standardized clinical follow-up and 18F-FDG PET/CT.

Results : Among 25 patients who had confirmed recurrence of melanoma, PET/CT demonstrated solitary recurrence site seen in 40% of patients with recurrence (n=10) while the rest (n=15) showed two or more sites of disease recurrence. Lymph node metastases were the commonest site of disease recurrence seen in 20 patients (80% of all patients with recurrence). The other sites of recurrent disease were lungs (n=12), liver (n=5), skin (n=3), spleen (n=2), bone (n=2) and pancreas, brain, peritoneum, adrenal, breast, muscle (n=1 for each). The SUVmax ranged from 1.3 to 24.73. The Median time to recurrence was 23.5 months (range: 6 to 74 months). And of the 112 patients, the Lower limb was the commonest site of primary lesion (n=43). Others were trunk (n=33), head and neck including 3 patient with retinal melanoma (n=21), unknown site of primary (n=2), dual primary sites (n=2; one patient with lesion in lower limb and head & neck, the other with lesions in lower limb and trunk).

Conclusions 18F-FDG PET/CT may have greater value in patients with malignant melanoma as recurrence occurs within the first 2 years, and affects more than one site in the majority of patients. Lymph nodes are the most frequently involved site.