The Value of Technetium-99m Labeled Alpha-Melanocyte- Stimulating Hormone (99mTc-α-MSH) in Diagnosis of Primary and Metastatic Lesions of Malignant Melanoma

Objective(s): Malignant melanoma is the most lethal type of skin cancers with unfavorable prognosis. Alpha-MSH peptide analogues have a high affinity for melanocortine-1 (MC1) receptors on melanocytes overexpressing in malignant melanoma cells. Pre-clinical studies have shown promising results for radiolabeled MSH imaging in this malignancy. The purpose of this study is to assess the diagnostic value of 99mTc-α-MSHimaging in malignant melanoma.Methods: Twenty-one patients (13 men) with pathologically confirmed malignant melanoma with or without metastatic distribution were included in this study. 740-1110 MBq 99mTc-α-MSH was injected and whole body scans were performed 20, 120 and 240 minutes post injection and were assessed both qualitatively and semi-quantitatively using target (T) to background (BG) ratio.Results: The T/BG ratio for the primary tumor bed was 2.51±2.26, 2.56±2.48 and 1.92±1.79 minutes in the whole body scans 20, 120 and 240 minutes post injection, respectively. The sensitivity, specificity, negativeand positive predictive values were 75%, 80%, 50% and 92% for primary lesion and 25%, 100%, 68% and 100% for distant metastasis, respectively.Conclusion: 99mTc-α-MSH is a newly introduced agent for diagnosis of tumoral lesions in malignant melanoma. Our study showed a high sensitivity with this modality in primary lesions as well as lymph nodeinvolvements. However the detection rate was not high in distant metastasis. The preliminary results are promising especially as a new complementary imaging method in management of malignant melanoma.