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Melanoma pigmentation affects melanoma-specific survival and provides a potential target for radiopharmaceutical-based imaging and therapy.

8563 Background: The significance of melanoma pigmentation is poorly studied despite being fundamental to melanocyte biology. We examined its pathological and clinical associations in primary melanoma; and as a diagnostic target for the novel melanin binding PET tracer [18F]MEL050 in advanced melanoma.


METHODS
Data collected prospectively from 253 patients with primary cutaneous melanoma. Standard histological features, BRAF (exon 15) and NRAS (exon 2) mutation status, and clinical outcome results were correlated against pigmentation assessed macroscopically by a pathologist. Second, in 5 patients with stage III/IV melanoma planned for resection, we performed a pilot study of [18F]MEL050-PET in patients with positive FDG-PET imaging.


RESULTS
Pathological and outcome data obtained for 253 and 216 patients respectively with a median follow-up of 47 months. Lack of melanin was present in 46 of 253 (18.2%) of tumors and was associated with increased thickness, nonsuperficial spreading histotype, presence of ulceration and BRAF WT. On Cox proportional hazards analysis, amelanosis was an independent predictor of worse melanoma specific survival (MSS) and relapse free survival (RFS) but not overall survival (OS) (Table). [18F]MEL050 uptake was demonstrated in 3 of 3 patients with melanotic tumors with 60 min standardized uptake values (SUV) of 7, 10.4, 10.6. No significant tumor [18F]MEL050 signal in 2 of 2 patients with amelanotic tumors, or in 1 FDG-positive mediastinal node, presumed inflammatory.


CONCLUSIONS
Loss of melanin synthesis occurs occasionally in primary melanomas and more frequently in metastases, and in our patient cohort was associated with a more aggressive phenotype and worse outcomes. [18F]MEL050 may thus allow noninvasive characterization of this apparently important prognostic factor. [Table: see text].