Surgical Approach to Primary Cutaneous Melanoma

Is a Wider Margin (2 cm vs. 1 cm) for a 1.01-2.0 mm Melanoma Necessary?

BACKGROUND

The current NCCN recommendation for resection margins in patients with melanomas between 1.01 and 2 mm deep is a 1-2 cm radial margin. We sought to determine whether margin width had an impact on local recurrence (LR), disease-specific survival (DSS), and type of wound closure.

METHODS

Melanomas measuring 1.01-2.0 mm were evaluated at a single institution between 2008 and 2013. All patients had a 1 or 2 cm margin.

RESULTS

We identified 965 patients who had a 1 cm (n = 302, 31.3 %) or 2 cm margin (n = 663, 68.7 %). Median age was 64 years, and 592 (61.3 %) were male; 32.5 and 48.7 % of head and neck and extremity patients had a 1 cm margin versus 18.9 % of trunk patients (p < 0.001). LR was 2.0 and  2.1 % for a 1 and 2 cm margin, respectively (p = not significant). Five-year DSS was 87 % for a 1 cm margin and 85 % for a 2 cm margin (p = not significant). Breslow thickness, melanoma on the head and neck, lymphovascular invasion, and sentinel lymph node biopsy (SLNB) status significantly predicted LR on univariate analysis; however, only location and SLNB status were associated with LR on multivariate analysis. Margin width was not significant for LR or DSS. Wider margins were associated with more frequent graft or flap use only on the head and neck (p = 0.025).

CONCLUSIONS

Our data show that selectively using a narrower margin of 1 cm did not increase the risk of LR or decrease DSS. Avoiding a 2 cm margin may decrease the need for graft/flap use on the head and neck.

In vivo and in silico pharmacokinetics and biodistribution of a melanocortin receptor 1 targeted agent in preclinical models of melanoma

The melanocortin 1 receptor (MC1R) is overexpressed in most melanoma metastases, making it a promising target for imaging of melanomas. In this study, the expression of MC1R in a large fraction of patients with melanoma was confirmed using mRNA and tissue microarray. Here, we have characterized the in vivo tumor and tissue distribution and pharmacokinetics (PK) of uptake and clearance of a MC1R specific peptidomimetic ligand conjugated to a near-infrared fluorescent dye. We propose an interdisciplinary framework to bridge the different time and space scales of ligand-tumor-host interactions: intravital fluorescence microscopy to quantify probe internalization at the cellular level, a xenograft tumor model for whole body pharmacokinetics, and a computational pharmacokinetic model for integration and interpretation of experimental data. Administration of the probe into mice bearing tumors with high and low MC1R expression demonstrated normalized image intensities that correlated with expression levels (p < 0.05). The biodistribution study showed high kidney uptake as early as 30 min postinjection. The PK computational model predicted the presence of receptors in the kidneys with a lower affinity, but at higher numbers than in the tumors. As the mouse kidney is known to express the MC5R, this hypothesis was confirmed by both coinjection of a ligand with higher MC5R affinity compared to MC1R and by injection of lower probe concentrations (e.g., 1 nmol/kg), both leading to decreased kidney accumulation of the MC1R ligand. In addition, through this interdisciplinary approach we could predict the rates of ligand accumulation and clearance into and from organs and tumors, and the amount of injected ligand required to have maximum specific retention in tumors. These predictions have potential to aid in the translation of a targeted agent from lab to the clinic. In conclusion, the characterized MC1R-specific probe has excellent potential for in vivo detection of melanoma metastases. The process of cell-surface marker validation, targeted imaging probe development, and in vitro, in vivo, and in silico characterization described in this study can be generally applied to preclinical development of targeted agents.

Synthesis and characterization of a melanoma-targeted fluorescence imaging probe by conjugation of a melanocortin 1 receptor (MC1R) specific ligand

The incidence of malignant melanoma is rising more rapidly than that of any other cancer in the United States. The melanocortin 1 receptor (MC1R) is overexpressed in most human melanoma metastases, thus making it a promising target for imaging and therapy of melanomas. We have previously reported the development of a peptidomimetic ligand with high specificity and affinity for MC1R. Here, we have conjugated near-infrared fluorescent dyes to the C-terminus of this ligand via lysine-mercaptopropionic acid linkers to generate MC1R specific optical probes (MC1RL-800, 0.4 nM K(i); and MC1RL-Cy5, 0.3 nM K(i)). Internalization of the imaging probe was studied in vitro by fluorescence microscopy using engineered A375/MC1R cells and B16F10 cells with endogenous MC1R expression. The in vivo tumor targeting of MC1RL-800 was evaluated by intravenous injection of probe into nude mice bearing bilateral subcutaneous A375 xenograft tumors with low MC1R expression and engineered A375/MC1R tumors with high receptor expression. Melanotic B16F10 xenografts were also studied. Fluorescence imaging showed that the agent has higher uptake values in tumors with high expression compared to low (p < 0.05), demonstrating the effect of expression levels on image contrast-to-noise. In addition, tumor uptake was significantly blocked by coinjection of excess NDP-α-MSH peptide (p < 0.05). In conclusion, the MC1R-specific imaging probe developed in this study displays excellent potential for the intraoperative detection of regional node involvement and for margin detection during melanoma metastasis resection.

1 or 2 cm margins of excision for T2 melanomas: do they impact recurrence or survival?

BACKGROUND

NCCN guidelines recommend 1 or 2 cm margins for melanomas 1-2 mm (T2 melanomas) in depth; however, no head-to-head comparison has been performed. We hypothesized 1- or 2-cm margins would have similar local recurrence (LR) and overall survival (OS).

METHODS

An institutional database was queried for patients with 1.0-2.0 mm melanomas treated from July 1995 to January 2011. All had wide excision and sentinel lymph node biopsy. Patients without documented surgical margins or follow-up were excluded. Clinicopathologic and recurrence data were reviewed. Univariate and multivariate analyses were performed.

RESULTS

Of 2,118 patients, 1,225 met study criteria. Of these, 576 had complete data: 224 (38.9%) had 1 cm margins and 352 (61.1%), 2 cm margins. Median follow-up was 38 months. Mean age was 52.6 years (range 11.3-86.7). Mean thickness was 1.27 and 1.48 mm (1 and 2 cm, respectively, p<0.001) with ulceration more common in the 2 cm group (12.3 and 21.3%, respectively; p=0.009). LR was 3.6 and 0.9% in the 1 cm versus 2 cm group, respectively (p=0.044). OS was 29.1 months with 1 cm and 43.7 months in the 2 cm group. On multivariate analysis, only head and neck location and nodal status were associated with overall survival.

CONCLUSIONS

In this series, 1 cm margins were associated with a small increase in LR that did not impact OS. This is concordant with the NCCN recommendations; however, a prospective, randomized trial would be optimal.