Topographical and Chronological Analysis of Thin Cutaneous Melanoma's Progressions: A Multicentric Study

Abstract

A great portion of cutaneous melanoma's diagnoses nowadays is attributed to thin tumors with up to 1 mm in Breslow thickness (hereafter thin CMs), which occasionally metastasize. The objective of this study was to identify thin CM's metastatic patterns from a topographical and chronological standpoint. A total of 204 cases of metastatic thin CMs from five specialized centers were included in the study, and corresponding data were collected (clinical, epidemiological, histopathological information of primary tumor and the number, anatomical site, and time intervals of their progressions). First progressions occurred locally, in regional lymph nodes, and in a distant site in 24%, 15% and 61% of cases, respectively, with a median time to first progression of 3.10 years (IQR: 1.09-5.24). The median elapsed time between the first and second progression and between the second and third progression was 0.82 (IQR: 0.34-1.97) and 0.49 (IQR: 0.21-2.30) years, respectively, while the median survival time was about 4 years since first progression. Furthermore, the sequences of locations and time intervals of the progressions were associated with the clinicopathological and demographic features of the primary tumors along with the features of the preceding progressions. In conclusion, the findings of this study describe the natural history of thin CMs, thus highlighting the necessity to identify subgroups of thin CMs at a higher risk for metastasis and contributing to the optimization of the management and follow-up of thin CM patients.

Keywords: cutaneous melanoma; invasive melanoma; melanoma progressions; metastatic melanoma; metastatic pattern; progression pattern; thin melanoma; thin melanoma metastasis; thin melanoma natural history; thin melanoma progression.

Figure 1

Flowchart of the patients’ selection.

Figure 2

Progression pathways. (A) Panel A includes Bologna center and, hence, data on first and second progressions. Panel B excludes Bologna center cases. (B) Schematic presentation of the topographical sequences of progressions for the entire sample.

Figure 3

Nonparametric cumulative incidence of second progression with respect to time since first progression.

Figure 4

Nonparametric cumulative incidence of the type of second progression with respect to time since first progression. Solid line represents the subgroup of local progressions of thin CMs, dashed line represents the subgroup of nodal ones, and dash–dotted line represents the subgroup of distant ones.

Figure 5

Nonparametric cumulative incidence of third progression with respect to time since second progression.

Figure 6

Nonparametric cumulative incidence of the type of third progression over time since second progression. Solid line represents the subgroup of local progressions of thin CMs, dashed line represents the subgroup of nodal ones, and dash–dotted line represents the subgroup of distant ones.

Figure 7

Nonparametric cumulative incidence of melanoma-specific mortality with respect to time since first progression.