Margin Size Associated With Risk of Local Recurrence From Melanoma In Situ

Pathological excision margins of 4 mm or more may be a reliable indicator of the risk of recurrence of melanoma in situ (MIS) following surgical excision of the cancer, according to findings from a new study that investigated the ability to predict local disease recurrence.

“Reliable evidence to guide the management of MIS and minimize the risk of recurrence is lacking,” the authors wrote. “The purpose of this study was to identify clinicopathological predictors of local recurrence in a large cohort of patients with MIS and assess the effect of excision margins on long-term outcomes for patients with MIS.” They recently published the results of their retrospective case-control study in Journal of the American Academy of Dermatology International.

Outcomes were investigated among 1407 patients who received an MIS diagnosis between January 2008 and December 2012 at the Melanoma Institute of Australia. Their complete clinical, pathologic, and follow-up data were supplied by the treatment center’s research database. Because Australian Melanoma Management Guidelines recommend excision margins of at least 5 mm, the investigators identified a subset of patients whose margins were less than 4 mm.

From among the overall study population, the 2.5% (n = 34) of patients who developed local recurrence became the study group, with the remaining 97.5% (n = 1373) forming the control group. Before and after matching, most participants in both groups were male (52.9% in both instances for the study group and 54.6% and 55.9%, respectively, for the control group), and with the exception of the control group before matching, in which 50.6% were younger than 60 years, most patients were older than 60 years before and after matching (58.8% in both instances for the study group and 61.8% after matching for the control group).

The head and neck region was the most common site of MIS recurrence (61.8%), followed by lower and upper limbs (14.7% each) and the trunk (8.8%). In addition, pathological margins of less than 4 mm were close to 2.5 times more common among the study group than the control group: 67.6% vs 27.7%. However, 53% of those in the study group underwent subsequent wider excision following their initial biopsy. The median time to local recurrence was 20 months.

Between the study and control cohorts, median follow-up times varied widely. The overall follow-up was 5.7 (95% CI, 5.2-6.2) years, but this was much shorter in the study cases vs the control cases: 4.4 (95% CI, 0.4-9.7) vs 6.2 (2.0-10.3) years. Each of the 4 patients who had local recurrence that subsequently led to metastatic disease died, “with no other primary melanoma to explain the distant metastasis,” the authors noted.

Following matching, pathological margins of less than 4 mm were again much more common among the patients with local recurrence vs those who did not have local recurrence: 67.6% vs 44.1%. After this finding, the authors again divided their study population, but this time by excision margin: less than 4 mm (group 1) vs 4 or more mm (group 2).

Following this subanalysis, excision margins of less than 4 mm were more often associated with older age, head and neck location, higher all-cause mortality, and local recurrence. Further, close to twice as many patients in group 1 developed local recurrence compared with group 2, 67.6% vs 32.4%, and any-cause mortality was more common in group 1 vs group 2, at 9.5% vs 4.7%.

“It is important to note that most guidelines recommend surgical margins but do not specify desirable pathological margins for the management of MIS,” the authors concluded. “Our results suggest that clinicians should discuss with their patients the risks and benefits of more extensive surgery and should consider achieving pathological clearance margins of ≥4 mm whenever possible.”

Reference

Gaetano L, Domenico B, Lo SN, et al. Association between excision margins and local recurrence in 1407 patients with primary in situ melanomas. JAAD Int. 2022;8:102-108. doi:10.1016/j.jdin.2022.06.001