. This approach has the potential to reduce morbidity and cost associated with treatment “without compromising patient outcomes in a selected population of lesions,” the authors say.
“Currently, there is uncertainty regarding the optimal excision margin for MIS, with different guidelines recommending a range between 5 and 10 mm,” corresponding author Cong Sun, MD, of Mater Hospital Brisbane Raymond Terrace, South Brisbane, Queensland, Australia, and colleagues wrote in the study, which was published in JAMA Dermatology. “In addition, studies using the Mohs micrographic surgery technique have suggested that wider margins, up to 18 mm, may be required for MIS in some settings.”
To further examine the use of 5-mm margins for excision of small MIS on low-risk sites, the researchers retrospectively evaluated 351 MIS lesions diagnosed in 292 patients between January 1, 2011, and November 30, 2018. Lesions were eligible for analysis if a 5-mm excisional margin was documented on the operation report and if there was more than 5 years of site-specific follow-up after wide local excision. Lesions with undocumented margins were excluded from analysis, as were those with fewer than 5 years of follow-up, and those that required more than one wide local excision.
The mean age of patients was 60.3 years, 55.5% were female, and the mean dimensions of the lesions was 6 × 5 mm. The most common subtype of melanoma diagnosed was superficial spreading melanoma (50.4% of lesions), followed by lentigo maligna (30.5%) and lentiginous MIS (19.1%). Nearly half of the lesions were on the trunk (47.9%), followed by the upper limb (27.4%), lower limb (16.8%), neck (4%), face (3.4%), and scalp (0.6%). As for the size of lesions, 78.1% were < 10 mm long and 88.9% were < 10 mm wide.
Nearly 71% (248) of the lesions were treated with an initial excisional biopsy, and 29.3% (103) underwent an initial shave excision. Median follow-up was 7 years.
Only three of the 351 lesions (0.9%) had a local recurrence, with no regional recurrence or metastatic spread, and 99.1% had no recurrence. The recurrences were reexcised “with clear margins” and after at least 5 years of follow-up, no further recurrences were reported, the authors said.
In Mohs surgery studies, reported recurrence rates for MIS have been “between 0.26% and 1.1%, with excisional margins between 6 and 12 mm required,” the authors noted. “This study demonstrated a comparable 0.9% recurrence rate achieved with a conservative 5-mm excisional margin. This shows that using a 5-mm margin for MIS of smaller size (< 10 mm) may reduce morbidity and cost associated with treatment without compromising patient outcomes in a selected population of lesions.”
The researchers recommended additional studies to confirm their findings and acknowledged certain limitations of their analysis, including its retrospective, single-center design and the predominantly small sizes of the lesions.
In an accompanying editorial, John A. Zitelli, MD, of the University of Pittsburgh, Pittsburgh, Pennsylvania, said that the margin measurement used by the researchers was another limitation. “Before the excision with a 5-mm margin was performed, the diagnosis of MIS was obtained by shave biopsy or excisional biopsy with a 2- to 3-mm margin of clinically normal skin,” Dr. Zitelli wrote. “Therefore, in patients without a 2- to 3-mm biopsy margin, a minimum surgical margin of 7-8 mm would be required to achieve a similar true negative excision margin.”
Also, he continued, the exclusion of lesions with wide subclinical extension that required wider margins “weakens the conclusion that 5 mm would be an effective treatment for all MIS.”
Hugh Greenway, MD, head of Mohs micrographic surgery and director of cutaneous oncology at Scripps Cancer Center, San Diego, who was asked to comment on the study, said that clinicians continue to search for the optimum smaller surgical margin for MIS. “This can be challenging with the variability of MIS based on location and other factors,” Dr. Greenway told this news organization. “This Australian retrospective study notes that for selected, well-defined 6 × 5 mm lesions of low-risk body sites (mainly torso and limbs), a 5-mm surgical margin can provide a high cure rate. The authors note further studies are indicated. Thus, for selected lesions in selected locations, the 5-mm surgical margin may be appropriate for MIS.”
The study authors, Dr. Zitelli, and Dr. Greenway reported no financial disclosures.
A version of this article appeared on Medscape.com.