Response to "Mohs surgery for early-stage Merkel cell carcinoma (MCC) achieves local control better than wide local excision +/− radiation therapy with no increase in MCC-specific death"

Dear Editor,

We reviewed Terushkin et al.’s recent article in the International Journal of Dermatology with great interest.¹ The authors retrospectively evaluated 53 patients with Merkel cell carcinoma (MCC) treated with Mohs micrographic surgery (MMS) monotherapy. Their analysis demonstrated 5-year MCC-specific survival rates of 91.2% and 68.6% for Stage I and Stage IIA disease, respectively, and a recurrence rate of 33.9% encompassing local, in-transit/satellite, nodal, and distant recurrences over a median follow-up of 2.7-years. Compared to historical controls, the authors concluded that MMS monotherapy has comparable efficacy to the standard of care, which is wide local excision (WLE) with sentinel lymph node biopsy (SNLB) +/− adjuvant radiation therapy (RT) for localized disease as recommended by NCCN guidelines.²

While patients in Terushkin et al.’s investigation did not have clinically palpable lymphadenopathy, there are no data on sentinel node status for pathologic staging, which is central to management of MCC given the high prevalence (approximately 33% across numerous studies) of occult nodal metastasis in patients with clinical N0 disease.³ Given the lack of baseline pathologic nodal evaluation, it is unclear how the authors accurately determined nodal recurrence.

The authors do not address whether there was a selection process or algorithm for choosing MMS over WLE in their clinic during this 18-year time period, introducing a possible source of bias. Evaluating the efficacy of MMS vs. WLE + RT is difficult without prospective data, and retrospective studies have to control for potential confounders and selection bias, which may have influenced the outcomes of the present study, especially in the absence of head-to-head comparisons. In one study in the National Cancer Database, an analysis of 6227 patients demonstrated that WLE with RT had improved overall survival over MMS alone after accounting for age, sex, comorbidities, primary site of lesion, and tumor size on propensity score matched analysis.⁴

While the authors suggest that MMS may obviate the need for adjuvant radiation, a locoregional recurrence rate of 35.7% (20/56 primaries) was observed in their study, which could plausibly have been lower if occult nodal disease were detected and radiation was given. Although MMS has demonstrated low recurrence rates in other cutaneous neoplasms, in some investigations, this approach has resulted in local recurrence rates exceeding 20% when applied for MCC.⁵ Furthermore, a growing body of evidence suggests that surgical margins of at least 1 cm plus adjuvant RT compared to surgery alone are associated with improved overall survival and reduced risk of locoregional recurrence for patients with Stage I and II disease.^{6, 7}

The study by Terushkin et al. offers a unique perspective on MMS for early stage MCC; however, given the aggressive nature of MCC with high rates of recurrence and clinically occult nodal spread, these results are unlikely to influence current guidelines which recommend SLNB and surgical excision with wide margins (>1 cm) with the addition of adjuvant radiation when larger margins are not clinically feasible.