Risk Factors for Complicated Mohs Surgery in the South Sweden Mohs Cohort.

BACKGROUND: Mohs micrographic surgery (MMS) is a precise, tissue-sparing surgical technique that offers superior cure rates compared to traditional surgical excision. However, the degree of difficulty of MMS depends on many variables and, consequently, the number of surgical stages required for each case is quite unpredictable.

OBJECTIVES: To identify risk factors for complicated MMS, defined as MMS requiring ≥3 stages.

METHODS: In a cohort study design, data was prospectively collected from 612 patients that underwent MMS for basal cell carcinoma (BCC) at the Department of Dermatology, Skåne University Hospital, Lund, between 2009 and 2020. Univariate and multivariate logistic regression were used to estimate risk of MMS requiring ≥3 stages. Due to risk of multicollinearity between recurrent or incompletely excised BCC and previous treatments, a partially and a fully adjusted multivariate logistic regression model were constructed.

RESULTS: In fully adjusted multivariate analyses, age (odds ratio (OR) 1.02; confidence interval (CI) 95% 1.00-1.04), previous cryotherapy (OR 2.3; CI 95% 1.1-4.8) and >1 previous surgery (OR 3.4; CI 95% 1.5-7.7) were significantly associated with risk of complicated MMS. Recurrent BCC was associated with risk of complicated MMS in partially adjusted multivariate analyses, but not in the fully adjusted analyses. In this highly selected cohort, histopathological subtype and tumour localisation were not associated with risk of complicated MMS.

CONCLUSIONS: Older age and tumours previously treated with cryotherapy or multiple prior surgeries increased risk of MMS requiring ≥3 stages. Whether recurrent BCC is an independent risk factor for complicated MMS needs further evaluation. Knowledge of these risk factors may ameliorate planning of Mohs surgeries.