Mohs micrographic surgery for basal cell carcinomas: results of a Spanish retrospective study and Kaplan–Meier survival analysis of tumour recurrence

BACKGROUND: Mohs micrographic surgery (MMS) is a specialized procedure usually limited to specific indications (e.g. high-risk basal cell carcinomas [BCCs]). OBJECTIVE: To determine the recurrence rate of MMS for BCC at a tertiary referral centre in Barcelona, Spain. METHODS: Review of medical records of patients undergoing 534 consecutive MMS interventions for confirmed BCCs. The main outcome measure was biopsy-proven recurrence of BCC at the same anatomical location after MMS. RESULTS: A total of 489 patients underwent MMS for 534 BCCs from April 1999 to December 2011. The patients’ mean age was 66 years. The most frequent location was the nasal/perinasal region (38.4%, n = 205). The surgical interventions of 47.9% (n = 256) were for primary BCCs and 52.1% (n = 278) procedures were for recurrent or residual BCCs. The mean follow-up was 30.5 months (range 1–145 months). Thirty-two recurrences were identified in total. The raw recurrence rate following MMS for primary BCCs was 1.2% (3/256) compared to 10.4% (32/278) for recurrent BCC. On multivariate analysis (Cox proportional hazard model) only prior treatment (P = 0.018, hazard ratio [HR] 4.68 with 95% confidence intervals [CI] 1.30–16.79), multiple prior treatments (P = 0.013, HR 2.72 [95%CI 1.24–5.96]), and healing by secondary intention (P = 0.041, HR 2.88 [95%CI 1.04–7.97]) were independent prognostic factors of recurrence after MMS. LIMITATIONS: The limitations of our study are those of a retrospective study. CONCLUSION: Mohs micrographic surgery for primary high-risk BCCs has a high success rate but the cumulative probability of recurrence increases significantly when tumours with recurrences are referred for MMS.