Waiting time for Mohs Micrographic Surgery and the associated increase in lesion size of basal cell carcinoma

The first-line treatment for basal cell carcinoma (BCC) involved either surgical excision (SE) or Mohs micrographic surgery (MMS). The current waiting time for MMS and whether this is associated with worsening of outcome is unknown. We aim to look at the waiting time for MMS upon review at the Outpatient Specialist Dermatology Clinic and the increase in lesion size during this time period.

A retrospective analysis of all patients who underwent MMS for biopsy-proven BCC over a duration of 5 years was performed. Variables analysed included patient age, sex, location, histologic subtype, lesion size at initial presentation, lesion size during MMS, defect size following MMS, waiting time for MMS, and projected defect size if lesions were treated with SE at earlier time point.

A total of 233 patients were included in the final analysis. The mean wait time between referral to MMS was 215.8±125.7 days. The mean maximum diameter of lesions was 9.34±5.23 mm at referral for MMS and 11.91±6.60 mm at presentation for MMS, hence an increase of 3.01±3.03 mm (p=0.001, paired t-test), which equates to 1.41±0.42 times increase. The mean maximum diameter of the actual defect size post-MMS was 18.03±9.45mm, while the projected diameter of defect post SE was 15.29±5.71 mm, hence, smaller by 3.27±5.51 mm (p=0.001, paired t-test) compared with actual defect size post-MMS.

This study highlights that the lesion grows significantly during the long wait for MMS. Hence, an increase in capacity for MMS is essential to reduce the waiting time for surgery which could lead to a defect which is easier to reconstruct with better outcome for patients.