A review of Mohs micrographic surgery for skin cancer. Part 3: Squamous cell carcinoma

This review presents and discusses the evidence for MMS to treat cutaneous squamous cell carcinoma (cSCC). The MEDLINE, Embase and Cochrane databases were searched; 39 papers were identified for recurrence and 2 papers for cost-effectiveness. We included all clinical trials and observational studies, including retrospective reports, and excluded editorials and systematic reviews or meta-analyses. We categorized the evidence under the following headings: tumour recurrence, specific site outcomes (ear, lip, scalp and periocular), cSCC with perineural invasion, and cost-effectiveness. Although there are many observational studies indicating the potential benefits of MMS in the management of certain cSCCs, no randomized controlled trials (RCT) were identified. The evidence from comparitor studies suggests that MMS has a lower recurrence rate than that of other treatments for cSCC, including standard excision. Many studies identified were single-armed, but did demonstrate a low to very low recurrence rate of cSCC following MMS. A single recent study suggests MMS for intermediate cSCC is highly cost-effective compared with wide local excision when all-in costs are considered. Since the overall quality of included studies was mixed and highly heterogeneous, further methodologically robust studies with comparator arms or comprehensive long-term registry data would be valuable. It would be ideal to employ a definitive multicentre RCT but given the evidence to date and multiple advantages to MMS, the lack of clinical equipoise makes this difficult to justify. Comparison with current modalities would likely not be ethical/achievable on a like-for-like basis given MMS provides 100% margin assessment, enables histological clearance prior to reconstruction, and minimizes the removal of uninvolved tissue.