Decreasing loco-regional recurrence for oral cavity cancer with total Mohs margins technique

Mathieu Bergeron, Pierre Gauthier, Nathalie Audet

The conventional technique for cancer resection margin analysis studies only 0.1% of the surgical margins. Complete frozen section margins - also known as Mohs margins - allows for analysis of 100% of the surgical margins. The objective of our study is to compare oral cavity cancer loco-regional recurrence rates when treated by total frozen sections technique (Total Mohs margins) versus conventional margins. We conducted a multicenter retrospective cohort chart review. Loco-regional oral cancer recurrence rates were compared between patients treated with total Mohs margins (2007-2013) and patients treated with conventional margins techniques (2002-2007). After applying inclusion criteria, a total of 60 patients treated by total Mohs margins and 57 patients with conventional margins were identified. Patients had similar baseline cancer stages, pathological types, past head and neck cancers and comorbidities (all p > 0.05). One-year recurrence rate was lower (10.0% vs 21.1%, p = 0.019) in favor of Mohs total margins and stayed significantly lower at 5 years of follow-up. When adjusted for T grade with N0 disease, Mohs technique was still beneficial in loco-regional recurrence for Tis-T4N0 up to 2 years (10.5% vs 25.7%, z-score 1.849, p = 0.032). The Number Needed to Treat at 2 years of follow-up for this subgroup of patients (Tis-T4N0) is 6.6. Margins had to be retaken more often intra-operatively in Mohs technique (68.3% vs 12.3%, p < 0.0001), mainly for positive deep margins (48.6% of all margins, p = 0.028). Duration of surgery was not increased with Mohs vs conventional technique (380 min vs 475 min respectively, p = 0.025). Mohs total margins may result in a significant reduction in cancer recurrence rate at 5 years compare to conventional surgery. Moreover, duration of surgery was not increased when using Mohs technique when judiciously performed.