Adjuvant topical fluorouracil therapy for persistent superficial basal cell carcinoma post-Mohs micrographic surgery: long-term follow-up

Background In cases where invasive basal cell carcinoma (BCC) subtypes (e.g., infiltrative and nodular) are treated with Mohs micrographic surgery (MMS), some patients may have residual superficial BCC (sBCC) following several stages of MMS after the invasive component has been cleared. Topical 5-fluorouracil (5-FU) is a well-studied chemotherapeutic agent, but long-term postoperative adjuvant outcome data are limited.Methods We conducted a retrospective chart review from January 1, 2014, to April 14, 2025, including patients with residual sBCC who elected to forgo further Mohs stages and switch to 6 to 8 weeks of 5-FU following the final Mohs stage. A total of 139 patients were included, with a mean age of 78.5 years. Out of 166 BCC cases, 154 initial tumors had an invasive component (infiltrative and nodular subtypes).Results We report a recurrence rate of 3.61% (6 of 166 cases) over a median follow-up period of 41.9 months.Conclusion Our study demonstrates the potential effectiveness of topical 5-FU as an alternative adjuvant therapy for clearance of residual sBCC in patients with surgical fatigue.