Combination topical 5-fluorouracil 5%/calcipotriene 0.005% cream for the treatment of cutaneous in situ squamous cell carcinoma: a pilot study of efficacy and risks

Background:
Various treatment options, including surgical excision and non-invasive modalities, exist for managing squamous cell carcinoma in situ (SCCIS). This pilot study investigated the safety and efficacy of a compounded 5-FU 5%/calcipotriene 0.005% cream in the treatment of SCCIS in this single-center, single-blinded, randomized study.
Methods:
Patients were randomized into one of three groups: a placebo group, a 7-day application group, or a 14-day application group. All patients received surgical excision at least 20 days after completion of cream application.
Results:
Significant differences in histological clearance of SCCIS between the treatment and control groups were identified (p<0.001). There was a complete histological clearance in 83.3% and 87.5% of patients in the 7- and 14-day treatment groups, respectively. All patients in the placebo group showed residual tumor on histological evaluation. Adverse effects, including redness, itching, and burning, were more commonly reported in the 14-day treatment group. Two patients in the treatment groups developed reactive squamous proliferations within the scar approximately 61-96 days after excision.
Conclusion:
Topical 5-fluorouracil 5%/calcipotriene 0.005% cream is effective in inducing histological clearance of SCCIS when applied twice daily for 7 or 14 days. Reactive squamous atypia may occur in surgical scars if excision is performed within 35 days of cream application.