Topical 30% Ascorbic Acid in DMSO for Treatment of Cutaneous Squamous Cell Carcinoma In Situ.

BackgroundCutaneous squamous cell carcinoma in situ (SCCIS) is a common nonmelanoma skin cancer with rising incidence and substantial treatment costs. While Mohs micrographic surgery remains the standard of care, cost, accessibility, and cosmetic concerns limit its use for some patients. Topical alternatives such as imiquimod and 5-fluorouracil are associated with variable efficacy and frequent adverse effects. ObjectiveTo evaluate the efficacy and tolerability of a 30% ascorbic acid (vitamin C) solution in 95% dimethyl sulfoxide (DMSO) for the treatment of biopsy-confirmed SCCIS. MethodsIn this open-label study, 17 patients with 27 histologically confirmed SCCIS lesions applied 30% ascorbic acid in DMSO topically twice daily for 12 weeks. Lesion size and histologic resolution were assessed by repeat biopsy at week 12. Primary outcome was complete resolution of SCCIS; secondary outcomes included lesion size reduction and adverse events. ResultsComplete histologic resolution occurred in 15 of 27 lesions (56%), while 44% of lesions showed >85% reduction in size. The mean reduction in lesion area was 71%. Only 2 lesions (7%) failed to respond. Most residual lesions demonstrated actinic atypia without carcinoma and were successfully treated with cryotherapy. No patients discontinued due to adverse effects. Ninety-four percent of participants (16/17) avoided surgical excision. ConclusionsTopical 30% ascorbic acid in DMSO demonstrated promising efficacy and excellent tolerability in the treatment of SCCIS, offering a potential noninvasive alternative to surgery. Larger, controlled trials are warranted.