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The following is a summary of “5-fluorouracil 5% cream for squamous cell carcinoma in situ: Factors impacting treatment response,” published in the March 2025 issue of Journal of the American Academy of Dermatology by Lin et al. 

Researchers conducted a retrospective study to examine factors linked to complete clinical response (CCR) rates for squamous cell carcinoma (SCCis) in situ treated with 5-fluorouracil (5-FU) 5% cream.  

They analyzed records of individuals with biopsy-confirmed primary SCCis diagnosed between May 1, 2019, and April 30, 2020. Treatment involved 5-FU 5% cream and follow-up data documented disease status and treatment failure was defined as persistent or recurrent disease.  

The results showed that among 149 SCCis cases, 33.6% (50/149) occurred with immunosuppression. Treatment failed in 18 cases (10 persistent, 8 recurrent). The CCR was observed in 88.9% (128/144) of tumors <2 centimeters and 60.0% (3/5) of tumors ≥2 centimeters (P = .051). By treatment duration, CCR rates were 57.1% (4/7) for <2 weeks, 86.7% (72/83) for 2 to <4 weeks, and 93.2% (55/59) for ≥4 weeks (P = .019). Multivariate analysis linked treatment failure to shorter duration (odds ratio: 0.26; P = .007) and larger tumor size (odds ratio: 2.40; P = .037).  

Investigators concluded that shorter treatment and larger lesions predicted 5-FU failure in SSCis, while immunosuppression and location did not. 

Source: jaad.org/article/S0190-9622(24)03114-1/abstract