Topical 5-fluorouracil 1% for Moderate to Extensive Ocular Surface Squamous Neoplasia in 73 Consecutive Patients: Primary Versus Secondary Treatment

Importance Ocular surface squamous neoplasia (OSSN) is a spectrum of malignancies that generally includes conjunctival intraepithelial neoplasia (CIN) and squamous cell carcinoma (SCC). OSSN can be treated with topical therapies including interferon α-2b (IFN), mitomycin C (MMC), or 5-fluorouracil 1% (5FU). Recently, due to unavailability of IFN and toxicity associated with MMC, therapy has shifted towards 5FU. Objective Herein, we compare the use of 5FU 1% as a primary versus (vs) secondary treatment regimen in eyes with moderate to extensive OSSN. Design Setting and Participants Retrospective cohort study of 73 consecutive patients with unilateral moderate to extensive OSSN treated at a single tertiary ocular oncology center from 2016 to 2023. Mean follow up time was 478.2 days overall, with 283.0 days for primary 5FU group and 860.3 days for secondary 5FU group. Intervention Topical 5FU 1% 4 times daily for 2 weeks with option for 2-weekly extension until tumor control, either as primary treatment or as secondary treatment to surgical resection, topical IFN or topical MMC, or cryotherapy. Main Outcomes Outcome measures included tumor response, need for additional surgery, complications, and visual outcomes. Results A comparison (primary vs secondary treatment) revealed no difference in mean tumor basal dimension (19.6 vs 17.2mm, P = 0.46), thickness (3.7 vs 3.4mm, P = 0.64), or tumor extent (4.4 vs 4.5 clock hours, P = 0.92). The primary treatment group showed greater complete tumor control (77% vs 38%, P = 0.04). Multivariable analysis comparison (primary vs secondary treatment) showed primary treatment more likely to achieve complete tumor control (P = 0.01). There was no difference in the complication rate from 5FU treatment between the groups. There was no difference in visual outcome, and no tumor-related metastasis (0%) or death (0%). Conclusion and Relevance Topical 5FU 1% is efficacious and safe as a primary or secondary treatment for moderate to extensive OSSN. Tumors treated with primary 5FU 1% demonstrated more complete resolution. In patients with moderate to extensive OSSN, primary treatment with topical 5FU 1% may be warranted.