Purpose: To study the factors influencing the response to treatment with interferon alfa 2b (IFN) in ocular surface squamous neoplasia (OSSN)

Methods: Retrospective study of 91 patients

Results: The mean age at presentation of patients with OSSN was 58 years (median, 60 years; range, 21 to 83 years). The mean number of clock hours of conjunctiva/cornea/limbus involvement by the tumor was 6 (median, 6; range, 1 to 12). The mean duration of topical IFN was 3 months (median, 3 months; range, 1 to 6 months) and the mean number of subconjunctival injections of IFN was 2 (median, 2; range, 0 to 6), till complete tumor regression or initiation of alternate treatment. Of 91 OSSN cases treated with IFN, 72 (79%) patients showed complete response to treatment, while 19 (21%) showed partial response displaying mean % tumor reduction of 34% (median, 20%; range, 5% to 90%). Patient demographics, immune status, disease chronicity, tumor location, or morphological pattern were not predictive of tumor response to IFN. The only factor predictive of incomplete response of OSSN to IFN was more than 6 clock hour involvement of ocular surface by OSSN (p = .04). Of 31 (34%) cases with OSSN >6 clock hours, 23 (74%) patients showed complete tumor regression with IFN alone, while 8 (26%) patients displayed incomplete response; and of 60 (66%) cases with OSSN ≤6 clock hours, 49 (82%) patients showed complete tumor regression with IFN alone, while 11 (18%) patients displayed incomplete response. Tumor recurrence was noted in 3% cases and one case had corneal perforation secondary to infective keratitis over a mean follow-up period of 14 months (median, 8 months; range, 3 to 58 months).

Conclusion: Clock hour involvement of ocular surface by OSSN determines the response to IFN. Interferon alfa 2b is an effective immunotherapy agent for tumors ≤6 clock hours of ocular surface in 82% cases and serves as an immunoreducing agent for larger tumors involving >6 clock hours of ocular surface in 26% cases.