Evaluation of interferon alpha 2b as adjunctive therapy for conjunctival melanoma.

Purpose: Interferon alpha 2b (IFN-α2b) has been used as an adjunctive agent to treat conjunctival melanoma (CM), however its efficacy is unproved due to a paucity of data. We present 5 cases of incompletely excised CM lesions to inform clinical decision making regarding the adjunctive use of IFN-α2b.

Observations: We identified all biopsy proven CM cases treated between 1997 and 2017 at the University of Iowa. Of these, we analyzed cases in which topical IFN-α2b drops were prescribed after the initial excision to treat surgical margins that were positive for primary acquired melanosis [PAM] with or without atypia or invasive CM. We noted the origin of CM (nevus, PAM, or de novo), presence and location of margins positive for residual melanoma, duration of IFN-α2b treatment, recurrences, time to recurrence, and outcome at last follow-up. Topical IFN-α2b drops (1 million IU/mL 4 times daily for 3-6 months) were used as adjunctive therapy in 5 cases following incomplete surgical excision of CM. The preceding lesion was PAM in 4 cases and compound nevus in 1 case. In 2 cases, margins were positive for PAM with atypia and both resulted in remission of melanoma at 54 and 33 months, respectively. However, in 3 cases, margins were positive for invasive melanoma and all 3 developed recurrence of melanoma despite IFN-α2b use.

Conclusions And Importance: There are limited data regarding the efficacy of IFN-α2b as adjunctive therapy for incomplete excision of CM lesions. In this series, adjunctive topical IFN-α2b did not prevent recurrence in cases with surgical margins positive for invasive melanoma. Our results indicate that caution should be exercised when considering adjunctive IFN-α2b to treat CM lesions not excised completely.