Oncologic and visual outcomes after postoperative proton therapy of localized conjunctival melanomas

INTRODUCTION: conjunctival melanomas have high local relapse rates. Oncologic and visual outcomes can be improved with proton therapy and no-touch surgery. MATERIAL AND METHODS: a monocentric retrospective study of consecutive patients treated with surgery and proton therapy for conjunctival melanoma was conducted. Proton therapy was performed to a total dose of 45 Grays physical dose delivered in eight fractions over two weeks. RESULTS: Ninety-two patients were included. The mean age was 63-year-old. 65.2% of patients had primary acquired melanosis. The mean tumor thickness and diameter was 2.5 mm and 7.0 mm respectively. The clinical stage was T1 in 71.6% of cases, with a quadrangular involvement of more than 90° in 69% of cases. Conjunctival melanomas were of epithelioid cell-type in 40% of cases. Mean follow-up was 4.7 years. Five-year local failure rate was 33.2%. Of 25 local recurrences, 14 were marginal/out-of-field, 4 in-field, others were undetermined. First surgery at expert center resulted in 24.3% of local failure at 5 years versus 38.7% if performed elsewhere (p = 0.41). Salvage exenteration was performed in 13 patients. Tumor stage and quadrangular involvement were significant factors for local failure. Five-year progression-free survival and cause-specific death rates were 61.5 and 3.6%. Stage and epithelioid type were associated with poorer progression-free survival. Trophic toxicity occurred in 22.9% of patients and was treated locally, with grafts in 7 patients. Glaucoma and cataract occurred in 13 and 22 patients respectively. Prognostic factors for visual deterioration were age, tumor extent (multifocality, quadrangular involvement > 180°) and cryotherapy. CONCLUSIONS: 5-year local failure rate after postoperative proton therapy for conjunctival melanoma was of 33.2%. Radiation-induced complications were overall manageable.