Iris melanoma relapsing sixteen years after proton-beam therapy: The importance of lifelong follow-up

Purpose: To report a case of locally recurrent spindle-cell iris amelanotic melanoma 16 years after proton-beam therapy. Observations: In 2001, a 45-year-old man presented with an amelanotic iris melanoma, extending from the 5 to 10 o'clock positions on his left eye. High-frequency ultrasonography showed extension of melanoma into the ciliary body. He was initially managed with proton-beam therapy (60 Gy delivered in four fractions over four consecutive days) and underwent ocular and systemic examination at regular intervals over the following years. Local tumor control was achieved, and the patient did not develop metastasis during sixteen consecutive years. In 2017, 16 years after he received proton-beam therapy, the patient developed a focal amelanotic lesion strongly suggestive of a local recurrence of iris melanoma, although it extended from the 1 to 6 o'clock positions. He also presented with treatment-resistant glaucoma with an intraocular pressure (IOP) of 37 mmHg, despite maximal topical IOP-lowering therapy. Since a second irradiation of the anterior segment was contraindicated, the eye was enucleated. Pathological analysis confirmed the diagnosis of iris melanoma and demonstrated iridocorneal angle invasion extending from the initial site to the recurrent tumor location. Conclusions and importance: Regular ophthalmological surveillance for life with gonioscopy and high-frequency ultrasonography is recommended in patients with iris melanoma, due to the possibility of delayed local recurrence more than a decade after the initial treatment. Keywords: Ciliary body, Iris, Melanoma, Radiotherapy, Irido-corneal angle, Proton-beam therap