Uveal melanoma

Uveal melanoma is cancer (melanoma) of the eye involving the iris, ciliary body, or choroid (collectively referred to as the uvea) with advanced tumors encompassing more than one of these structures. Tumors arise from the pigment cells (melanocytes) that give color to the eye. Uveal melanoma is distinct from most skin melanomas associated with ultraviolet exposure; however, it shares several similarities with other non-sun-exposed melanomas.

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Incidence of uveal melanoma is highest among people with lighter skin and blue eyes. Other risk factors, such as blue light exposure and arc welding have been put forward, but are still debated in the field. The size of the tumor tends to double yearly creating pressure in the eye and often impairing peripheral vision.

Treatment

The treatment protocol for uveal melanoma has been directed by many clinical studies, the most important being "The Collaborative Ocular Melanoma Study" (COMS).The treatment varies depending upon many factors, chief among them, the size of the tumour.

Primary treatment can involve removal of the affected eye (enucleation); however, this is now reserved for cases of extreme tumor burden or other secondary problems. Advances in radiation therapies have significantly decreased the number of patients treated by enucleation in developed countries.

The most common radiation treatment is plaque brachytherapy, in which a small disc-shaped shield (plaque) encasing radioactive seeds (most often Iodine-125, though Ruthenium-106 and Palladium-103 can also be used) is attached to the outside surface of the eye, overlying the tumor. The plaque is left in place for a few days and then removed.There is no difference in risk of metastasis between enucleation and plaque radiotherapy.

Other modalities of treatment include transpupillary thermotherapy, external beam proton therapy, resection of the tumor, or a combination of different modalities. Different surgical resection techniques can include trans-scleral partial choroidectomy, and transretinal endorescetion.

Prognosis

The primary site of metastasis for uveal melanoma is the liver in most patients, less likely the lungs. Approximately 50% of patients will develop metastases within 15 years after treatment of the primary tumor. The average survival time after diagnosis of liver metastases is 8 to 10 months.