Overall, about seven-in-ten patients can expect to live more than ten years after diagnosis and treatment of the ocular melanoma. The remainder will develop metastatic disease, which occurs when the ocular melanoma circulates through the body to form new tumors (‘metastases’) in other organs. Metastases usually develop many months or years after apparent good health and are only rarely detectable when the ocular tumor is diagnosed and treated.
Uveal melanomas metastasize through the blood circulation, almost always to the liver. Such ‘metastatic disease’ develops almost exclusively in patients whose tumor shows particular genetic abnormalities, such as loss of chromosome 3 (‘monosomy 3’), BAP1 deletion, and a class 2 gene expression profile. These abnormalities are detected by laboratory analysis of a tumor sample, which is obtained by biopsy If the eye is retained by means of radiotherapy or laser treatment. Life expectancy also depends on the tumor size, location and extent. Keeping the eye does not increase the risk of metastatic disease, as long as the tumor is successfully eradicated. Regular liver scans are usually performed to detect metastases before symptoms develop so as to maximize any chances of prolonging life. There are several kinds of treatment, which include systemic therapies as well as liver-directed therapies, such as tumor resection, chemo-embolization and hepatic perfusion. Unfortunately, once metastases develop, the prognosis is poor, although clinical trials are showing some promise.
Conjunctival melanomas are quite distinct from uveal melanomas, both genetically and in their metastatic behavior, resembling skin melanomas in these respects. Conjunctival melanomas can spread through lymph channels to glands in the neck or directly to other parts of the body. Metastatic disease is more likely to develop if the tumor is large or if it involves the eyelid conjunctiva or the caruncle. Metastases from conjunctival melanoma are more responsive to systemic therapy than uveal melanomas, especially if they show mutations of the BRAF gene. Impressive advances are occurring in this field.