Malignant tumors can metastasize to the eye, just as they can metastasize to any other part of the body. The most common cancers that spread to the internal structures of the eye, originate in the breast, lung, prostate, or bone marrow (leukemia). Metastatic tumors within the eye are usually treated with systemic chemotherapy, targeting the origin of the cancer as well as the eye itself. Occasionally, radiation therapy has been used to treat the eye more directly.
However, the eye can also be the primary location for a cancerous tumor, the most common being choroidal malignant melanoma (see photo on the left). The average onset age for this type of melanoma is 55 or older and it appears that Caucasians are at highest risk of development.
What is a choroidal melanoma and how is it diagnosed?
Most people, today, are familiar with melanoma as the most dangerous type of skin cancer. Melanoma refers to cancer of the melanocytes, which are the cells responsible for giving skin color. Skin melanomas are associated with unprotected sun exposure, especially during youth. Choroidal melanomas, on the other hand, have not been linked to sun exposure, despite their increased occurrence in individuals with lighter skin. However, similar to skin cancer, intraocular melanomas are believed to arise from small benign pigmented areas called nevi and are best detected through pupil dilation and examination of the eye with special lenses. Photographs, including specialized digital imaging techniques, may be taken at each visit so that a patient’s progress can be visually documented, over time. If a pigmented area, within the eye, becomes larger and thicker, an ultrasound is usually performed to measure the area and check for suspicious characteristics.
How are choroidal melanomas treated?
In the past, the only treatment available for intraocular melanoma was removal of the eye. Today, amputation is usually unnecessary, as more advanced treatments are available. Currently, intraocular melanomas are treated with radioactive plaque therapy and transpupillary thermal therapy.
What is radioactive plaque therapy?
Radioactive plaque looks like a flattened gold penny with a centrally- located bump. The bump contains a small amount of radioactive iodine (I-125), which is shielded on three sides to ensure that the radioactivity is directed at the eye wall, specifically. In order to ensure a good fit, the retina specialist and radiation oncologist will size the plaque to each patient’s individual anatomy. The correctly sized and fitted plaque is then sewn onto the sclera (the white part) of the eye so that it lays over the tumor. After several days of localized radiation treatment, the plaque is removed. In the past 20 years, episcleral radioactive plaque therapy has become the most widely used treatment modality for choroidal malignant melanoma, obtaining a five- year survival rate of over 75%. Unfortunately, the advantages of plaque therapy are often negated by eye complications, which can develop as a result of it. These complications occur in over 20% of patients and include cataracts, radiation retinopathy, optic neuropathy, and neovascular glaucoma - all of which might impair ocular function.
To reduce the rate of secondary complications, we feel that intraocular tumors are best treated by a combined modality treatment. The series of treatments will begin with Transpupillary Thermotherapy (TTT). In TTT, a near-infrared 810 nm wavelength laser destroys cancerous cells by focusing a hot beam, of between 45 and 60 degrees C, on to the tumor. This precise method leaves the healthy tissue, surrounding the tumor, undisturbed. Using the 810 nm laser, we reduce the size of the lesion, over two treatment cycles, scheduled two weeks apart. Depending on the size of the tumor, additional treatments may be used. If the lesion has reduced to 3mm in height, an argon laser will be used; for lesions 3-12 mm in height, an I-125 plaque is used. And, if the tumor is anteriorly located, an excision of the affected area will most likely be performed. With the combined modality approach, total eradication of the tumor is possible, with a significant reduction in radiation-related complications due to lower dosages. To calculate the precise measure of radiation, we utilize the interactive treatment optimization program.
For further information, http://www.jhu.edu/wctb/coms/booklet/book2.htm