Eye cancer is a relatively rare but varied group of malignancies that can arise from different parts of the eye. These cancers include uveal melanoma, the most common type in adults, as well as intraocular lymphoma and retinoblastoma, which primarily affects children. Treatment is highly individualized due to the delicate nature of the eye, requiring a multidisciplinary approach involving ophthalmologists, oncologists, and radiation specialists. The overall goal of any treatment strategy is two-fold: to eradicate the cancer and reduce the risk of it spreading while simultaneously attempting to preserve the patient’s vision and the physical structure of the eye.
Guiding Principles for Treatment Selection
A cancer care team determines the most appropriate course of treatment by weighing several factors. The two primary goals are patient survival and vision retention. The specific type of cancer is a major consideration, as a retinoblastoma requires a different approach than an intraocular melanoma. Tumor characteristics, such as size and exact location, are highly influential; a smaller, accessible tumor may be treated with localized therapy, while a large tumor or one near the optic nerve might require more aggressive intervention.
The patient’s overall health and age also influence the treatment plan. Furthermore, the tumor’s specific cell type, determined by a biopsy, guides the choice between radiation, surgery, or systemic drug therapy. Ultimately, the selection process involves a careful discussion of the benefits and potential side effects of each option.
Focused and Localized Treatment Options
Localized therapies are designed to deliver a high dose of treatment directly to the tumor site while sparing surrounding healthy tissue. This makes them ideal for smaller tumors.
Plaque Brachytherapy
The most common eye-sparing treatment is Plaque Brachytherapy. This involves temporarily placing a small, custom-made radioactive disc, or plaque, directly onto the outer wall of the eyeball over the tumor. This gold or lead-shielded plaque contains radioactive seeds, most commonly Iodine-125, that emit radiation over a short distance. The plaque is surgically sewn into place and remains on the eye for two to seven days, depending on the required radiation dose to destroy the cancer cells. Because the radiation is highly localized and shielded, it minimizes exposure to other parts of the eye. A second minor surgical procedure is performed to remove the plaque after the prescribed time.
Transpupillary Thermotherapy (TTT)
Another highly focused method is Transpupillary Thermotherapy (TTT), which utilizes an infrared diode laser to heat and destroy small tumors, such as choroidal melanomas or retinoblastomas. The laser light is delivered through a dilated pupil, slowly raising the temperature of the tumor cells to a level that kills them while limiting collateral damage. TTT can be used alone for very small, thin tumors, but it is often employed as an additional treatment after plaque brachytherapy.
Cryotherapy
Cryotherapy, or freezing therapy, is another localized technique primarily used for small tumors on the outer layers of the eye or as a supplement to other treatments. This method involves applying an extremely cold probe to the outside of the eye to destroy cancer cells through rapid freezing and slow thawing cycles. These localized treatments offer a high rate of tumor control and the best chance for maintaining vision and preserving the eye’s physical integrity.
External Radiation and Systemic Drug Therapies
External Beam Radiation Therapy (EBRT) delivers high-energy radiation from a machine outside the body. EBRT is often utilized for larger tumors or those located near sensitive structures like the optic nerve where plaque therapy is less suitable.
Proton Beam Therapy
Proton beam therapy is a specialized form of EBRT that uses positively charged particles instead of traditional X-rays. Protons release most of their energy at a precise, controlled depth, meaning they cause less damage to healthy tissue as they travel. For targeting, tiny metal clips, called tantalum markers, are surgically attached to the eye’s surface around the tumor.
Stereotactic Radiation
Stereotactic radiation therapy is another highly precise EBRT technique. It uses multiple small beams to deliver a high dose to the tumor, often delivered in one (radiosurgery) or a few (radiotherapy) sessions. These external methods are sometimes used for large uveal melanomas or cancers like intraocular lymphoma, often requiring daily treatments over a few days.
Systemic Drug Therapies, including chemotherapy and targeted therapy, are necessary when the cancer has spread beyond the eye or for specific types of eye cancer like intraocular lymphoma. Chemotherapy drugs may be given systemically through an intravenous infusion or injected directly into the eye to treat tumors like retinoblastoma. Targeted therapies work by blocking specific molecules within cancer cells, such as the CD20 protein in lymphoma or the BRAF protein in some melanomas, thereby stopping cancer growth. Immunotherapy drugs, such as Tebentafusp, are also used for advanced uveal melanoma by helping the body’s immune system recognize and attack the cancer cells.
Surgical Management of Eye Cancer
Surgical intervention focuses on the physical removal of the tumor or, in advanced cases, the entire eye. It serves as a primary treatment or a necessary step after other therapies fail.
Eye-sparing resections aim to remove the malignant tissue while preserving the globe’s structure. Procedures like iridectomy, which removes a part of the iris, or choroidectomy, which removes a portion of the choroid layer, are performed for small, localized tumors. These resections are challenging and typically reserved for highly specialized centers due to the risk of vision impairment.
When the tumor is large, has not responded to other treatments, or has caused significant vision loss, the complete removal of the eyeball, called enucleation, may be necessary. During enucleation, the surgeon removes the eyeball and replaces it with an orbital implant, often made of silicone or hydroxyapatite, which is attached to the eye muscles. This implant provides volume and allows for movement of the subsequent artificial eye, or prosthesis, which is custom-fitted by an ocularist several weeks after the surgery.