What is uveal melanoma?
Melanoma forms when melanocytes, the cells that make the pigment (melanin) in skin, hair, and eyes, undergo a transformation and become malignant. If melanoma arises in the uvea or uveal tract, one of the three layers of the wall of the eye, it is called uveal melanoma. The uvea is made up of the iris, the colored area at the front of the eye; the ciliary body, a ring of muscle tissue found behind the iris that changes the size of the pupil; and the choroid, a layer of blood vessels that bring oxygen and nutrients to the eye.
Tumors that arise in different parts of the uvea have different behaviors and outlooks. Melanomas in the iris are usually small, grow slowly, and rarely spread to other parts of the body. Melanomas in the ciliary body are often larger and more likely to spread to other parts of the body than those in the iris. The choroid is the most common site of uveal melanomas, and these tumors are also often larger and more likely to spread to other parts of the body than those in the iris.
Although uveal melanoma is rare, it is the most common eye cancer in adults. The disease is diagnosed mostly among older people, with a peak rate of diagnosis around 70 years of age. People who develop this cancer are likely to be Caucasian, fair-skinned, and have light-colored eyes.
What are the symptoms of uveal melanoma?
Uveal melanoma may have no early signs or symptoms, and it is sometimes found during an eye exam when ophthalmologists dilate the pupil to examine the inside of the eye. As the tumor grows it may cause symptoms including:
- Blurred vision or other change in vision
- Floaters (spots that drift in your field of vision) or flashes of light
- A dark spot on the iris
- A change in the size or shape of the pupil
- A change in the position of the eyeball in the eye socket
How is uveal melanoma diagnosed?
Ophthalmologists use several tests and procedures to diagnose uveal melanoma. To perform most of these tests they dilate or enlarge the pupil, which enables them to examine the inside of the eye. They may take pictures during these exams to help them track changes in the size of the tumor over time. These tests may include:
- Ophthalmoscopy: An exam using a small magnifying lens and a light to look at the inside of the eye.
- Slit-lamp biomicroscopy: An exam using a strong beam of light and a microscope to check the retina, optic nerve, and other parts of the eye.
- Gonioscopy: An exam of the front part of the eye between the cornea and iris.
- Ultrasound: An imaging test in which high-energy sound waves (ultrasound), are bounced off the internal tissues of the eye, to create an image of the inside of the eye.
- High-resolution ultrasound biomicroscopy: A higher-resolution ultrasound exam that creates a more detailed image than is possible with normal ultrasound.
- Transillumination of the globe and iris: An exam of the iris, cornea, lens, and ciliary body with a light placed on either the upper or lower lid.
- Fluorescein angiography: A examination of the blood vessels and the flow of blood inside the eye.
- Indocyanine green angiography: A procedure to find blocked or leaking blood vessels in the choroid layer of the eye.
- Uveal coherence tomography: An imaging test that uses light waves to detect swelling or fluid beneath the retina.
How is uveal melanoma treated?
Uveal melanoma has a high risk of migrating from the eye to other sites in the body, so ophthalmologists and oncologists treat this disease aggressively to try to prevent its spread. Treatment includes one or more of the following therapies:
Watchful Waiting: If a tumor shows no signs of growing, or if it is in the only eye with useful vision, ophthalmologists may closely monitor, but not treat, a patient until signs or symptoms appear or change. They will take pictures of the eye over time to keep track of changes in the size of the tumor and how fast it is growing.
Surgery: When treatment is required, surgery is the most common approach for uveal melanoma. The following types of surgery may be used:
- Resection: Surgery to remove the tumor and a small amount of healthy tissue around it.
- Enucleation: Surgery to remove the eye and part of the optic nerve.
- Exenteration: Surgery to remove the eye and eyelid, and muscles, nerves, and fat in the eye socket.
Radiation therapy: Radiation therapy uses high-energy x-rays or other types of radiation to kill cancer cells or keep them from growing. Ophthalmologists choose the most effective mode of delivering radiation therapy based on the type and stage of each patient’s melanoma. Radiation may be delivered to the tumor from an external or internal source.
- In external radiation therapy, radiation is generated by a machine outside the body and directed at the cancer. External radiation therapy includes:
- Charged-particle external beam radiation therapy, in which invisible particles called protons or helium ions are aimed at the cancer cells.
- Gamma Knife therapy, in which tightly focused gamma rays are directed at the tumor.
- In internal radiation therapy, a radioactive substance sealed in needles, seeds, wires, catheters, or disks is placed directly into or near the cancer. A commonly used form of internal radiation therapy in uveal melanoma is:
- Localized plaque radiation therapy, in which radioactive seeds are attached to one side of a disk, called a plaque, which is sewn directly on the outside wall of the eye with the seeds facing the tumor. The plaque is removed after several days.
Photocoagulation: In this procedure (also called light coagulation) ophthalmologists use laser light to destroy blood vessels bringing nutrients to the tumor, causing the tumor cells to die. Photocoagulation may be used to treat small tumors.
Thermotherapy: In thermotherapy heat from a laser destroys cancer cells and shrinks the tumor.
Are there experimental treatments for uveal melanoma?
Ophthalmologists are researching the effectiveness of targeted therapies for uveal melanoma. Among these is a therapy consisting of viral-nanoparticle conjugates that bind seek out and bind to cancer cells in the eye. (The therapeutic agent is administered through a vitreal injection into the eye.) When the drug is activated with an ophthalmic laser, it rapidly and specifically destroys the membranes of tumor cells while sparing key eye structures. This treatment approach has the potential to preserve patients’ vision.
What happens after treatment for uveal melanoma ends?
When melanoma spreads beyond its site of origin it is called metastatic (stage IV) melanoma. While many patients treated for uveal melanoma are free from the disease following treatment, about half will develop metastatic disease within 15 years of their original diagnosis. In 90% of these cases the melanoma spreads to the liver; less frequently it spreads to the lungs, bones, and brain. If metastatic disease is found early systemic treatment options may extend life expectancy and help improve quality of life for patients.
Because of the frequency of liver metastases, most the majority of surveillance techniques are focused on the liver. These liver-focused surveillance techniques include:
- Liver function tests
- Abdominal ultrasound
- Abdominal magnetic resonance imaging (MRI)
- CT scan
- PET scan