When breast cancer spreads beyond its original site, it is known as metastatic breast cancer. While it can travel to various parts of the body, its appearance in the eye, called ocular metastasis, is less frequent. The development of cancer in the eye is a sign that the disease has become widespread. Understanding how this happens, what signs to look for, and the ways it is diagnosed and managed is important for patients and their families.
How Breast Cancer Spreads to the Eye
Metastasis begins when cancer cells detach from the primary tumor in the breast and enter the bloodstream or lymphatic system. These circulatory pathways allow the cells to travel to distant locations and form new tumors. The eye, with its intricate network of blood vessels, is one of these potential destinations.
The part of the eye most often affected is the choroid, a layer filled with blood vessels between the retina and the sclera (the white of the eye). This rich blood supply makes the choroid a common site for cancer cells to lodge and grow. The choroid is involved in up to 81% of ocular metastasis cases.
While the choroid is the most common location, cancer cells can also affect other parts of the eye. These include the orbit (the bony socket), the iris (the colored part of the eye), the ciliary body, and the optic nerve. The specific type of breast cancer can influence this likelihood, as invasive lobular carcinoma has a higher tendency for ocular metastasis than invasive ductal carcinoma.
Symptoms of Ocular Metastasis
The signs of breast cancer in the eye can vary, and some people may not notice any symptoms. When symptoms do appear, they often involve changes in vision. A common complaint is blurry or decreased vision, especially if a tumor affects the macula, the part of the retina for sharp, central vision.
Other visual disturbances include seeing floaters, which are small dark spots or lines drifting across the field of vision. Some people experience flashes of light (photopsia). If a tumor is on the iris, a visible spot or color change may be noticeable. A shadow in the field of vision or changes in pupil shape are also possible.
Eye pain can occur, but many ocular metastases are painless. Persistent redness or double vision (diplopia) can also be indicators. If the metastasis is in the orbit, the eye may bulge forward (proptosis) or appear sunken (enophthalmos). Since these symptoms can be caused by other eye conditions, a prompt examination by an ophthalmologist is necessary for a diagnosis.
The Diagnostic Process
Diagnosing ocular metastasis starts with a patient history and a comprehensive eye examination. An ophthalmologist will perform a dilated eye exam, using drops to widen the pupil for a clear view of the back of the eye. This allows for inspection of the retina, optic nerve, and the choroid, where tumors often appear as creamy-yellow, plateau-shaped lesions.
To get a detailed look at the eye’s internal structures, an ophthalmologist may use several imaging techniques:
- Ocular ultrasound (B-scan) uses sound waves to create an image of the inside of the eye, helping to determine a tumor’s size and shape.
- Optical coherence tomography (OCT) is a non-invasive test providing high-resolution images of the retina to detect fluid or changes in its layers.
- Fundus photography documents the tumor’s appearance over time.
- Fluorescein angiography involves injecting a dye into the bloodstream to photograph its circulation, which helps characterize a lesion’s blood flow.
A biopsy of the eye is often not needed if the patient has a known history of metastatic cancer. Systemic imaging, such as CT, MRI, or PET scans, may also be performed to check for metastasis elsewhere in the body.
Treatment Approaches
Managing breast cancer that has spread to the eye has two primary goals: controlling the cancer throughout the body and preserving as much vision as possible. Treatment plans are developed by a team including a medical oncologist, a radiation oncologist, and an ophthalmologist. The approach is tailored to the individual’s cancer type, extent of metastasis, and overall health.
Local therapies focus directly on the eye tumor. The most common treatment is external beam radiation therapy (EBRT), which uses high-energy rays to destroy cancer cells. EBRT is effective at shrinking the tumor, relieving symptoms, and preserving vision, and is delivered in sessions over several weeks.
Because eye metastasis indicates widespread disease, systemic therapies are a core part of treatment. The choice depends on the primary breast cancer’s characteristics:
- Hormone therapies are used for hormone receptor-positive (ER/PR-positive) breast cancer to block or lower estrogen levels.
- Targeted therapies are a mainstay for HER2-positive breast cancer, attacking the HER2 protein on cancer cells.
- Chemotherapy may be used for various types of breast cancer, especially if it is aggressive or has spread to multiple organs.
If an eye tumor grows despite systemic therapy, the treatment plan may need to be changed.
Managing Vision and Prognosis
Ocular metastasis indicates that the breast cancer is advanced. While the prognosis was historically poor, advancements in systemic therapies have improved the outlook for many patients, allowing them to live longer with a better quality of life. The mean survival time after a diagnosis of orbital metastases from breast cancer is approximately 22 months.
Managing the impact on vision is a key part of care, as some vision loss may be permanent. This can result from the tumor or from treatment side effects like radiation retinopathy or dry eye. Low-vision aids, such as magnifiers and specialized glasses, can help patients make the most of their remaining vision.
A collaborative care team ensures that both the systemic cancer and ocular symptoms are managed concurrently. Support services, including counseling and patient support groups, can provide valuable emotional and practical assistance. Long-term management focuses on controlling the disease, maximizing visual function, and maintaining the best possible quality of life.