In four out of five cases, when breast cancer metastasizes to the eye, it spreads to the choroid, layers of blood vessels that nourish the back of the eye. However, breast cancer can also spread to the retina, the iris, and the optic nerve. Although the choroid is considered part of the central nervous system, it is more responsive to treatments such as chemotherapy, hormonal therapy and Herceptin than brain metastasis, probably because of the absence of the blood-brain barrier. Choroidal metastases usually develop late in the disease, and are more common in those with metastases to the lung or brain. Rarely, the choroid can be the first site of metastasis.
- Flashing lights
- Blind spot
- Floating spots (floatersâ€”a common condition in the adult population)
- Double vision
- Blurred vision
- Sensitivity to light
Most choroidal metastases have no symptoms and are found by a routine eye exam when the eyes are examined for glaucoma. A detached retina or a swollen optic nerve, can be a cause for concern. If your eye doctor thinks you might have choroidal metastases you should see an opthalmologist familiar with cancer complications, or if none is available, a retinal specialist (retinologist). Follow-up diagnostic tests will then be done to rule out other possible conditions. Once choroidal metastasis has been diagnosed, it is important to image the brain for metastatic involvement because brain metastasis commonly occurs at the same time.
Choroidal metastases without symptoms may just be watched. Often, they can be controlled by the treatments used to control disease in other organs, such as chemotherapy, hormonal therapy, and targeted therapies like Herceptin. But if symptoms are increasing and the tumor is threatening vision a radiation oncologist should be seen. External beam radiation (traditional type of radiation which is like a long x-ray) is used if there is more than one metastasis in one or both eyes and is quite effective. In one study it halted the loss of vision in 50% and improved it in 36% of patients. Brachytherapy or plaque radiotherapy can be used if there is only one metastasis. Both are methods that insert radioactive seeds or beads into the eye.
Mild side effects of external beam radiation, occurring 50% of the time, are conjunctivitis and erythema (skin redness and rash). Cataracts are also very common. Retinopathy, a much more serious side effect that may severely limit vision, occurs in 3-8%. Radiation retinopathy is said to be worse in those who have diabetes. It is also thought that using chemotherapy at the same time as radiation can worsen radiation-induced retinopathy. Treatment by laser can be used to manage retinopathy. There are reports that Avastin, an anti-cancer drug that inhibits tumor blood supply formation, can successfully treat complications like retinopathy and optic neuropathy, caused by radiation.
For more on Choroidal (eye) metastases, check the Selected Bibliography.