Radiation Therapy for Eye Cancer: Options, Process & Risks

TL;DR

• Radiation therapy uses high‑energy beams to destroy eye‑cancer cells while sparing surrounding tissue.
• Three main modalities are used: brachytherapy (plaque), proton therapy, and external‑beam radiotherapy.
• Choice depends on tumor size, location, patient age, and equipment availability.
• Treatment usually lasts 3‑7 days, followed by a gradual visual recovery period.
• Common side effects include dry eye, cataract formation, and temporary vision changes; most are manageable.

When doctors talk about radiation therapya medical treatment that delivers controlled doses of ionizing radiation to kill cancer cells, they’re referring to a tool that can target tumors inside the eye without removing the organ. Eye cancerany malignant growth that originates in ocular structures such as the retina, choroid, or ciliary body is rare, but when it occurs, preserving vision becomes a top priority. This article explains how radiation therapy works for eye cancer, walks through the main techniques, and shows what patients can expect before, during, and after treatment.

How Radiation Therapy Eliminates Cancer Cells

The core idea is simple: high‑energy particles or photons damage the DNA inside tumor cells, preventing them from dividing. Normal cells can repair this damage better than cancer cells, so the net effect is tumor shrinkage with limited collateral injury. Modern machines deliver radiation with sub‑millimeter precision, guided by imaging (CT, MRI, or ultrasound) that maps the exact shape of the tumor.

Key attributes of a radiation plan include:

• Energy type - photons, protons, or radioactive isotopes.
• Dose - measured in Gray (Gy), often split into multiple fractions.
• Target margin - a small safety buffer (usually 1-2mm) around the tumor.

These parameters are tailored by a radiation oncologista physician who designs and oversees radiation treatment plans together with a multidisciplinary team that may include ophthalmologists, medical physicists, and dosimetrists.

Radiation Modalities Used for Eye Cancer

Three techniques dominate the landscape in 2025:

Brachytherapy (Plaque Therapy)

Brachytherapy places a small, sealed plaque containing radioactive iodine‑125 or ruthenium‑106 directly on the sclera (the white of the eye). The plaque stays in place for 3‑7 days, delivering a high dose to the tumor while the rest of the eye gets far less exposure.

Typical attributes:

• Energy source: Low‑energy gamma or beta emitters.
• Typical dose: 70‑100Gy total.
• Best for: Small‑to‑medium choroidal melanomas (≤10mm basal diameter).

Proton Therapy

Proton therapy uses positively charged protons accelerated to high speeds. Because protons stop at a precise depth (the Bragg peak), they spare tissue beyond the tumor, making this method ideal for lesions close to the optic nerve or macula.

Typical attributes:

• Energy source: High‑energy protons (70-250MeV).
• Typical dose: 50‑70Gy delivered in 4‑5 fractions.
• Best for: Large or juxtapapillary melanomas, and cases where preserving central vision is critical.

External‑Beam Radiotherapy (EBRT)

EBRT directs photon beams from a linear accelerator (LINAC) at the eye. Advanced techniques such as intensity‑modulated radiotherapy (IMRT) or stereotactic radiosurgery (SRS) shape the beam to match the tumor contour.

Typical attributes:

• Energy source: High‑energy X‑rays (6‑15MV).
• Typical dose: 40‑60Gy in fractions of 2Gy.
• Best for: Patients without access to a proton center and for tumors that are not ideal for plaque placement.

Choosing the Right Modality - Decision Criteria

Doctors weigh several factors before recommending a specific type:

In short, small peripheral tumors often go with brachytherapy, large posterior lesions lean toward proton therapy, and EBRT serves as an accessible fallback.

Step‑by‑Step: What Happens During Treatment

1. Simulation & Planning: A CT or MRI scan captures the eye’s anatomy. The radiation oncologist, together with a medical physicist, draws a 3‑D contour of the tumor and critical structures (optic nerve, lens).
2. Custom Device Creation (if needed): For plaque therapy, a custom‑shaped silicone insert holds the radioactive seeds. For proton therapy, a patient‑specific aperture is milled.
3. Positioning & Immobilization: The patient rests on a chin‑rest with a bite‑block or a customized mask to keep the eye perfectly still.
4. Delivery: Depending on modality, the radiation is emitted for a few minutes (EBRT/SRS) or the plaque remains surgically attached for several days (brachytherapy). Proton sessions last ~5‑10 minutes each.
5. Post‑Treatment Monitoring: Follow‑up visits at 1month, 3months, then every 6months for at least 5years. Imaging checks tumor regression and eye health.

Managing Side Effects - What to Expect

Because the eye is delicate, even precise radiation can cause short‑ and long‑term changes. Common issues include:

• Dry eye - due to reduced tear production; artificial tears and punctal plugs help.
• Cataract formation - especially with plaque therapy; surgery is often required later.
• Radiation retinopathy - delayed vascular damage; treated with anti‑VEGF injections.
• Vision fluctuations - many patients notice blurry vision for weeks; improves as swelling subsides.

Early referral to an ocular oncologist and a low‑vision specialist can preserve quality of life. Lifestyle tweaks-protecting the eyes from bright light, using sunglasses with UV protection, and maintaining good blood pressure-also reduce risk.

Outcomes & Prognosis

When radiation therapy is applied appropriately, local control rates exceed 90% for most ocular melanomas. Studies from the International Ophthalmic Oncology Society (2023) show a 5‑year eye‑preservation rate of 78% for plaque therapy and 84% for proton therapy. Visual acuity after treatment depends heavily on tumor location; tumors away from the macula often retain 20/40 vision or better.

Importantly, radiation does not replace systemic chemotherapy for metastatic disease. If the cancer spreads beyond the eye, a multidisciplinary approach-including immunotherapy agents like pembrolizumab-becomes necessary.

Frequently Asked Questions

Understanding the role of radiation therapy eye cancer helps patients weigh benefits against risks and choose a path that aligns with their visual goals. With modern imaging, precise delivery, and supportive eye‑care, radiation remains the cornerstone of curative treatment for most eye‑based malignancies.