Plaque Brachytherapy

Introduction

If you or a family member has been diagnosed with a tumour inside the eye — most often a uveal melanoma, sometimes a retinoblastoma in a child, or another less common intraocular tumour — plaque brachytherapy may have been raised as a treatment option. It is one of the main eye-preserving treatments used today, and for many patients it has replaced the older approach of removing the eye entirely.

This article explains what plaque brachytherapy is, how it works, what the procedure involves, what recovery looks like, and what to expect in the months and years afterwards. It is written for patients who already have a diagnosis and are now planning the next phase of care. Some of the details — particularly around vision outcomes and long-term follow-up — can feel heavy on first reading. You do not need to absorb everything at once. The aim is to give you a clear, plain-language picture so that the conversations with your ocular oncology team make more sense.

What Is Plaque Brachytherapy?

Plaque brachytherapy is a form of internal radiation treatment used for cancers and certain other tumours of the eye. The full clinical name is episcleral plaque brachytherapy. “Brachy” comes from the Greek word for “short,” and refers to the fact that the radiation source is placed at very short distance from the tumour — in this case, sitting directly on the outer surface of the eyeball.

The plaque itself is a small, curved metal disc, usually made of gold. It is shaped to fit the curve of the eye. Inside the plaque are tiny radioactive seeds. The gold shell directs the radiation forward, into the eye and the tumour, while shielding surrounding tissues such as the eyelids and the orbit. The most commonly used radioactive isotopes are iodine-125 and ruthenium-106. Palladium-103 is used in some centres. The choice of isotope depends on tumour thickness and the centre’s practice.

The plaque is surgically attached to the outside wall of the eye, directly over the tumour, in an operation performed under anaesthesia. It stays in place for a defined number of days — typically between three and seven, depending on the dose calculation — while it delivers the planned dose of radiation. It is then removed in a second short operation.

Unlike external beam radiation, where radiation is delivered from a machine outside the body, plaque brachytherapy delivers the dose from within millimetres of the tumour. This is what allows a high dose to be given to the cancer while limiting the dose to surrounding structures.

Why Is Plaque Brachytherapy Performed?

Plaque brachytherapy is used to treat tumours inside the eye. The most common indication is uveal melanoma, a cancer that arises from the pigment-producing cells of the uvea — the middle layer of the eye, which includes the iris, the ciliary body, and the choroid. Most uveal melanomas arise in the choroid, the layer between the retina and the white outer wall of the eye.

Other indications include:

• Retinoblastoma in selected cases, particularly when a small or medium tumour remains after, or recurs following, other treatments such as chemotherapy
• Vasoproliferative tumours of the retina
• Choroidal haemangioma in some cases, particularly when vision is threatened
• Selected metastatic tumours to the eye (cancers that have spread to the choroid from another organ), where local control is desired
• Conjunctival or iris melanoma in selected presentations, using modified plaque designs

The single largest body of evidence for plaque brachytherapy comes from uveal melanoma. The Collaborative Ocular Melanoma Study (COMS), a large multi-centre trial published in the late 1990s and early 2000s, compared plaque brachytherapy with surgical removal of the eye (enucleation) for medium-sized choroidal melanomas. It found no significant difference in overall survival between the two approaches. This is the central finding that changed practice: patients with medium-sized choroidal melanomas could keep their eye, with no measured cost in survival. Plaque brachytherapy then became the standard eye-preserving approach for these tumours in most ocular oncology centres.

Who Is a Candidate?

Whether plaque brachytherapy is suitable depends on several factors that your ocular oncology team will assess. These typically include:

• Tumour size and thickness. Plaque brachytherapy is most commonly used for small and medium-sized tumours. The American Brachytherapy Society (ABS) provides size guidance, and many centres treat tumours up to around 10 mm in thickness with plaques. Tumours that are very large or that fill much of the eye may not be controlled adequately by plaque alone, and other approaches may be considered.
• Tumour location. Tumours near the optic nerve or fovea (the central, high-resolution part of the retina) present a particular challenge because radiation in these areas has a higher risk of damaging vision. Some locations near the front of the eye can also be technically difficult to cover with a plaque.
• Extent of disease. If the tumour has extended outside the eye wall, or if there is widespread metastatic disease, treatment planning changes. Plaque brachytherapy is a local treatment and addresses only the tumour in the eye.
• General health and ability to undergo two short operations. The plaque has to be placed and then removed, both under anaesthesia.
• The patient’s own goals. Preserving the eye and any usable vision is a major reason patients choose plaque brachytherapy over enucleation. The likely vision outcome is part of the conversation.

For some patients, plaque brachytherapy is clearly the most appropriate option. For others, a careful comparison with alternatives is needed. The decision is made jointly with an ocular oncology team that typically includes an ocular oncologist, a radiation oncologist, and a medical physicist.

Alternatives

Several other treatments are used for intraocular tumours. Which alternatives are realistic depends on the diagnosis, the size and location of the tumour, and individual factors.

Observation

Some very small choroidal lesions that may or may not be melanoma are watched closely with photographs and ultrasound before any treatment is started. Observation is not appropriate once growth or other features of malignancy are confirmed in a tumour large enough to require treatment, but it is a real option for small, low-risk lesions.

External beam radiation: proton beam and stereotactic radiotherapy

Proton beam radiotherapy delivers focused external radiation using protons, which can be planned to stop within the tumour and limit dose to surrounding tissue. It is used at specialised centres for uveal melanoma and gives outcomes broadly comparable to plaque brachytherapy in published series. Stereotactic radiosurgery (for example, using a gamma knife or linear accelerator system) is another external beam option used in some centres. Availability of proton beam treatment is limited because it requires a dedicated facility.

Transpupillary thermotherapy (TTT)

TTT uses an infrared laser to heat and destroy small tumours through the pupil. It is sometimes used alone for very small tumours and is more often used in combination with plaque brachytherapy (“sandwich therapy”) for selected cases.

Local resection

In carefully selected cases, the tumour can be surgically removed from the eye wall while preserving the rest of the eye. This is technically demanding and offered in a smaller number of centres.

Enucleation

Enucleation is the surgical removal of the eye. It is used for very large tumours, tumours that have caused painful complications such as uncontrolled glaucoma, tumours with significant extension outside the eye, and in some cases where eye-preserving treatment is unlikely to maintain useful vision. An ocular prosthesis is fitted afterwards. The COMS trial established that for medium-sized choroidal melanomas, plaque brachytherapy and enucleation produce similar survival, which is why plaque brachytherapy is now widely offered as the eye-sparing alternative.

Systemic therapy

For uveal melanoma, systemic treatment is generally used for metastatic disease rather than as a first treatment of the eye tumour itself. For retinoblastoma, systemic chemotherapy (and intra-arterial or intravitreal chemotherapy in some centres) plays a central role, with plaque brachytherapy used as one of the local therapies.

Preparing for Plaque Brachytherapy

Preparation usually involves several appointments over a short period, sometimes condensed into a few days at a treating centre.

Confirming the diagnosis and staging

Before treatment is planned, the diagnosis and extent of disease are confirmed. Investigations typically include:

• Ophthalmic examination including dilated fundus examination, slit-lamp examination, and intraocular pressure
• Ultrasound of the eye (A-scan and B-scan) to measure tumour thickness and base dimensions
• Fundus photography and autofluorescence imaging
• Optical coherence tomography (OCT) to assess the retina
• Fluorescein and indocyanine green angiography in some cases
• Systemic imaging — commonly liver imaging and chest imaging for uveal melanoma, because the liver is the main site of distant spread
• Blood tests including liver function

Biopsy is not always required for choroidal melanoma; many diagnoses are made on imaging in experienced centres. In some cases, a fine-needle biopsy is taken at the time of plaque surgery for genetic and prognostic testing.

Treatment planning

Once the diagnosis and tumour dimensions are confirmed, a radiation oncologist and medical physicist plan the treatment. The plan specifies:

• The size and shape of the plaque (plaques come in various diameters and shapes; notched plaques are used for tumours near the optic nerve)
• The isotope and number of seeds
• The intended dose to the tumour apex (typically around 85 Gy for uveal melanoma, following ABS guidance)
• The duration the plaque needs to remain in place to deliver that dose

Practical preparation

Before admission you may be asked to:

• Pause certain blood-thinning medications, after checking with the prescribing doctor
• Stop eating and drinking for several hours before anaesthesia
• Arrange someone to accompany you and to help at home in the first days
• Bring eye drops, dark glasses, and comfortable clothing for the inpatient stay

Because the plaque is radioactive while it is in place, you will be told about radiation safety precautions during your hospital stay — for example, limits on close contact with young children and pregnant visitors. The team will explain these clearly.

What Happens During Plaque Brachytherapy

Plaque brachytherapy involves two short operations on the same eye, separated by the days during which the plaque is in place.

Operation 1: Placing the plaque

This operation is usually performed under general anaesthesia, though local anaesthesia with sedation is used in some cases. Typical steps:

1. The surgeon opens the conjunctiva (the clear membrane covering the white of the eye) to expose the sclera (the white outer wall).
2. If needed, one or more of the muscles that move the eye are temporarily detached so that the tumour area can be reached.
3. The tumour position is located precisely using transillumination (a bright light placed against the eye), indirect ophthalmoscopy, and sometimes intraoperative ultrasound. The position is marked on the sclera.
4. A non-radioactive dummy plaque may first be sutured into position to confirm correct placement.
5. The radioactive plaque is then sutured to the sclera directly over the tumour.
6. The muscles are reattached if they were moved, and the conjunctiva is closed over the plaque.
7. An eye pad and shield are placed.

While the plaque is in place

You will usually stay in hospital, in a designated room, for the days the plaque is in place — commonly 3 to 7 days. During this time the plaque delivers the planned dose. Most patients have moderate discomfort, a swollen eyelid, and a red eye, which are managed with pain relief and eye drops. Vision in the treated eye is often blurred from the dressing and the swelling, and a shield is worn. Specific instructions are given about radiation precautions, including how close visitors can come and for how long.

Operation 2: Removing the plaque

When the planned dose has been delivered, you return to the operating theatre. Under anaesthesia, the conjunctiva is reopened, the plaque is detached and removed, the eye muscles are reattached if needed, and the conjunctiva is closed. This operation is shorter than the first. After a period of recovery, most patients are discharged the same day or the day after.

Recovery and Healing

Recovery has an early phase, focused on the eye healing from the two operations, and a longer phase, focused on the response of the tumour and the late effects of radiation on the eye.

The first few weeks

In the first few days after the plaque is removed, the eye is typically:

• Red and swollen, particularly the eyelids
• Sore or aching, controlled with regular pain relief
• Sensitive to light
• Watering more than usual
• Blurred in vision

Eye drops — usually a combination of an antibiotic and a steroid drop — are prescribed for one to several weeks. Most people return to non-strenuous activities within one to two weeks. Heavy lifting, swimming, and contact sports are avoided for longer, as advised by the surgeon. Driving is resumed when vision in the better-seeing eye meets local legal standards and the operated eye is comfortable.

The first few months

The tumour does not disappear immediately. Over the first months, ultrasound measurements typically show gradual flattening of the tumour. Doctors look for shrinkage on imaging, changes in internal tumour reflectivity on ultrasound, and absence of growth as the main signs of response. Full flattening can take a year or more, and a residual scar in the choroid is normal.

Follow-up imaging and visits

Follow-up is lifelong. A typical pattern is examinations every few months for the first two years, then gradually less often. Each visit usually includes vision testing, eye examination, ultrasound, and photographs. For uveal melanoma, systemic surveillance (often liver imaging, sometimes liver function tests) is also performed at regular intervals, because the liver is the main site of distant spread. The schedule is tailored to your individual risk.

Risks and Complications

Plaque brachytherapy is generally well tolerated as a procedure, but radiation effects on the eye can develop over months and years. It is helpful to separate early surgical risks from longer-term radiation effects.

Early surgical risks

• Pain, swelling, and bruising around the eye
• Bleeding under the conjunctiva (subconjunctival haemorrhage), which usually resolves on its own
• Strabismus or double vision if eye muscles are detached and reattached, usually temporary but occasionally persistent
• Infection, which is uncommon
• Slippage or misplacement of the plaque, which is uncommon in experienced centres because intraoperative checks are used
• Anaesthetic risks, similar to other short operations

Longer-term radiation effects

• Radiation retinopathy — damage to the small blood vessels of the retina, which can reduce vision. It is one of the most common late effects.
• Radiation optic neuropathy — damage to the optic nerve, particularly when the tumour was close to the nerve. It can cause significant vision loss.
• Maculopathy — damage to the central retina, with reduced reading and detailed vision.
• Cataract — clouding of the lens, which can be addressed later with cataract surgery if it affects vision.
• Dry eye and surface problems
• Neovascular glaucoma — new abnormal vessels can develop and raise eye pressure, sometimes painfully. In severe cases this can lead to loss of the eye despite tumour control.
• Vitreous haemorrhage
• Scleral thinning at the treatment site

The risk of any one of these is shaped by tumour size, tumour location (especially proximity to the optic nerve and fovea), the dose plan, and individual factors. Some risks can be reduced or treated. Anti-VEGF injections into the eye, focal laser, and steroids are used to manage radiation retinopathy and maculopathy in many centres, although none completely prevent damage.

Tumour recurrence

Local recurrence — regrowth of the tumour in or around the original site — happens in a minority of patients. When it occurs, options may include repeat plaque, other forms of radiation, transpupillary thermotherapy, or enucleation, depending on the situation.

Distant spread (metastasis)

For uveal melanoma, distant spread is the most serious long-term risk and the reason for ongoing systemic surveillance. The liver is the most common site. Metastatic risk is influenced by tumour size, cell type, location, and increasingly by genetic testing of the tumour (such as gene expression profiling or chromosome 3 status). Plaque brachytherapy controls the eye tumour but does not change the risk of spread that was already present at diagnosis. This is why the COMS trial found similar survival for plaque brachytherapy and enucleation: removing the eye does not remove cells that may have already spread.

Life After Plaque Brachytherapy

Vision in the treated eye

What happens to vision in the treated eye varies widely. Some patients keep useful vision in that eye for many years; others lose central vision but retain peripheral vision; a smaller number eventually lose useful vision in the treated eye altogether. The main factors are how close the tumour was to the optic nerve and fovea, the tumour size, and the development of radiation complications. Your team can give you a more personalised picture once the tumour position and dose plan are known.

Vision in the other eye and daily life

Because the other eye is generally healthy, most patients continue with everyday activities — reading, working, driving (where legal vision standards are met), and household tasks. Adjusting to changes in depth perception or to reduced vision on one side takes time and is helped by low-vision rehabilitation when needed. Sunglasses and protective eyewear are commonly recommended to protect the better-seeing eye.

Emotional impact

A diagnosis of eye cancer and the experience of treatment can be emotionally difficult. Worry about recurrence, about vision, and about long-term outlook is common, particularly around follow-up appointments. Many patients find it helpful to talk with a counsellor or to connect with patient support groups for ocular melanoma or retinoblastoma. Letting your team know about anxiety, sleep difficulties, or low mood is part of holistic follow-up care.

Work, travel, and activity

Once the eye has healed, there are usually no fixed restrictions on travel or most activities. Air travel is normally fine after the early healing period. Contact sports and activities with risk of eye injury may need eye protection, particularly for the better-seeing eye. Your surgeon will advise based on your individual situation.

Plaque Brachytherapy in Children

In children, the main use of plaque brachytherapy is for retinoblastoma, a cancer of the retina that most often affects children under the age of five. Retinoblastoma treatment has changed considerably in recent decades. The mainstays now include systemic chemotherapy, intra-arterial chemotherapy (where chemotherapy is delivered directly into the artery supplying the eye), intravitreal chemotherapy for vitreous seeds, focal therapies such as laser and cryotherapy, and, in selected situations, plaque brachytherapy.

Plaque brachytherapy in retinoblastoma is generally considered for:

• A single tumour or small group of tumours that have not been fully controlled by chemotherapy and focal therapy
• Localised recurrence after other treatments
• Selected tumours where focal treatment alone is unlikely to be enough but the eye can still be preserved

The technique is similar to that in adults, adapted for the small eye of a child, and is performed under general anaesthesia. Special attention is given to long-term effects, because children have many years ahead of them in which late radiation effects can develop, and some children with heritable retinoblastoma have an increased lifetime risk of certain other cancers. Retinoblastoma management is highly specialised and is carried out in dedicated paediatric ocular oncology centres, with close coordination between paediatric oncologists, ocular oncologists, and the family.

For children with other rare intraocular tumours, the use of plaque brachytherapy is decided case by case.

Frequently Asked Questions

How long does the whole treatment take from start to finish?

From admission for the first operation to discharge after plaque removal is usually about one week, with some variation either side depending on the planned dose and the centre’s practice. Pre-treatment workup may add a few days to a couple of weeks, depending on how quickly investigations are arranged.

Will I be radioactive after the plaque is removed?

No. The radioactive source is inside the plaque, and once the plaque is taken out, you are no longer giving off radiation. The precautions you follow while the plaque is in place do not apply afterwards.

Will I keep useful vision in the treated eye?

This depends mostly on where the tumour is in the eye. Tumours far from the optic nerve and fovea generally have a better chance of keeping useful vision. Tumours close to these structures carry a higher risk of vision loss over time. Your ocular oncology team can give you a more specific answer based on your scans and treatment plan.

Is the procedure painful?

The operations themselves are done under anaesthesia, so you do not feel them. Afterwards, most people have moderate eye soreness, a sense of pressure, and discomfort from the swollen eyelid, which are managed with pain relief and eye drops. Severe pain is uncommon and should be reported to your team.

How does plaque brachytherapy compare with proton beam radiation?

Both are radiation treatments that aim to control the tumour while preserving the eye. Published outcomes for tumour control and survival are broadly similar. Choice between them often depends on tumour size, location, and the availability of proton beam facilities, which are limited. Some tumours that are difficult to cover with a plaque — for example, very large tumours or tumours right at the edge of the optic nerve — may be treated more easily with proton beam. Your ocular oncology team will discuss what is realistic in your situation.

Why was a biopsy not taken before treatment?

For many choroidal melanomas, the diagnosis can be made confidently on imaging by an experienced ocular oncologist, without a biopsy. When biopsy is needed — for diagnostic uncertainty or for prognostic genetic testing — it is often performed at the time of plaque placement, so that a separate procedure is not required.

Will I need follow-up forever?

Yes. Lifelong follow-up is standard for uveal melanoma and other intraocular cancers, both to monitor the treated eye and to watch for any sign of distant spread. The frequency of visits gradually decreases over the years, but follow-up does not stop.

Can plaque brachytherapy be repeated if the tumour comes back?

In selected cases of local recurrence, a second plaque can be considered. Other options include other forms of radiation, transpupillary thermotherapy, or enucleation. The right choice depends on the size, location, and behaviour of the recurrence.

What does the COMS trial mean for me?

The Collaborative Ocular Melanoma Study found that for medium-sized choroidal melanomas, survival was similar whether the eye was treated with plaque brachytherapy or removed. For many patients, this was the evidence that allowed eye-preserving treatment to become standard. It does not mean every patient with eye melanoma should have plaque brachytherapy — some tumours are too large, too advanced, or in positions where eye-preserving treatment is unlikely to give a useful result. The decision is still individual.

Conclusion

Plaque brachytherapy has changed what eye cancer treatment looks like. For many patients with uveal melanoma and for selected patients with retinoblastoma and other intraocular tumours, it offers a way to treat the tumour while keeping the eye, with outcomes that are broadly comparable to removing the eye for medium-sized tumours. The trade-off is the possibility of long-term radiation effects on vision, which the team works to minimise through careful planning and active treatment of complications as they arise.

Treatment is one step in a longer journey that includes pre-treatment imaging and planning, two short operations a few days apart, weeks of early healing, and years of follow-up for both the eye and the rest of the body. Understanding the shape of that journey — what is straightforward, what is uncertain, and what is in your team’s hands rather than yours — is part of preparing well. The conversations with your ocular oncology team, informed by your own questions, are where the individual treatment decisions are made.