Plaque brachytherapy is a specialized form of radiation treatment used primarily for certain cancers located within the eye. This highly targeted approach delivers a concentrated dose of radiation directly to the tumor while aiming to spare surrounding healthy tissues. It offers a precise method for managing ocular malignancies, working to preserve the eye’s structure and function.
How Plaque Brachytherapy Works
Plaque brachytherapy involves two primary components that work together to deliver precise radiation. The “plaque” is a small, custom-designed applicator, often shaped like a shallow dish and typically made from gold. This gold material serves a dual purpose: it acts as a rigid carrier for the radioactive sources and also functions as a shield, preventing radiation from spreading extensively into healthy parts of the eye and surrounding orbital tissues.
The “brachytherapy” aspect refers to “short-distance therapy,” meaning the radioactive source is placed directly on or very close to the tumor. Small, radioactive “seeds” are precisely arranged within the gold plaque. Common radioactive isotopes used for these seeds include Iodine-125, Palladium-103, or Ruthenium-106, each chosen based on the tumor’s characteristics and location. These seeds continuously emit radiation over a specific period, directly irradiating the cancerous cells.
The design of the plaque and the selection of the isotope ensure that a high dose of radiation is delivered to the tumor. The gold shielding helps to protect the delicate structures nearby, such as the optic nerve and the macula, which are responsible for vision. This localized delivery minimizes the exposure of healthy tissue to radiation, reducing the potential for widespread damage. The focused radiation works to destroy the tumor cells by damaging their DNA, preventing them from growing and dividing.
The Treatment Process
The treatment process begins with detailed planning. Specialized imaging techniques, such as ocular ultrasound and magnetic resonance imaging (MRI) or computed tomography (CT) scans, are used to precisely map the tumor’s size, shape, and location within the eye. This information is then used by a team of specialists, including ophthalmologists and radiation oncologists, to custom-design the gold plaque and calculate the exact radiation dose needed to effectively treat the tumor.
The first surgical procedure involves its implantation. Under general anesthesia, the surgeon carefully attaches the custom-fitted plaque to the outer surface of the eye, known as the sclera, directly over the tumor. Fine sutures are used to secure the plaque in place, ensuring it remains in the precise position to deliver the radiation accurately.
Following the implantation surgery, the patient typically remains in the hospital for several days while the plaque delivers its therapeutic radiation dose. The duration of this period varies, usually ranging from two to seven days, depending on the type of radioactive seeds used and the prescribed radiation dose. During this time, precautions are taken to ensure the safety of both the patient and healthcare providers, as the plaque continuously emits radiation.
After the predetermined radiation dose has been delivered, a second surgical procedure is performed to remove the plaque. This removal surgery also takes place under local or general anesthesia and involves detaching the plaque from the sclera. Once the plaque is removed, the radiation treatment is complete, and the patient can typically return home shortly thereafter to begin the recovery phase.
Recovery and Potential Side Effects
After the plaque removal surgery, patients can expect some immediate recovery from the procedure itself. An eye patch may be worn for a short period, and discomfort, mild swelling, or bruising around the eye are common. Patients are typically prescribed eye drops, including antibiotics to prevent infection and anti-inflammatory medications to reduce swelling and pain. Regular follow-up appointments are scheduled to monitor the eye’s healing and the tumor’s response.
Beyond the surgical recovery, the radiation delivered by the plaque can lead to potential long-term side effects that develop over months or even years. These effects stem from the radiation’s impact on healthy eye tissues that were within the treatment field. One common concern is radiation retinopathy, which is damage to the blood vessels in the retina, potentially leading to blurred or decreased vision. The severity of retinopathy can vary widely, sometimes requiring additional treatments.
Cataracts, a clouding of the eye’s natural lens, are another frequent long-term complication of radiation to the eye. This condition can cause blurry vision and may eventually require surgical removal and lens replacement. Dry eye syndrome, characterized by insufficient tear production, can also occur, leading to irritation, redness, and a gritty sensation. These symptoms can often be managed with lubricating eye drops.
The extent of vision changes or potential vision loss is highly dependent on the tumor’s size, its exact location relative to the optic nerve and macula, and the total radiation dose delivered. Tumors closer to these central vision structures carry a higher risk of affecting sight. While efforts are made to shield healthy tissues, some degree of radiation exposure to these sensitive areas is often unavoidable.
Treatment Effectiveness and Goals
Plaque brachytherapy serves several primary objectives in the management of eye cancer. The foremost goal is to achieve local tumor control, meaning to destroy the cancerous cells within the eye. This treatment has demonstrated high success rates in eliminating the tumor, with studies reporting local control rates often exceeding 90% for appropriately selected cases. This effectiveness makes it a preferred option for many patients.
Another objective of plaque brachytherapy is to preserve the eye itself, thereby avoiding enucleation, which is the surgical removal of the eye. For many patients, retaining their natural eye, even if vision is compromised, is a significant consideration. Plaque brachytherapy allows for targeted treatment that often successfully eradicates the tumor while maintaining the eye’s structure.
A third goal is to preserve as much useful vision as possible. This outcome is more variable and depends heavily on the tumor’s initial size and its proximity to the optic nerve and the macula, the part of the retina responsible for sharp, central vision. Tumors located far from these areas generally have a better prognosis for vision preservation compared to those situated closer. The ability to achieve these combined goals makes plaque brachytherapy a valuable treatment choice for many individuals facing eye cancer.