Radiation

Radiation therapy may be used to treat children with pediatric retinoblastoma. Radiation therapy involves high energy X-rays or other particles to slow the growth of cancer cells or kill them completely. Retinoblastoma radiation may be administered through techniques that involve external or internal radiation. The type of radiation therapy used will depend on several factors. Among the most important factors for determining the type of therapy are the size, location, and scope of the cancer.

External Beam Radiotherapy

External beam radiotherapy (EBRT) utilizes radiation from an outside source, as opposed to the internal radiation in brachytherapy. The process for external beam radiotherapy is similar to the process of having an X-ray taken. However, external beam radiotherapy is more intense. A typical EBRT treatment regimen consists of five days of treatment per week over the course of several weeks.
External beam radiotherapy is not as common as it used to be. This is because the procedure can be associated with severe side effects. For this reason, EBRT is currently used in cases where other treatments fail to control the retinoblastoma.

New External Radiation Techniques

Newer forms of external radiation are able to more precisely target the retinoblastoma tumors. This can help to reduce the amount of radiation exposure in the patient. Additionally, more targeted delivery of radiation means that lower doses of radiation can be given. This can help to reduce side effects from other techniques such as external beam radiotherapy.

Intensity Modulated Radiation Therapy

Intensity modulated radiation therapy (IMRT) allows medical professionals to aim radiation beams at the tumors. The beams may be administered at several different angles, as well as with different levels of strength and intensity. This can help to reduce the amount of radiation that reaches non-cancerous tissues.

Proton Beam Therapy

Proton beam therapy uses protons, or the positive component of atoms. Protons differ from X-rays in that they may be less destructive. X-rays release energy before and after reaching their intended target. This means that X-rays may damage non-cancerous tissue that must be passed through in order to reach the retinoblastoma tumor. However, protons release energy after traveling a certain distance. This may equate to less tissue damage in comparison to X-rays.

Internal Radiation Therapy

Internal radiation therapy is also referred to as brachytherapy or plaque radiotherapy. Internal radiation therapy is most commonly used for smaller tumors. A plaque containing small amounts of radioactive material is sewn directly onto the eyeball using tiny stitches. The plaque is a radiation carrier that resembles the shape of a very small bottle cap. It is made of lead or gold in order to shield other tissues from radiation. The plaque delivers radiation directly to the tumor for several days, after which time it is removed.

Radiation Side Effects

The majority of the side effects associated with radiation therapy arise from external beam radiation and other forms of external radiation. The most severe side effect is the risk of developing additional cancer in the treated area. This occurs from the radiation exposure during treatment. Internal radiation is not linked to the risk of developing additional cancer. However, internal radiation may cause damage to the optic nerve or retina. As a result, vision may be affected.

Other external radiation side effects may include:

• Cataracts, or clouding of the eye’s lens
• Damage to the optic nerve or retina
• Changes in the appearance of the eye over time