Retinoblastoma

According to the Children’s Oncology Group, Retinoblastoma is a rare cancer, occurring in about one in 20,000 children. It originates in a part of the eye called the retina. The retina is a thin layer of nerve tissue that coats the back of the eye, which allows a person to see. Retinoblasts (immature cells of the retina) multiply during gestation and early life, to make enough cells to create the retina. As children age, the cells mature and are no longer able to divide and multiply, a process called differentiation1.

 

Staging of Retinoblastoma

 

The following stages are used for retinoblastoma:

Intraocular retinoblastoma

In intraocular retinoblastoma, cancer is found in the eye and may be only in the retina or may also be in other parts of the eye such as the choroid, ciliary body, or part of the optic nerve. Cancer has not spread to tissues around the outside of the eye or to other parts of the body.

Extraocular retinoblastoma

In extraocular (metastatic) retinoblastoma, cancer has spread beyond the eye. It may be found in tissues around the eye or it may have spread to the central nervous system (brain and spinal cord) or to other parts of the body such as the bone marrow or lymph nodes.

 

Treatment of Retinoblastoma

 

Six types of standard treatment are used:

Enucleation

Enucleation is surgery to remove the eye and part of the optic nerve. The eye will be checked with a microscope to see if there are any signs that the cancer is likely to spread to other parts of the body. This is done if the tumor is large and there is little or no chance that vision can be saved. The patient will be fitted for an artificial eye after this surgery. Close follow-up is needed for 2 years or more to check the other eye and to check for signs of recurrence in the area around the eye.

Radiation therapy

Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells or keep them from growing. There are two types of radiation therapy. External radiation therapy uses a machine outside the body to send radiation toward the cancer. Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, plaques, or catheters that are placed directly into or near the cancer. The way the radiation therapy is given depends on the type and stage of the cancer being treated. Methods of radiation therapy used to treat retinoblastoma include the following:

  • Intensity-modulated radiation therapy (IMRT): A type of 3-dimensional (3-D) radiation therapy that uses a computer to make pictures of the size and shape of the tumor. Thin beams of radiation of different intensities (strengths) are aimed at the tumor from many angles. This type of radiation therapy causes less damage to healthy tissue near the tumor.
  • Stereotactic radiation therapy: Radiation therapy that uses a rigid head frame attached to the skull to aim high-dose radiation beams directly at the tumors, causing less damage to nearby healthy tissue. It is also called stereotactic external-beam radiation and stereotaxic radiation therapy.
  • Proton beam radiation therapy: Radiation therapy that uses protons made by a special machine. A proton is a type of high-energy radiation that is different from an x-ray.
  • Plaque radiotherapy: Radioactive seeds are attached to one side of a disk, called a plaque, and placed directly on the outside wall of the eye near the tumor. The side of the plaque with the seeds on it faces the eyeball, aiming radiation at the tumor. The plaque helps protect other nearby tissue from the radiation.

Cryotherapy

Cryotherapy is a treatment that uses an instrument to freeze and destroy abnormal tissue, such as carcinoma in situ. This type of treatment is also called cryosurgery.

Thermotherapy

Thermotherapy is the use of heat to destroy cancer cells. Thermotherapy may be given using a laser beam aimed through the dilated pupil or onto the outside of the eyeball, or using ultrasound, microwaves, or infrared radiation (light that cannot be seen but can be felt as heat). Thermotherapy may be used alone for small tumors or combined with chemotherapy for larger tumors.

Chemotherapy

Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. When chemotherapy is taken by mouth or injected into a vein or muscle, the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy). When chemotherapy is placed directly into the cerebrospinal fluid, an organ (such as the eye), or a body cavity such as the abdomen, the drugs mainly affect cancer cells in those areas (regional chemotherapy). The way the chemotherapy is given depends on the type and stage of the cancer being treated.

A form of chemotherapy called chemoreduction is used to treat retinoblastoma. Chemoreduction reduces the size of the tumor so it may be treated with local treatment (such as radiation therapy, cryotherapy, or thermotherapy).

 

New types of treatment are being tested in clinical trials.

 

  • Subtenon chemotherapy
  • Ophthalmic arterial infusion therapy
  • High-dose chemotherapy with stem cell rescue
  • Biologic therapy2

Search for clinical trials in Georgia.

1Adapted from the Children’s Oncology Group (COG): http://www.curesearch.org/for_parents_and_families/newlydiagnosed/article.aspx?ArticleId=3127&StageId=1&TopicId=1&Level=1. (Accessed July 2016)

2Adapted from the National Cancer Institute's PDQ Database: http://www.cancer.gov/cancertopics/pdq/treatment/retinoblastoma/Patient. (Accessed July 2016)