retinoblastoma

A cancer that starts in the retina.
It is the most common type of eye cancer in children.

(Causes)
The eyes start to develop well before birth. During the early stages of development, the eyes have retinoblasts (cells), that fill the retina with the new cells. Rarely, instead of maturing, some retinoblasts continue to grow out of control, forming a cancer (retinoblastoma). It is mostly due to a mutation in the RB1 gene, that helps keep cells from growing out of control.

(Types)
• congenital (heritable): One third of the cases. Abnormality in the RB1 gene. A germline mutation. Mostly, it occurs during early development, and only in a small portion, it is inherited from a parent. Usually, it develops bilateral retinoblastoma and multifocal retinoblastoma. Because all of the cells in the body have the mutated gene, these children also have a higher risk of developing cancers in other parts of the body. In addition to bilateral retinoblastoma, some children develop a brain tumor, usually in the pineal gland (pineoblastoma), know as trilateral retinoblastoma.
• sporadic (non-heritable): Two thirds of the cases. the abnormality in the RB1 gene develops in only one cell in one eye. develops only one tumor in one eye. often found when the child is slightly older . do not have the same increased risk of other cancers .

(Complications)
• glaucoma: If not treated, tumor cells can grow, fill much of the eyeball, break away from the retina, and reach other parts of the eye, forming more tumors. They might block the Schlemm's canal (tiny channel) located under the trabecular meshwork that let aqueous humour circulate into the bloodstream, raising the pressure inside the eye. It can lead to pain and loss of vision in the affected eye.
• metastasis: It can spread outside the eyeball. The cells sometimes grow through the sclera, cornea, eye socket, eyelids, and nearby tissues, and also grow along the optic nerve and reach the brain. Once the cancer is outside the eyeball, it can then spread to lymph nodes and to other organs such as the liver, bones, and bone marrow.

(Treatment)
• enucleation (surgery): Removal the whole eye, plus part of the optic nerve attached to it, when the vision is lost with no hope of getting it back. An orbital implant is usually done for the placement.
• radiation therapy: Uses high energy x-rays or particles to kill cancer cells.
- • external beam radiation therapy (EBRT): Focuses radiation beams from a source outside the body on the cancer.
- • intensity modulated radiation therapy (IMRT): The radiation beams at the tumor from several angles and can be adjusted the intensity to limit the dose reaching the nearby normal tissues.
- • brachytherapy (internal radiation therapy): A small amount of radioactive material (plaque) is placed on the outside of the part of the eyeball where the tumor is, and it stays there for several days. The plaque is made of gold or lead to shield nearby tissues from the radiation.
• laser therapy: Highly focused beams of light, that can heat and destroy body tissues.
- • laser photocoagulation: A laser beam, that aims through the pupil and focuses on the blood vessels that surround and supply the tumor, destroying them by heating them.
- • transpupillary thermal therapy: An infrared light (laser), that aims directly at the tumor to heat and kill the tumor cells. The temperatures are not quite as high as those used in laser photocoagulation, so some of the blood vessels on the retina may be spared.
• cryotherapy: Uses a small metal probe that is cooled to very low temperatures, killing the tumor cells.
• chemotherapy: Uses anti-cancer drugs.
- • systemic chemotherapy: Injects intravenously or by mouth. The drugs enter the bloodstream and reach throughout the body. E.g. carboplatin, vincristine, etoposide, cisplatin, cyclophosphamide, topotecan, doxorubicin.
- • intra-arterial chemotherapy: Injects directly into the ophthalmic artery.
- • intravitreal chemotherapy: Injects a drug directly into the vitreous humor. Typically melphalan or topotecan.

(Comparison)
• intraocular medulloepithelioma (diktyoma): A tumor arising mostly from primitive medullary epithelium in the ciliary body, rarely, from the optic nerve head or retina.
• ocular melanoma: A cancer that affects the eye. It is rare, but the most common primary cancer of the eye in adults. It arises mostly in the uveal tract.

• Category

  Retinoblastoma - Childhood