Radiation Therapy for Retinoblastoma
Retinoblastoma is a radiosensitive tumor, meaning it responds well to radiation therapy. Radiation helps destroy retinoblastoma tumors with minimal effect on a child’s vision. It is sometimes used in combination with chemotherapy or focal therapy to shrink tumors and kill cancer cells.
Because of its risk of long-term complications, however, it is usually avoided in children with retinoblastoma. When it is used, doctors at Hassenfeld Children’s Hospital at NYU Langone use targeted radiation to avoid damage to healthy tissue near the tumor. An anesthesiologist uses general anesthesia to help a child remain still during treatments.
Plaque Radiation Therapy
In plaque radiation therapy, radioactive “seeds” the size of grains of rice are placed on or near the tumor to deliver continuous, concentrated radiation while sparing other tissues in the eye. Also called brachytherapy, this treatment is typically used to treat small retinoblastomas located near the front of the eye or tumors that recur after other therapies.
Plaque radiation can destroy the tumor with little risk to the macula, the central part of the retina responsible for clear and defined vision.
First, an eye cancer specialist sews a small gold plaque, which is a bowl-shaped container filled with radioactive seeds, directly onto the eye beneath the tumor. This procedure requires two surgeries—one to implant the plaque on the eye and another to remove it. The plaque remains in the eye for five to seven days, and the child either stays in the hospital or at home during the treatment.
Because the radiation is applied near the lens of the eye, a cataract may form one to three years after treatment. Like cataracts in adults, this clouding of the lens caused by radiation is treatable in children.
Intensity Modulated Radiation Therapy
During intensity modulated radiation therapy, or IMRT, X-ray beams are adjusted to match the shape of the tumor. MRI scans help a doctor target the tumor, so that higher radiation doses can be delivered with minimal effect on nearby healthy tissue. Our radiation therapists use a linear accelerator, which generates high energy X-rays and directs them at the tumor.
With this treatment, the doctor adjusts the dose to deliver precise amounts of radiation based on computerized calculations of the tumor obtained through MRI. The procedure takes 20 to 30 minutes, 5 days a week.
Proton Beam Therapy
Proton beam therapy delivers high doses of focused radiation directly to the tumor without damaging surrounding tissue in the eye and brain. This is because proton radiotherapy involves a phenomenon called Bragg Peak, in which a burst of radiation energy is released only when it reaches the tumor or near it, even if it’s deep in the tissue.
Depending on the tumor’s type and size, this treatment can require daily 30- to 90-minute therapy sessions 5 days a week for several weeks. It can be used with chemotherapy to destroy cancer cells and avoid removal of the eye.
Managing Side Effects
Our doctors’ use of targeted radiation to treat retinoblastoma means that side effects are reduced. However, some children do experience side effects, depending on the radiation therapy and the location of the tumor. These can include a loss of eyelashes; fatigue; a sunburn-like redness of the skin around the eye; damage to the retina or optic nerve; cataracts; and irritation to the conjunctiva, the membrane that lines the eyelid and the white part of the eyeball. This appears like conjunctivitis or “pink eye.”
Your child’s oncologist and radiation oncologist work with nurses, social workers, and child psychologists to help your child and your family cope with the physical and emotional effects of radiation therapy.