Home » Texas Children’s Cancer Center sheds light on the treatment of retinoblastoma
Apr. 13, 2006 – Texas Children’s Hospital Press Release
By Laura Frnka
Texas Children’s Cancer Center, one of the largest pediatric cancer centers in the United States, is shedding light on the treatment of retinoblastoma – the most common malignant ocular tumor in childhood.
Affecting approximately one in 18,000 children under the age of 5, retinoblastoma can affect one eye, and in 20 percent to 30 percent of children, it can affect both eyes.
“As long as the disease has not spread beyond the eye, cure can be achieved in more than 90 percent of children through enucleation – or surgical removal of the eye,” said Dr. Murali Chintagumpala, clinical director of Texas Children’s Cancer Center brain tumor program and associate professor of pediatrics at Baylor College of Medicine. “This is the usual treatment for children with unilateral disease (a single eye affected) because they often present with advance disease with no hope for vision salvage.”
Chintagumpala says that one of the most difficult challenges of treating retinoblastoma is the presence of vitreous seeds – or pieces of tumor that have broken off from the original tumor and “float” in the eye. These vitreous seeds grow without a blood supply and are relatively inaccessible to chemotherapy agents.
A recent innovative trial at Texas Children’s Cancer Center used gene therapy to address the challenge of vitreous seeds.
The phase I trial consisted of incorporating the herpes simplex thymidine kinase gene into an adenoviral vector (AdV-TK) that has been engineered so it cannot replicate. The adenoviral vector carrying the herpes simplex thymidine kinase gene (AdV-TK) is injected intraocularly adjacent to the area with the vitreous seeds. The injection is followed 24 hours later by intravenous ganciclovir given twice a day for seven days.
Treatment is repeated one to four times depending on the response. In eight patients with one remaining eye (the other eye previously removed for progressive retinoblastoma) complicated by vitreous seeds, this approach was used. All patients had a response to therapy with no recurrences and one patient had no recurrence of vitreous seeds after more than three years of follow-up.
Inflammatory response to disintegrating tumor or the adenoviral vector injections resulted in a decrease in visual acuity in patients who received higher concentrations of the adenoviral vector. Most of these patients eventually had improved with visual acuity.
“It may be a promising approach to treat patients with vitreous seeds soon after diagnosis,” said Chintagumpala. “Further studies are under way to better delineate the role of this therapy in patients with retinoblastoma.”
Texas Children’s Cancer Center and Hematology Service is the largest pediatric cancer and blood disorder program in the United States. The Center sees patients from throughout the state of Texas and 35 other states and 26 countries. Nearly 25,000 patients will be seen in the Cancer Center’s outpatient clinic this year.