The combination of topotecan and vincristine for the
treatment of intraocular retinoblastoma in children resulted in a high rate of
response with manageable toxicity, according to the results of a prospective
phase 2 study.
Researchers chose to examine topotecan in this disease
state because of its efficacy on other central nervous system cancers, and the
similarities between the blood-brain barrier and the blood-ocular barrier.
The study included 27 patients with bilateral
retinoblastoma in at least one eye. The median age of patients was 8.1 months.
Treatment included topotecan started at a dose of 3
mg/m2 per day for 5 days. Dose was adjusted to meet a target
systemic exposure. Patients aged younger than 12 months received vincristine
0.05 mg/kg, while those older than 12 months received vincristine 1.5
mg/m2. All but one patient completed the entire course of therapy.
The median time required to complete the therapy was 47 days.
After treatment, 23 patients had sustained, confirmed
partial response in both eyes and one patient had a partial response in one
eye, for an overall response rate of 88.9% (95% CI, 71.3-96.9). All study
patients experienced hematologic toxicity during therapy. The toxicities
included grade-4 neutropenia (n=27), grade-3 anemia (n=19) and grade-3/grade-4
Although the study tested the combination of topotecan
and vincristine, the researchers said they “believe that most of the
observed response is due to topotecan.”
This data, which provides a toxicity profile of
topotecan in the youngest age group yet reported, should be helpful in guiding
treatment in patients of this age group, the researchers added.
- Qaddoumi I. Cancer. 2012;doi:10.1002/cncr.27563.