Abstract
Purpose:
Vitreous seeds in retinoblastoma have clinical heterogeneity and we have previously proposed a classification to distinguish between them. This study evaluates the clinical characteristics of the three vitreous seed classes: dust (class 1), spheres (class 2) and clouds (class 3) and their responses to intravitreal melphalan.
Methods:
Bi-institutional cohort study of 87 patient eyes that received 475 intravitreal injections of melphalan (median dose 30µg) given weekly, a median of 5 times (range 1-12). At presentation, the vitreous seeds were classified into three groups: dust, spheres and clouds. Indirect ophthalmoscopy, fundus photography, ultrasonography and ultrasonic biomicroscopy were used to evaluate clinical response to weekly intravitreal melphalan injections and time to regression of vitreous seeds. Kaplan-Meier estimates of time to regression, ocular, patient and event-free survival were calculated and Log-rank test of curve comparison.
Results:
There was a significant difference in time to regression for the three seed classes (p<0.0001): the median time to regression was 0.6 months, 1.7 months and 7.7 months for dust, spheres and clouds, respectively. Dust received significantly fewer injections, a lower median and cumulative dose of melphalan; while clouds received significantly more injections, a higher median and cumulative dose of melphalan. Kaplan-Meier estimates for two-year ocular, patient, and event-free survival (related to target seeds) was not significantly different between the three seed groups: overall, they were 90.4% (95% confidence interval (CI) 79.7-95.6), 100%, 98.5% (95%CI 90-99.7), respectively.
Conclusions:
The three vitreous seed classes have a significantly different time to regression in response to intravitreal melphalan. The vitreous seed classification can help to predict time to regression, number, median dose and cumulative dose of intravitreal melphalan injections required.