Seasonal Variation in the Diagnosis of Retinoblastoma.

To determine the seasonal variation in the diagnosis of retinoblastoma in a global sample of children and to investigate predictors of seasonal trends. Data were collected through a global, multicenter, 1-year cross-sectional analysis that included all treatment- naïve retinoblastoma patients presenting to participating centers between January 1, 2017, and December 31, 2017. Due to variations in days per month, data were normalized to a 30-day/month calendar. Observed data were compared to a simulation study of expected results using a uniform distribution. Patient-level data were available for 4,351 children from 276 centers in 153 countries, of which 3,966 had a month of presentation recorded. There were relative peaks in disease presentation in January and July, with lower counts in November and December (p = .0015). No covariates were found to be significantly associated with the seasonal trend. Two covariates, patient age at presentation and extraocular tumor spread, showed a moderate association with month of presentation. Our findings suggest seasonal trends in the presentation of retinoblastoma across the world. However, these trends do not appear to be related to income level of a country, climate, or other covariates. Any connection between seasonal variation of retinoblastoma presentation and retinoblastoma outcomes remains unclear or not present.