Environmental and Occupational Risk Factors for Retinoblastoma.

Introduction: The Wisconsin Department of Health Services received notice of an unusual number of cases of retinoblastoma in a small geographic area. Retinoblastoma is a rare pediatric eye cancer that strikes children aged <5 years. The reporters of these cases were concerned that they may be part of a cancer cluster. Cancer clusters are unusual numbers of cases in a defined geographic area over a defined period of time. They are believed to be caused by shared environmental or occupational risk factors. It is not known to what extent these risk factors play a role in retinoblastoma incidence. Methods: As part of state standard operating procedures for cancer cluster investigations, Wisconsin Department of Health Services performed a scan of the scientific literature to determine what is known about environmental or occupational risk factors in an attempt to consider the likelihood that the observed cases could be attributed to a shared community factor. Throughout this process, over 1,200 abstracts were scanned, and 41 papers were read in depth. This narrative review is the result of that literature review surrounding such risk factors and retinoblastoma incidence. Results: Although much is known about the genetic abnormalities that result in tumor development, little is known about environmental and occupational risk factors and the potential roles they play in retinoblastoma development. Few studies have been found, and those that are published are often hampered by small numbers owing to the rarity of this cancer. Although some studies have shown potential correlations between exposures and incidence, these results need to be corroborated by other studies. This review unfortunately did not provide direction for continuing an inquiry into the potential cluster of cases, and the cancer cluster investigation that precipitated this review was closed. Discussion: Like all rare cancers, progress toward understanding the root cause(s) of retinoblastoma is difficult because of the small number of cases per year. Still, future studies should continue to add to the body of knowledge about environmental and occupational risk factors for this pediatric cancer, so that the weight of collective studies can inform future prevention and treatment efforts.