Retinoblastoma (Rb) is the most common primary intraocular malignancy of childhood, but an uncommon paediatric cancer, with a constant incidence worldwide of 1:15,000-1:20,000 live births. Despite its rarity, Rb has served as a cornerstone in the field of oncology in many of the aspects that comprise cancer management, including classification schemes, treatment modalities, genetic testing and screening. Until just over half a century ago, the major treatment for Rb was eye removal, and prognosis was poor with outcome fatal for most children. The dramatic evolution, in a short period of time across all fields of Rb management, as well as the development of specialized centres, better infrastructure and introduction of awareness campaigns, has resulted in nearly 100% survival in developed countries and allowed eye salvage in many of the cases. External beam radiotherapy was used as the main treatment choice for four decades, but replaced by chemotherapy at the turn of the century. Initially, and still in many centres, chemotherapy is administered intravenously, but recently is targeted directly into the eye by means of intra-ophthalmic artery and intravitreal chemotherapy. To date, a range of treatments is available to the Rb expert, including enucleation, but there is lack of consensus in a number of scenarios as to what to use and when. In such a rare cancer, treatment outcomes are reported usually via retrospective analyses, with few prospective randomized controlled trials. Classification schemes have also evolved following the introduction of new treatment modalities, but discrepancies exist among centres with respect to the preferred schema and its interpretation. Retinoblastoma management is a remarkable success story, but the future will require a collaborative effort in the form of multicentre randomized controlled trials in order to further improve the quality of care for this subset of young children with ocular cancer.

Global Retinoblastoma Study Group IMPORTANCE Early diagnosis of retinoblastoma, the most common intraocular cancer, can save both a child's life and vision. However, anecdotal evidence suggests that many children across the world are diagnosed late. To our knowledge, the clinical presentation of retinoblastoma has never been assessed on a global scale.OBJECTIVES To report the retinoblastoma stage at diagnosis in patients across the world during a single year, to investigate associations between clinical variables and national income level, and to investigate risk factors for advanced disease at diagnosis. DESIGN, SETTING, AND PARTICIPANTSA total of 278 retinoblastoma treatment centers were recruited from June 2017 through December 2018 to participate in a cross-sectional analysis of treatment-naive patients with retinoblastoma who were diagnosed in 2017. MAIN OUTCOMES AND MEASURESAge at presentation, proportion of familial history of retinoblastoma, and tumor stage and metastasis. RESULTSThe cohort included 4351 new patients from 153 countries; the median age at diagnosis was 30.5 (interquartile range, 18.3-45.9) months, and 1976 patients (45.4%) were female. Most patients (n = 3685 [84.7%]) were from low-and middle-income countries (LMICs). Globally, the most common indication for referral was leukocoria (n = 2638 [62.8%]), followed by strabismus (n = 429 [10.2%]) and proptosis (n = 309 [7.4%]). Patients from high-income countries (HICs) were diagnosed at a median age of 14.1 months, with 656 of 666 (98.5%) patients having intraocular retinoblastoma and 2 (0.3%) having metastasis. Patients from low-income countries were diagnosed at a median age of 30.5 months, with 256 of 521 (49.1%) having extraocular retinoblastoma and 94 of 498 (18.9%) having metastasis. Lower national income level was associated with older presentation age, higher proportion of locally advanced disease and distant metastasis, and smaller proportion of familial history of retinoblastoma. Advanced disease at diagnosis was more common in LMICs even after adjusting for age (odds ratio for low-income countries vs upper-middle-income countries and HICs, 17.92 [95% CI,, and for lower-middle-income countries vs upper-middle-income countries and HICs, 5.74 [95% CI,). CONCLUSIONS AND RELEVANCEThis study is estimated to have included more than half of all new retinoblastoma cases worldwide in 2017. Children from LMICs, where the main global retinoblastoma burden lies, presented at an older age with more advanced disease and demonstrated a smaller proportion of familial history of retinoblastoma, likely because many do not reach a childbearing age. Given that retinoblastoma is curable, these data are concerning and mandate intervention at national and international levels. Further studies are needed to investigate factors, other than age at presentation, that may be associated with advanced disease in LMICs.