RT Journal Article SR Electronic T1 Retinoblastoma seeds: impact on American Joint Committee on Cancer clinical staging JF British Journal of Ophthalmology JO Br J Ophthalmol FD BMJ Publishing Group Ltd. SP 127 OP 132 DO 10.1136/bjophthalmol-2021-318892 VO 107 IS 1 A1 Ankit Singh Tomar A1 Paul T Finger A1 Brenda Gallie A1 Tero Kivelä A1 Ashwin Mallipatna A1 Chengyue Zhang A1 Junyang Zhao A1 Matthew Wilson A1 Rachel Brennan A1 Michala Burges A1 Jonathan Kim A1 Jesse L Berry A1 Rima Jubran A1 Vikas Khetan A1 Suganeswari Ganeshan A1 Andrey Yarovoy A1 Vera Yarovaya A1 Elena Kotova A1 Denis Volodin A1 Yacoub Yousef A1 Kalle Nummi A1 Tatiana L Ushakova A1 Olga V Yugay A1 Vladimir G Polyakov A1 Marco Antonio Ramirez-Ortiz A1 Elizabeth Esparza-Aguiar A1 Guillermo L Chantada A1 Paula Schaiquevich A1 Adriana C Fandiño A1 Jason C Yam A1 Winnie W Lau A1 Carol P Lam A1 Phillipa Sharwood A1 Sonia Moorthy A1 Quah Boon Long A1 Vera Adobea Essuman A1 Lorna A Renner A1 Ekaterina Semenova A1 Jaume Català-Mora A1 Maria Correa Llano A1 Elisa Carreras A1 , YR 2023 UL http://bjo.bmj.com/content/107/1/127.abstract AB Aim To investigate whether the American Joint Committee on Cancer (AJCC) clinical category cT2b needs to be subclassified by the type and distribution of retinoblastoma (RB) seeding.Methods Multicentre, international registry-based data were collected from RB centres enrolled between January 2001 and December 2013. 1054 RB eyes with vitreous or subretinal seeds from 18 ophthalmic oncology centres, in 13 countries within six continents were analysed. Local treatment failure was defined as the use of secondary enucleation or external beam radiation therapy (EBRT) and was estimated with the Kaplan-Meier method.Results Clinical category cT2b included 1054 eyes. Median age at presentation was 16.0 months. Of these, 428 (40.6%) eyes were salvaged, and 430 (40.8%) were treated with primary and 196 (18.6%) with secondary enucleation. Of the 592 eyes that had complete data for globe salvage analysis, the distribution of seeds was focal in 143 (24.2%) and diffuse in 449 (75.8%). The 5-year Kaplan-Meier cumulative globe-salvage (without EBRT) was 78% and 49% for eyes with focal and diffuse RB seeding, respectively. Cox proportional hazards regression analysis confirmed a higher local treatment failure risk with diffuse seeds as compared with focal seeds (hazard rate: 2.8; p<0.001). There was insufficient evidence to prove or disprove an association between vitreous seed type and local treatment failure risk(p=0.06).Conclusion This international, multicentre, registry-based analysis of RB eyes affirmed that eyes with diffuse intraocular distribution of RB seeds at diagnosis had a higher risk of local treatment failure when compared with focal seeds. Subclassification of AJCC RB category cT2b into focal vs diffuse seeds will improve prognostication for eye salvage.Data are available on reasonable request. All data relevant to the study are included in the article or uploaded as online supplemental information.