Abstract:  Objective To analyze the characteristics, treatment methods and outcomes of tumor recurrence during and after intra-arterial chemotherapy (IAC) for intraocular stage D of monocular retinoblastoma (RB), and to provide a reference for its treatment. Design Retrospective case series study. Participants A total of 26 children (26 eyes) with retinoblastoma (RB) who were diagnosed with intraocular stage D of monocular at Baoding Hospital of Beijing Children's Hospital and Beijing Children's Hospital from January 2020 to June 2023 were included. Methods All of them were treated with IAC. Based on the results of whole exome sequencing gene detection in peripheral blood, it is classified into hereditary RB and non-hereditary RB. Observe and record the recurrence of tumor lesions in the affected eyes of the children during and after treatment, and use Fisher's exact probability test to compare the differences between groups. Main Outcome Measures Time of tumour recurrence, location of the recurrence, method of treatment, and outcome of the treatment. Results Among the included patients, there were 6 cases (6 eyes) of hereditary RB and 20 cases (20 eyes) of non-hereditary RB. The average age at diagnosis was (20.12±9.11) months, and the follow-up period was 8 to 24 months. In the treatment of IAC, there were 3 cases of recurrence of hereditary RB and 1 case of non-hereditary RB, and there were significant statistical differences between the two groups (P=0.028). After treatment with IAC, there was no recurrence of hereditary RB, and 3 cases of non-hereditary RB recurred 5-10 months after treatment, with no statistically significant difference between the two groups (P=0.562). The recurrence of hereditary RB was all subretinal tumor implantation. Among them, 2 cases were stable after two IVC treatments, and 1 case was stable after two IVC treatments combined with two intravitreal injection chemotherapy. Among non-hereditary RB, one case developed localized subretinal tumor implantation during treatment and remained stable after continuing to receive two sessions of IAC combined with two sessions of intravitreal injection chemotherapy. One case had a recurrence of the primary tumor lesion after treatment and remained stable after receiving three more IAC treatments. One case had a recurrence of the primary tumor lesion after treatment, and the other case developed a subretinal tumor implantation lesion after treatment. The lesions of both children involved the optic nerve. After enucleation, no tumor metastasis was found during the follow-up. Conclusion Hereditary RB in the intraocular stage D of monocular is more likely to have tumor recurrence characterized by subretinal implantation during IAC treatment than non-hereditary RB. Genetic testing has guiding significance for the treatment of monocular retinoblastoma.  For hereditary RB in the intraocular stage D of monocular, to prevent recurrence during treatment, a sequential chemotherapy regimen of IAC combined with IVC can be adopted. 

Key words: Retinoblastoma, Intra-arterial chemotherapy, Genetic testing