Abstract
Purpose :
There are currently no molecular biomarkers in clinical practice for retinoblastoma (RB), because direct tumor biopsy is prohibited. In low-income countries including India, retinoblastoma mostly present with evident advanced disease, clinically detected with proptosis or a fungating mass and is associated with more than 50% mortality. Patients with post-laminar optic nerve invasion (PLONI) and deep choroid invasion (DCI) features are considered to be at higher risk of metastatic tumor spread. We propose this prospective study to evaluate the validity of CSF based liquid biopsy as a potential surrogate biopsy site for detection of metastatic disease for prognostication and treatment decision. This study aim to detect cell free tumor DNA (ctDNA) and identify the specific RB1 mutations that underlie tumorigenesis from the cerebral spinal fluid (CSF) and discuss the validity and clinical utility of the platform.
Methods :
Subjects included 1 RB patients with at least 12 months of follow-up. Cerebrospinal fluid (CSF) collected by spinal tap, done as part of the metastatic workup protocol for all extraocular retinoblastoma patients. Cell-free DNA (cfDNA) was isolated from CSF and sequenced to assess mutation in RB1 gene. Results were compared to peripheral blood RB1 testing.
Results :
We detected non germ line mutation in cfDNA from blood of unilateral retinoblastoma patient with intra-ocular disease at presentation and during post treatment extraocular tumor recurrence. Same mutation was identified from cfDNA of blood during tumor recurrence also found from CSF of same patient indicating the presence of tumor DNA in the blood and CSF.Conventional CSF cytology was negative for tumor cells during tumor recurrence. Patient eventually developed overt CNS metastasis during follow up and succumbed to the disease.
Conclusions :
This study demonstrates feasibility, safety, and utility of CSF based liquid biopsy for early detection of CNS metastasis of RB before conventional cytology can provide the diagnosis.. The results from this study will help in prognostication and risk stratification of patients into high-risk category for metastasis and hence need for more aggressive treatment.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.