Retinoblastoma Flashcards
what causes retinoblastoma
biallelic loss of RB1 gene
what is the role of the Rb1 gene
- maintain genomic stability, epigenetic processes
what is the most common recurrent gene mutation in RB
BCOR (BCL6 corepressor)
what is the most common recurrent gain in RB?
myc-n amplification (still overall very rare)
what are the two main types of RB?
non-hereditary and hereditary
what is non-hereditary RB?
- due to a mutation in both alleles of a somatic cell
- median time to diagnosis of 30 months
- approx 75% of patients
what is hereditary RB?
due to germline biallelic inactivation of RB1, median time to diagnosis of 15 months
risk factors for developing RB
paternal exposure to welding fumes, ionizing radiation, working in the metal industry
presentation of RB
leukocoria (65-75%)
strabismus (10-15%)
nystagmus (5-10%)
how is RB staged
based on if there is extraretinal extension or extraocular disease (orbital or extra orbital)
general treatment options for RB
intra-arterial chemo
systemic chemo
focal therapies
RT
what systemic chemotherapy agents are used in RB
vincristine
carboplatin
etoposide
what intra-arterial chemo is used in RB
melphalan +/- carboplatin/topotecan
what focal therapies are used in RB
cryotherapy
thermotherapy
photocoagulation
can also use brachytherapy
when is enucleation indicated
always for group E disease (> 2/3 of globe filled with tumour, tumour in atnerior segment or ciliary body, invading iris)
what percent of unilateral vs bilateral RB have germline mutations?
unilateral - 15% have germline mutations
bilateral - 100% have germline
how do you perform surveillance for RB?
genetic testing of all family members (need sequencing) along with dilated eye exams q4wks in babies (while waiting for genetic results, and for those found to have germline RB1 inactivation)
what is most common SMN in RB patients?
25-40% are osteosarcoma (also soft tissue sarcomas, melanoma, lung cancer etc)
what is trilateral RB
asynchronous midline intracranial tumor, occurs in approx 5% of bilateral RB usually 2-3 yrs after diagnosis - need to screen with MRIs every 6 months
what defines group A tumour
small < 3mm, far from fovea and optic disk
what defines group B tumours
may be > 3mm but is confined to the retina
what defines group C tumours
local subretinal fluid or vitreous seeding
what defines group D tumours
diffuse subretinal fluid or seeding
what defines group E tumours
> 2/3 of globe filled with tumour
poor prognosis features - tumour in anterior segment, invasion of iris/cilary body
metastatic work up for RB
bone scan
bone marrows
CSF
MRI brain
