Genetic Diagnosis of Retinoblastoma Using Aqueous Humour-Findings from an Extended Cohort.

The identification of somatic RB1 variation is crucial to confirm the heritability of retinoblastoma. We and others have previously shown that, when tumour DNA is unavailable, cell-free DNA (cfDNA) derived from aqueous humour (AH) can be used to identify somatic RB1 pathogenic variation. Here we report RB1 pathogenic variant detection, as well as cfDNA concentration in an extended cohort of 75 AH samples from 68 patients. We show cfDNA concentration is highly variable and significantly correlated with the collection point of the AH. Cell-free DNA concentrations above 5 pg/µL enabled the detection of 93% of known or expected RB1 pathogenic variants. In AH samples collected during intravitreal chemotherapy treatment (Tx), the yield of cfDNA above 5 pg/µL and subsequent variant detection was low (≤46%). However, AH collected by an anterior chamber tap after one to three cycles of primary chemotherapy (Dx1+) enabled the detection of 75% of expected pathogenic variants. Further limiting our analysis to Dx1+ samples taken after ≤2 cycles (Dx ≤ 2) provided measurable levels of cfDNA in all cases, and a subsequent variant detection rate of 95%. Early AH sampling is therefore likely to be important in maximising cfDNA concentration and the subsequent detection of somatic RB1 pathogenic variants in retinoblastoma patients undergoing conservative treatment.

Non-Invasive Prenatal Diagnosis of Retinoblastoma Inheritance by Combined Targeted Sequencing Strategies.

Retinoblastoma, the most common childhood eye cancer, presents in two forms: heritable or sporadic. Heritable retinoblastoma is caused by a germline mutation in the RB1 gene. Early diagnosis of children at risk of inheriting an RB1 mutation is crucial to achieve optimal clinical outcome. Currently, the majority of genetic testing is performed on newborns, which has multiple disadvantages for both families and the healthcare system. We have developed a non-invasive prenatal diagnosis (NIPD) service for retinoblastoma, available from 8 weeks' gestation, which uses a combination of massively parallel sequencing (MPS) techniques, dependent on the inheritance model. Detection of paternal or suspected de novo RB1 variants is achieved through amplicon-based MPS. NIPD of a fetus at risk of maternal inheritance is performed using capture-based targeted sequencing and relative haplotype dosage analysis. In addition, we show proof of principle of how capture-based sequencing can be used for de novo variants unsuitable for amplicon-based testing. In total, we report the NIPD of 15 pregnancies, results of which show 100% concordance with all postnatal testing performed at the time of publication (n = 12) with remaining pregnancies ongoing. NIPD of retinoblastoma therefore offers a viable alternative to newborn genetic testing.

Non-invasive diagnosis of retinoblastoma using cell-free DNA from aqueous humour.

Retinoblastoma is the most common eye malignancy in childhood caused by mutations in the RB1 gene. Both alleles of the RB1 gene must be mutated for tumour development. The initial RB1 mutation may be constitutional germline or somatic (originating in one retinal cell only). Distinguishing between these alternative mechanisms is crucial, with wider implications for management of the patient and family members. Bilateral retinoblastoma is nearly always due to a constitutional mutation; however, approximately 15% of unilateral cases also carry a germline mutation, and identifying these cases is important. This can be achieved by identifying both mutation types in tumour tissue and excluding their presence in blood. Modern eye-saving chemotherapy treatment (systemic, intra-arterial and intravitreal) has resulted in fewer enucleations. As a result, tumour tissue required to identify sporadic RB1 mutation(s) is not always available. Modern intravitreal chemotherapeutic techniques for retinoblastoma involve aspiration of aqueous humour (AH), providing a novel sample source for analysis. By analysing cell-free DNA present in the AH fluid of eyes affected with retinoblastoma, we have developed a screening test capable of detecting somatic RB1 mutations that is comparable to current tests on enucleated tumour tissue. The results obtained with fluid from enucleated eyes were concordant with tumour tissue in all 10 cases analysed. In addition, AH analysis from two patients undergoing intravitreal chemotherapy successfully identified somatic variants in both cases. Our findings suggest that AH fluid is a promising source of tumour-derived DNA in retinoblastoma for analysis.

Use of cyanoacrylate glue for temporary tarsorrhaphy in children.

PURPOSE: Congenital anophthalmia and postenucleation socket contracture are difficult conditions that require serial socket expansion with the use of hydrogel expanders and custom-made conformers along with temporary tarsorrhaphy. METHODS: The authors undertook a part prospective case review of all children undergoing temporary tarsorrhaphy using cyanoacrylate glue over a 3-year period at a tertiary specialist children's hospital. RESULTS: They report a series of 7 children undergoing temporary tarsorrhaphy with cyanoacrylate glue instead of the conventional suturing technique. Indications were socket expansion (n = 4), fornix deepening (n = 2), prosthesis reposition, and prolapsed conjunctiva following enucleation (n = 1).The age range was 3 weeks to 14 years (mean, 2.7 years). The glue tarsorrhaphy lasted between 0.5 and 13 weeks (mean, 4.5 weeks). There were no adverse outcomes, and the glue tarsorrhaphy was tolerated well in all cases, with relative ease of reapplication of glue in clinic. CONCLUSIONS: Their study demonstrates that this technique allows quick and efficient temporary tarsorrhaphy with relative ease of reapplication in a clinic setting, avoiding the need for multiple general anesthetics.