The retinoblastoma-predisposition gene, RB1, segregates as an autosomal dominant trait with high (90%) penetrance. Certain families, however, show an unusual low-penetrance phenotype with many individuals being unaffected, unilaterally affected, or with evidence of spontaneously regressed tumors. We have used single-strand conformation polymorphism analysis and PCR sequencing to study two such families. Mutations were found in exon 20 of RB1 in both cases. In one family a C----T transition in codon 661 converts an arginine (CGG) to a tryptophan (TGG) codon. In this family, incomplete penetrance and mild phenotypic expression were observed in virtually all patients, possibly indicating that single amino acid changes may modify protein structure/function such that tumorigenesis is not inevitable. In the second family the mutation in codon 675 is a G----T transversion that converts a glutamine (GAA) to a stop (TAA) codon. However, this mutation also occurs near a potential cryptic splice acceptor site, raising the possibility of alternative splicing resulting in a less severely disrupted protein.

Background: Retinoblastoma (RB) is a malignant, childhood tumour of the developing retina that occurs with an estimated frequency of 1 in 20 000. Identification of oncogenic mutations in the RB1 gene aids in the clinical management of families with a heritable predisposition to RB. Here we present the spectrum of genetic and epigenetic changes identified in 194 tumours and 209 blood samples, from 403 unrelated RB patients. Methods: Mutation screening was carried out across all 27 RB1 exons and their associated splice sites. Small coding sequence changes were detected using fluorescent conformation analysis followed by sequencing. Large exonic deletions were detected by quantitative fluorescent PCR. Methylation specific PCR of the RB1 promoter was performed to detect epigenetic alterations. Polymorphism analysis was used to determine loss of heterozygosity in tumour samples. Results: 95% of the expected mutations were identified in the tumour samples, with 16 samples exhibiting only one mutation, while two samples had no detectable RB1 mutation. 96% of bilateral/familial RB blood samples and 9.5% of unilateral sporadic blood samples, yielded mutations. 111 were novel mutations. Conclusions: The full range of screening techniques is required to achieve a high screening sensitivity in RB patients.

Background Eye salvage rate for group D retinoblastoma using intravenous chemotherapy (IVC) as a primary modality is <50%. To report on 13 years' experience with the use of primary IVC for group D retinoblastoma. Methods A retrospective analysis of 64 group D eyes (52 patients) treated with primary IVC, from 2002 to 2014. Results The median age at presentation was 11.0 months (mean: 18.6, range: 0.6–144.0), 35 (67%) patients had bilateral disease, 38 (73%) germline disease and 8 (15%) cases were familial. In addition to IVC, patients received a median number of three treatments (mean: 6, range: 0–24), including thermotherapy/cryotherapy, plaque radiotherapy, intra-ophthalmic artery chemotherapy (IAC) and/or intravitreous chemotherapy. External beam radiotherapy (EBRT) was used in five eyes, all of which were eventually enucleated. In a median follow-up time of 55 months (mean: 64, range: 14–156), 63% of eyes were salvaged. By the Kaplan-Meier survival analysis, globe salvage rate was 83%, 70%, 59% and 45% at 1, 3, 5 and 10 years, respectively. There were no cases of metastatic spread from intraocular retinoblastoma and no deaths. IVC-related adverse events included febrile neutropenia in 21 (40%) patients and anaphylactic reaction to carboplatin in 2 (4%), all conservatively resolved. Of the patients receiving IAC, third and sixth nerve palsies were documented in two (10%) and one (5%) eyes, respectively. Conclusions Primary IVC for group D eyes, with adjuvant treatments as required, was found to be a safe and efficient approach, achieving 63% eye salvage rate, no metastatic spread from intraocular retinoblastoma and no deaths. IAC has now replaced EBRT as a successful salvage treatment.

The development of retinoblastoma is thought to require pathological genetic changes in both alleles of the RB1 gene. However, cases exist where RB1 mutations are undetectable, suggesting alternative pathways to malignancy. We used whole-genome sequencing (WGS) and transcriptomics to investigate the landscape of sporadic retinoblastomas derived from twenty patients, sought RB1 and other driver mutations and investigated mutational signatures. At least one RB1 mutation was identified in all retinoblastomas, including new mutations in addition to those previously identified by clinical screening. Ten tumours carried structural rearrangements involving RB1 ranging from relatively simple to extremely complex rearrangement patterns, including a chromothripsis-like pattern in one tumour. Bilateral tumours obtained from one patient harboured conserved germline but divergent somatic RB1 mutations, indicating independent evolution. Mutational signature analysis showed predominance of signatures associated with cell division, an absence of ultraviolet-related DNA damage and a profound platinum-related mutational signature in a chemotherapy-exposed tumour. Most RB1 mutations are identifiable by clinical screening. However, the increased resolution and ability to detect otherwise elusive rearrangements by WGS have important repercussions on clinical management and advice on recurrence risks.