Lack of correlation between age at diagnosis and RB1 mutations for unilateral retinoblastoma: the importance of genetic testing

Conditional analysis on new tumor formation with solitary unilateral retinoblastoma in 482 consecutive patients

PURPOSE

The objective of the study was to understand dynamic risk (conditional analysis based on patient age) for new tumor development in patients with solitary unilateral retinoblastoma.

METHODS

This was a retrospective analysis.

RESULTS

Of 482 patients with solitary unilateral retinoblastoma, 55 new tumors developed in 20 patients (4%). Comparison (new tumor vs. no new tumor development) revealed those with new tumor demonstrated younger mean age at presentation (10 vs. 36 months, P < 0.001), greater likelihood of family history of retinoblastoma (35% vs. 3%, P < 0.001), and greater probability of primary tumor location in the macula (50% vs. 15%, P = 0.003). Conditional risk for new tumors (at age 6, 9, 12, 18, and 24 months) declined for those who presented at 0-3 months old (25%, 15%, 15%, 8%, and 0%), >3-6 months old (17%, 14%, 6%, 6%, and 0%), >6-9 months old (not applicable [na], 6%, 6%, 0%, and 0%), and >9-12 months (na, na, 3%, 3%, and 0%). Younger patients showed greater development of bilateral tumors (P < 0.001). Of patients with new tumors, those that occurred within 1 year from presentation were located in the preequatorial region in 46%, whereas those that occurred more than 1 year from presentation were preequatorial in 78%. Patients ≤24 months at initial presentation demonstrated all new tumors by 24 months of age. Older patients (>24 months at presentation) showed new tumors up to 56 months of age.

CONCLUSION

Children (≤24 months) with solitary unilateral retinoblastoma showed decreasing risk for new tumors up to 24 months of life. Later onset of new tumor was more likely located in preequatorial region.

Retinoblastoma: emerging concepts in genetics, global disease burden, chemotherapy outcomes, and psychological impact

In this review we discuss several recent concepts regarding retinoblastoma control and its impact. In a cohort of 482 patients with solitary unilateral retinoblastoma revealed germline mutation in 16% and the likelihood of germline retinoblastoma was greater for younger children (≤1 year versus (vs.) >1 year at presentation) with odds ratio (OR) 2.96 (p = 0.001), and greatest for the youngest infants (≤3 months vs. >3-12 months) (OR 5.52) (p = 0.002). Retinocytoma/retinoma, a benign variant of retinoblastoma, was studied in 78 tumours and demonstrated transformation into retinoblastoma in 9.2% by 5 years and 15.3% by 10 years and 20 years. An international global study on retinoblastoma over 1.5 years revealed 4351 new patients and 85% from low- and middle-income countries, notably with older age at detection and greater risk for metastasis. Management of retinoblastoma in 964 eyes using intravenous chemotherapy showed 20-year globe salvage at 96% in group A, 90% in group B, 90% in group C, 68% in group D, and 32% in group E eyes. The 5-year globe salvage with intra-arterial chemotherapy for 160 eyes (655 infusions) with retinoblastoma showed success in 100% for group B, 80% for group C, 78% for group D, and 55% for group E. The psychological impact of retinoblastoma on the parents revealed depression (73%), anxiety (64%), and/or stress (100%), and on the patient revealed deficits in quality of life issues. Retinoblastoma is a challenging disease and chemotherapy provides reliable tumour control and globe salvage. Continuing efforts to improve quality of life issues is important.

Likelihood of Germline Mutation With Solitary Unilateral Retinoblastoma Based on Patient Age at Presentation: Analysis of 482 Consecutive Patients

PURPOSE

To evaluate the likelihood of germline retinoblastoma in patients presenting with solitary unilateral retinoblastoma, based on age at presentation.

METHODS

This retrospective case series of 482 consecutive patients presenting with solitary unilateral retinoblastoma analyzed the likelihood of germline retinoblastoma, defined as family history of retinoblastoma, germline retinoblastoma mutation documented on genetic testing, and/or development of bilateral disease and/or additional new tumors. This analysis was based on age at presentation (0 to 12 months vs older than 12 to 24 months vs older than 24 to 36 months vs older than 36 months) and a sub-study was conducted on infant age at presentation (0 to 3 months vs older than 3 to 6 months vs older than 6 to 9 months vs older than 9 to 12 months).

RESULTS

Of the overall group (482 consecutive patients) with solitary unilateral retinoblastoma, there were significantly different findings in the youngest age group (0 to 12 months old) with greater family history of retinoblastoma (10% vs 2% vs 1% vs 2%, P = .004), smaller median basal diameter (18.0 vs 20.0 vs 20.0 vs 20.0 mm, P = .014), smaller median tumor thickness (8.7 vs 10.0 vs 11.5 vs 10.0 mm, P = .002), greater macular tumor location (33% vs 16% vs 10% vs 8%, P < .001), and greatest likelihood of germline mutation (29% vs 17% vs 8% vs 9%, P = .001). By comparison, patients 1 year and younger (vs older than 1 year) demonstrated a 2.96 odds ratio (OR) (P = .001) for likelihood of germline retinoblastoma. For those classified as infants (1 year and younger) (n = 132 consecutive patients), the youngest patients (0 to 3 months old) demonstrated the greatest likelihood for germline mutation (61% vs 20% vs 24% vs 22%, P = .009) and greatest odds ratio (5.52, P = .002) compared to patients older than 3 to 12 months.

CONCLUSIONS

The youngest patients with solitary unilateral retinoblastoma showed the greatest likelihood of germline disease when evaluating all patients (1 year and younger vs older than 1 year of age) (OR = 2.96) and the substudy of infants (3 years and younger vs older than 3 to 12 months old) (OR = 5.52). [J Pediatr Ophthalmol Strabismus. 2021;58(6):355-364.].

Clinical evaluation of RB1 genetic testing reveals novel mutations in Vietnamese patients with retinoblastoma

Clinical evaluation of the genetic testing strategy is essential for ensuring the correct determination of mutation carriers. The current study retrospectively analyzed genetic and clinicopathological data from 62 Vietnamese patients with retinoblastoma (RB) referred to the Vinmec Hi-Tech Center for RB transcriptional corepressor 1 (RB1) genetic testing between 2017 and 2019. The present study aimed to evaluate the sensitivity of the Next Generation Sequencing (NGS) method to identify novel RB1 mutations, and to consider using age at diagnosis as a risk factor. Genomic DNA was analyzed with custom panel based targeted NGS. NGS was performed on the Beijing Genomics Institute (BGI) sequencing platform, and pathogenic or likely pathogenic variants were confirmed by Sanger sequencing, quantitative PCR (qPCR) or Multiplex Ligation-dependent Probe Amplification assay (MLPA). Constitutional RB1 variants were identified in 100% (25/25) of the bilateral cases, while several common previously reported RB1 mutations were also recorded. In addition, in Vietnamese patients with RB, nine novel RB1 mutations were identified. Children aged between 0-36 months were more likely to be RB1 carriers compared with those aged >36 months. The current findings indicated that the NGS method implemented in the Vinmec Hi-Tech Center was highly accurate, and age at diagnosis may be used to assess the risk of hereditary RB. Furthermore, the newly identified RB1 mutations may provide additional data to improve the current understanding of the mechanisms underlying RB1 inactivation and the development of rapid assays for detecting RB1 mutations. Overall, the present study suggested that NGS may be applied for detecting germline RB1 mutations in routine clinical practice.

Simultaneous identification of clinically relevant RB1 mutations and copy number alterations in aqueous humor of retinoblastoma eyes

BACKGROUND

Detection of germline RB1 mutations is critical for risk assessment of retinoblastoma (RB) patients. Assessment of somatic copy number alterations (SCNAs) is also critically important because of their prognostic significance. Herein we present a refined approach for the simultaneous identification of RB1 variants and SCNAs in the aqueous humor (AH) of RB eyes.

MATERIALS AND METHODS

Subjects included 7 eyes of 6 RB patients that underwent AH extraction, and 4 matched tumor samples. Cell-free DNA (cfDNA) was isolated and sequenced to assess genome-wide SCNAs. The same sequencing libraries then underwent targeted resequencing and mutation detection using a custom hybridization panel that targets RB1 and MYCN. Illumina paired-end 2x150bp sequencing was used to characterize single-nucleotide variants (SNVs) and loss of heterozygosity (LOH). Results were compared to peripheral blood RB1 testing. Tumor fraction (TFx) was calculated using ichorCNA.

RESULTS

Four of 7 AH samples contained clinically significant SCNAs. Of the 3 other samples, 1 showed focal MYCN amplification and 1 showed focal RB1 deletion. All 4 enucleated tumors contained SCNAs. Mutational analysis of tumor DNA identified all first hits (2 germline RB1 SNVs, 2 germline CNAs) and second hits (4 RB1 SNVs). RB1 variants in AH were concordant with those obtained from corresponding tumor tissue and blood. In AH samples without paired tumor, both RB1 hits were identified with high variant allele frequency, even in the absence of SCNAs.

CONCLUSIONS

AH liquid biopsy is a minimally invasive, in vivo alternative to tissue analysis for the simultaneous identification of RB1 variants and SCNAs in RB eyes.

Variability in retinoblastoma genome stability is driven by age and not heritability

Retinoblastoma (RB) is a childhood intraocular cancer initiated by biallelic inactivation of the RB tumor suppressor gene (RB1^-/- ). RB can be hereditary (germline RB1 pathogenic allele is present) or non-hereditary. Somatic copy number alterations (SCNAs) contribute to subsequent tumorigenesis. Previous studies of only enucleated RB eyes have reported associations between heritability status and the prevalence of SCNAs. Herein, we use an aqueous humor (AH) liquid biopsy to investigate RB genomic profiles in the context of germline RB1 status, age, and International Intraocular Retinoblastoma Classification (IIRC) clinical grouping for both enucleated and salvaged eyes. Between 2014 and 2019, AH was sampled from a total of 54 eyes of 50 patients. Germline RB1 status was determined from clinical blood testing, and cell-free DNA from AH was analyzed for SCNAs. Of the 50 patients, 23 (46.0%; 27 eyes) had hereditary RB, and 27 (54.0%, 27 eyes) had non-hereditary RB. Median age at diagnosis was comparable between hereditary (13 ± 10 months) and non-hereditary (13 ± 8 months) eyes (P = 0.818). There was no significant difference in the prevalence or number of SCNAs based on (1) hereditary status (P > 0.56) or (2) IIRC grouping (P > 0.47). There was, however, a significant correlation between patient age at diagnosis, and (1) number of total SCNAs (r[52] = 0.672, P < 0.00001) and (2) number of highly-recurrent RB SCNAs (r[52] = 0.616, P < 0.00001). This evidence does not support the theory that specific molecular or genomic subtypes exist between hereditary and non-hereditary RB; rather, the prevalence of genomic alterations in RB eyes is strongly related to patient age at diagnosis.

Next-Generation Technologies and Strategies for the Management of Retinoblastoma

Retinoblastoma (RB) is an inherited retinal disorder (IRD) caused by the mutation in the RB1 gene or, rarely, by alterations in the MYCN gene. In recent years, new treatment advances have increased ocular and visual preservation in the developed world. The management of RB has improved significantly in recent decades, from the use of external beam radiation to recently, more localized treatments. Determining the underlying genetic cause of RB is critical for timely management decisions. The advent of next-generation sequencing technologies have assisted in understanding the molecular pathology of RB. Liquid biopsy of the aqueous humor has also had significant potential implications for tumor management. Currently, patients’ genotypic information, along with RB phenotypic presentation, are considered carefully when making treatment decisions aimed at globe preservation. Advances in molecular testing that improve our understanding of the molecular pathology of RB, together with multiple directed treatment options, are critical for developing precision medicine strategies to treat this disease.

The RB1 Story: Characterization and Cloning of the First Tumor Suppressor Gene

The RB1 gene is the first described human tumor suppressor gene and plays an integral role in the development of retinoblastoma, a pediatric malignancy of the eye. Since its discovery, the stepwise characterization and cloning of RB1 have laid the foundation for numerous advances in the understanding of tumor suppressor genes, retinoblastoma tumorigenesis, and inheritance. Knowledge of RB1 led to a paradigm shift in the field of cancer genetics, including widespread acceptance of the concept of tumor suppressor genes, and has provided crucial diagnostic and prognostic information through genetic testing for patients affected by retinoblastoma. This article reviews the long history of RB1 gene research, characterization, and cloning, and also discusses recent advances in retinoblastoma genetics that have grown out of this foundational work.