This test analyzes the RB1 gene for the hereditary form of retinoblastoma (Rb), which is a rare cancer that forms in the retina of the eye. Retinoblastoma typically develops in children under the age of 5. Most cases are sporadic, but approximately 40% are inherited. In addition to Rb, those with the hereditary form of this condition are also at increased risk to develop other non-ocular tumors, including pinealoma, osteosarcoma, soft tissue sarcomas, and melanoma.
Genetic testing of this gene may confirm a diagnosis and help guide treatment and management decisions. Identification of a disease-causing variant would also guide testing and diagnosis of at-risk relatives. This test is specifically designed for heritable germline mutations and is not appropriate for the detection of somatic mutations in tumor tissue.
Retinoblastoma (Rb) is a rare, early-childhood cancer that forms in the retina of the eye. Most cases are sporadic, unilateral, and diagnosed before the age of 5; however, 40% are bilateral and due to an inherited pathogenic variant in the RB1 gene. Those with hereditary Rb also have an increased risk of developing other cancers outside of the eye, including pinealoma, osteosarcoma, soft tissue sarcomas, and melanoma. These typically present in adolescence and adulthood.
Common early clinical signs of Rb are leukocoria (white pupillary reflex), strabismus, vision loss, persistent eye pain, redness, and irritation. Retinoblastoma is often curable when diagnosed early, but if it is left untreated, this cancer can metastasize and become life-threatening.
Patients with hereditary retinoblastoma carry a significant risk of secondary nonocular tumors. Radiation therapy administered before the age of 12 months is known to increase this risk.
|pinealoblastoma||up to 5.5% (PMID: 23876864)|
|soft tissue sarcomas, osteosarcoma, carcinoma, melanoma, leukemia||elevated (PMID: 22355046)|
Analysis of the RB1 gene identifies a pathogenic variant in more than 95% of individuals with hereditary retinoblastoma.
Rb is inherited in an autosomal dominant manner. A few cases are inherited, but most occur as the result of a spontaneous new mutation.
The prevalence of retinoblastoma is estimated at between 1 in 15,000 and 1 in 20,000 individuals.
Analysis of the RB1 gene may be considered for individuals with:
Invitae is a College of American Pathologists (CAP)-accredited and Clinical Laboratory Improvement Amendments (CLIA)-certified clinical diagnostic laboratory performing full-gene sequencing and deletion/duplication analysis using next-generation sequencing technology (NGS).
Our sequence analysis covers clinically important regions of each gene, including coding exons, +/- 10 base pairs of adjacent intronic sequence, and select noncoding variants. Our assay provides a Q30 quality-adjusted mean coverage depth of 350x (50x minimum, or supplemented with additional analysis). Variants classified as pathogenic or likely pathogenic are confirmed with orthogonal methods, except individual variants that have high quality scores and previously validated in at least ten unrelated samples.
Our analysis detects most intragenic deletions and duplications at single exon resolution. However, in rare situations, single-exon copy number events may not be analyzed due to inherent sequence properties or isolated reduction in data quality. If you are requesting the detection of a specific single-exon copy number variation, please contact Client Services before placing your order.
|Gene||Transcript reference||Sequencing analysis||Deletion/Duplication analysis|