Retinoblastoma epidemiology and demographics
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
There is no predisposition for retinoblastoma by race or gender. Right and left eyes are affected equally. It is the most common intraocular tumor of the childhood. The incidence of retinoblastoma worldwide ranges from 1 in 14,000 live births to 1 in 34,000.[1] The mean age-adjusted incidence rate of retinoblastoma is 11.8 cases per million children aged 0-4 years in the USA and it is similar to rates reported from European countries and the age-adjusted incidence rate of retinoblastoma in the USA as well as bilateral cases (26.7%) versus unilateral cases (71.9%) remained stable from 1975-2004.[2] In a study which was done on 206 children with retinoblastoma, the mean age at diagnosis was 21.2 mo in the total study group and the mean age at diagnosis in the bilateral cases (14.6 months) was substantially less than in the unilateral ones (23.5 months) and the great majority of patients (approximately 75%) had advanced disease (group V in both Reese-Ellsworth and Essen prognosis classifications) in the affected eye (unilateral cases) or the more severely affected eye (bilateral cases).
SEER highlights
Here are some highlights listed by the SEER(Surveillance, Epidemiology and End Results) about the incidence of retinoblastoma among children and adolescents.[3]
- Retinoblastoma accounted for approximately 11% of cancers developing in the first year of life,but for only 3% of the cancers developing among children younger than 15 years of age.
- In the US, approximately 300 children and adolescents younger than 20 years of age are diagnosed with retinoblastomas each year.
- The vast majority of cases of retinoblastoma occur among young children with almost two-thirds(63%) of retinoblastomas occuring before the age of two years and 95% occuring before the age of 5 years.
- The incidence of bilateral tumors was strongly age dependent with 42% of the retinoblastomas occuring in children less than one year of age being bilateral compared to 21% of those among children aged one year, and only 9% among older children.
- Rates of retinoblastoma were the same among males(3.7 per million) and females(4.0 per million) and also among whites(3.7 per million) and blacks(4.0 per million).
- There was no subsantial change in the retinoblastoma incidence during the 21 year period, 1975-95.
Laterality, Unifocal versus Multifocal and Sporadic(Non Hereditary) versus Familial retinoblastoma
Bilateral Disease is always heritable. Unilateral, unifocal disease is not heritable. Most of the times, multifocal, unilateral disease is heritable and should prompt investigation for a germline mutation. To understand why it is so, the genetics of retinoblastoma needs to be discussed briefly. The RB1 gene is located on the human chromosome 13. to be precise it is on 13q14(long arm of 13th human chromosome). In familial retinoblastoma, the fertilized egg carries one defective copy of the RB1 gene, and all retinal cells in this offspring carry only a single functional RB1 gene copy. If this surviving copy is eliminated in a retinal cell by a somatic mutation (the second hit of the Knudson two-hit hypothesis), the cell will lack RB1 gene function and will proliferate into a tumor. In sporadic retinoblastoma, the fertilized egg is genetically wild type at the RB1 locus. In the retina of this offspring, retinoblastoma development requires two successive somatic mutations striking both copies of the RB1 gene in the retinal precursor cells. Because only a single somatic mutation is needed to eliminate RB1 function in familial cases, multiple cells in both eyes are affected. In contrast, the two somatic mutations required in sporadic disease are unlikely to affect a single cell lineage, yielding at most one tumor. Therefore familial retinoblastoma usually result in multifocal, bilateral disease and sporadic cases usually result in unifocal, unilateral tumor.
References
- ↑ Bishop JO, Madson EC (1975). "Retinoblastoma. Review of the current status". Survey of Ophthalmology. 19 (6): 342–66. PMID 1145423.
|access-date=requires|url=(help) - ↑ Broaddus E, Topham A, Singh AD (2009). "Incidence of retinoblastoma in the USA: 1975-2004". The British Journal of Ophthalmology. 93 (1): 21–3. doi:10.1136/bjo.2008.138750. PMID 18621794. Retrieved 2012-05-02. Unknown parameter
|month=ignored (help) - ↑ http://seer.cancer.gov/publications/childhood/retinoblastoma.pdf