Treatment of Retinoblastoma: The Role of External Beam Radiotherapy

The risk of radiotherapy-related secondary cancers in children with constitutional retinoblastoma 1 (RB1) mutations has led to reduced use of external beam radiotherapy (EBRT) for RB. Presently, tumor reduction with chemotherapy with or without focal surgery (chemosurgery) is most commonly undertaken; EBRT is avoided as much as possible and is considered only as the last treatment option prior to enucleation. Nevertheless, approximately 80% of patients are diagnosed at a locally advanced stage, and only 20-25% of early stage RB patients can be cured with a chemosurgery strategy. As a whole, chemotherapy fails in more than two-thirds of eyes with advanced stage disease, requiring EBRT or enucleation. Radiotherapy is still considered necessary for patients with large tumor(s) who are not candidates for chemosurgery but who have visual potential. When radiation therapy is indicated, the lowest possible radiation dose combined with systemic or local chemotherapy and focal surgery may yield the best clinical outcomes in terms of local control and treatment-related toxicity. Proton beam therapy is one EBRT method that can be used for treatment of RB and reduces the radiation dose delivered to the adjacent orbital bone while maintaining an adequate dose to the tumor. To maximize the therapeutic success of treatment of advanced RB, the possibility of integrating radiotherapy at early stages of treatment may need to be discussed by a multidisciplinary team, rather than considering EBRT as only a last treatment option.

Identification of three new mutations in the RB1 gene in patients with sporadic retinoblastoma in Colombia / Identificación de tres nuevas mutaciones en el gen RB1 en pacientes con retinoblastoma esporádico en Colombia

Introduction. Retinoblastoma is a childhood cancer of the retina originated by altered or null retinoblastoma protein (pRb) expression. Genetic alterations in both RB1 alleles in the retinal cells are required for the development of retinoblastoma. In the sporadic form, non-hereditary RB1 gene mutations take place in a single retinoblast cell, and are therefore only present in tumor DNA (somatic mutations). Sporadic retinoblastoma is primarily unilateral, lacks family history and has no risk of transmission to descendants. Genetic tests for detection of RB1 mutation has improved the identification of carriers and facilitated accurate genetic counseling. Objective. To identify mutations in the RB1 gene in Colombian patients with sporadic retinoblastoma by PCR-SSCP followed by sequence. Materials and methods. Four patients with sporadic retinoblastoma were analyzed by PCR-SSCP, followed by DNA sequencing to identify variations in the RB1 gene. Results. We identified five variations in RB1 gene: three new mutations (one germline and two somatic mutations), one new polymorphism and one already reported somatic mutation. Four mutations were found in three patients with unilateral retinoblastoma and one mutation was found in a patient with bilateral retinoblastoma. One of these was a germline mutation in a sporadic unilateral retinoblastoma that was not present in the parents or three siblings analyzed. Conclusions. Our results emphasize the importance of identifying mutations for genetic counseling and clinical management of sporadic retinoblastoma patients. Description of a new RB1 gene variant is interesting since there have been a small number of polymorphisms reported for this gene.

Introducción. El retinoblastoma es un cáncer pediátrico de la retina originado por la expresión alterada o ausente de la proteína del retinoblastoma (pRb). Se requiere la alteración genética de ambos alelos RB1 en las células de la retina para el desarrollo del retinoblastoma. En la forma esporádica, las mutaciones no hereditarias del gen RB1 ocurren en un solo retinoblasto y están presentes sólo en el ADN del tumor (mutaciones somáticas). El retinoblastoma esporádico es generalmente unilateral, no tiene historia familiar y no tiene riesgo de transmisión a la descendencia. Las pruebas genéticas para la detección de mutaciones en RB1 han mejorado la identificación de portadores y han facilitado la precisión de la asesoría genética. Objetivo. Detectar mutaciones en el gen RB1 en pacientes colombianos con retinoblastoma esporádico mediante PCR-SSCP seguido de secuenciación. Materiales y métodos. Se analizaron cuatro pacientes con retinoblastoma esporádico para la detección de variaciones en el gen RB1 mediante PCR-SSCP, seguida de secuenciación. Resultados. Se identificaron cinco variaciones del gen RB1 : tres mutaciones nuevas (una de línea germinal y dos somáticas), un polimorfismo nuevo y una mutación somática ya reportada. Las cuatro mutaciones se encontraron en tres pacientes con retinoblastoma unilateral y uno con bilateral. La mutación germinal se detectó en un paciente con compromiso unilateral y no se encontró en los padres ni en los tres hermanos analizados. Conclusión. Estos resultados enfatizan la importancia, para asesoría genética y manejo clínico, de identificar mutaciones del gen RB1 en pacientes con retinoblastoma esporádico. La descripción de una nueva variante en RB1 es interesante, dado el muy bajo número de polimorfismos reportados para este gen.

Perspectivas en la genómica del retinoblastoma: Implicaciones del gen supresor de tumor RB1 / Genomic retinoblastoma perspectives: Implications of supressor gene of tumor RB1

In order to define the molecular and cellular bases of the development of retinoblastomas it is necessary to know its etiology, and to apply the advances in genome technology to this kind of neoplasia. Retinoblastomas are childhood tumors of the eye with an average incidence of one case in every 15,000-20,000 live births, which occur in sporadic and hereditary forms. The sporadic form appears regularly as a unilateral tumor, while in the familial form of the disease, tumors may be unilateral and bilateral. This neoplasia is characterized by leukocoria, strabism, and heterochromia. The retinoblastoma gene (RBl) is a molecular marker of retinoblastoma tumors. This gene is located in chromosome 13q14.2 and encodes a nuclear phosphoprotein (pRB) of 110 KDa, which plays a major role in cell proliferation control through cell cycle-regulated phosphorylation/dephosphorylation cycles of this protein. The RBl gene is mainly affected by point mutations, which occur most frequently in exons 3, 8, 18 and 20. At the end of the last century, DNA technology has improved notably, allowing for its application to the study of a vast array of diseases. The aim of this work is to show the molecular aspects involved in retinoblastoma which are currently deciphering; this is possible thanks to new technology platforms that have been developed. This will allow us in a near future, to offer tests for the early diagnoses, prognoses, and the determination of individual predisposition towards this neoplasia.

El retinoblastoma es una neoplasia embrionaria que se manifiesta en dos formas: esporádica (no heredada) o familiar (heredada). En los casos esporádicos el tumor es unilateral y en la forma familiar puede presentarse de manera unilateral o bilateral. Esta neoplasia tiene una incidencia promedio de 1/15,000 nacidos vivos, presentando signos y síntomas que incluyen leucocoria, estrabismo, midriasis unilateral y heterocromía. El gen que predispone al desarrollo de retinoblastoma es RBl y se localiza en el cromosoma 13 en la región ql4.2. El gen RBl codifica para una fosfoproteína nuclear que participa de manera importante en la regulación del ciclo celular. De acuerdo con la hipótesis de Knudson, para que se desarrolle la neoplasia se deben presentar dos mutaciones en el gen RBl. Las mutaciones puntuales son las que más frecuentemente se presentan en el gen RBl; la mayoría de los estudios indican que los exones 3, 8, 18, 19 y 20 son las regiones de mutación preferencial. En la áltima década ha habido un gran avance en la tecnología del DNA, lo cual hace posible su aplicación en diferentes enfermedades. Estas herramientas moleculares podrían ser de gran utilidad en el diagnóstico o conocimiento de la predisposición a desarrollar un retinoblastoma. Entre estas valiosas herramientas se cuenta con la hibridación fluorescente realizada in situ, hibridación genómica comparativa, las microhileras y por áltimo la identificación de polimorfismos de un sólo nucleótido. En conclusión, actualmente se están descifrando los aspectos moleculares que están relacionados con el retinoblastoma, gracias a la aplicación de nuevas plataformas tecnológicas. Esto permitirá en un futuro próximo ofrecer pruebas para un diagnóstico temprano o para conocer el pronóstico y la predisposición de individuos a desarrollar esta patología. Con el fin de entender las bases celulares y moleculares del desarrollo del retinoblastoma, el objetivo del presente trabajo es mostrar el estado del arte del conocimiento de esta neoplasia, así como su origen y los avances en la genómica aplicada al retinoblastoma.

Retinoblastoma familial associado a carcinoma primário de plexo coróide. Relato de caso / Familial retinoblastoma associated to primary choroid plexus carcinoma. Report of a case

Retinoblastoma éum tumor originado de células neuropiteliais da retina, que pode ocorrer de forma esporádica ou familial e está relacionado com o gene RB-1, do braço longo do cromossomo 13 (regiäo 13q14). Este gene é um supressor tumoral e quando sofre deleçäo promove crescimento celular. O retinoblastoma relaciona-se com a mutaçäo dos dois alelos RB-1: quando o indivíduo sofre duas mutaçöes durante o desenvolvimento somático da retina, ele tem a forma esporádica ou näo hereditária da doença; quando uma das mutaçöes é herdada de células germinativas, ele tem a familial ou hereditária. Apresentamos um caso de retinoblastoma bilateral, familial, associado com carcinoma primário de plexo coróide. Após revisäo, näo encontramos associaçäo semelhante na literatura.

Associaçäo do retinoblastoma ao osteossarcoma: relato de dois casos / Retinoblastoma associated with osteosarcoma: report of two cases

O retinoblastoma é o tumor ocular mais freqüente na infância, geralmente diagnosticado nos primeiros três anos de vida, podendo ser uni ou bilateral. Acredita-se que seja de etiologia gênica e atualmente, com o aumento na sobrevida destes pacientes, tem-se observado outros tumores primários associados, mais freqëntemente o osteossarcoma osteoblástico. Os autores relatam dois casos de osteossarcoma osteoblástico em crianças que foram submetidas anteriormente a enucleaçäo de olho bilateral e unilateral, respectivamente, por retinoblastoma, O objetivo deste trabalho é apresentar dois novos casos na literatura médica e descrever consideraçöes sobre a correlaçäo entre as duas entidades.

PCR detection of Xbal polymorphism in the human Rb gene of retinoblastoma patients

Inactivation of the Rb (retinoblastoma) tumor suppressor gene is associated with hereditary and sporadic cases of retinoblastoma and other Rb-related tumors. Early diagnosis and genetic counseling heavily depend on practical methods for the detection of Rb deletions and mutations in high-risk families. Here we report on the use of a pair of primers in polymerase chain reaction (PCR) to amplify a 945-bp fragment from intron 17 of the Rb gene (T.L. McGee, G.S. Cowley, D.W. Yandell and T.P. Dryja, 1990, Nucleic Acid Research, 18: 207). Xbal digestion of the PCR product reveals 2 allelic versions: a single 945-bp fragment (allele 1) or 2 fragments of 315 and 630 bp (allele 2). We used total genomic DNA (blood and tumors) to investigate the power of this PCR-Rb-Xbal-RFLP in the identification of both segregation and loss of heterozygosity of the Rb gene. In one family studied (family 1A) in which 2 generations were affected, it was possible to localize the mutated Rb gene to Xbal-Rb allele 2. The assay of loss of heterozygosity of the Rb gene is available for all Xbal-Rb allele 1-2 individuals, so that analyses may be applied in large scale investigation of the participation of Rb gene in tumor development. We conclude that PCR-Rb-Xbal-RFLP is a practical and powerful tool for oncology research and genetic counseling

Loss of retinoblastoma gene and amplification of N-myc gene in retinoblastoma

We have analyzed paired samples of genomic DNA from peripheral leukocyte and primary tumor tissue from nine patients with retinoblastoma (RB) and from two RB cell lines, WERI-Rb-1 and Y79, to detect the molecular alterations of the retinoblastoma susceptibility gene (RB-1) and N-myc gene. In Southern analysis, RB-1 deletions in tumor tissues were detected in five patients (56%), one of these revealed a total loss of RB-1. N-myc amplification was found only in one (11.1%) out of nine patients. We also observed a total loss of RB-1 in WERI-Rb-1, and a more than 100-fold amplification of N-myc in Y79. The analysis of the relationship between molecular events and clinical characteristics such as age, sex, tumor laterality did not reveal any specific correlation. These results suggest that genetic backgrounds of RB in Korean patients are quite similar to those of reported cases elsewhere. The high sensitivity of our method in detecting the RB-1 loss indicates that this method can be a useful tool for initially screening a large number of tumors.

Análisis de la herencia del retinoblastoma en 8 familias / Analysis of inheritance of retinoblastoma in eight families

Se presentan los árboles genealógicos de 8 propositi afectados por retinoblastoma (Rb): 7 bilaterales (RbB) y uno unilateral (RbU). Se señala que las variaciones intrafamiliares se analizaron teniendo en cuenta que la penetrancia del gen Rb que se ha estimado es del 80 %, el modelo mutacional multietapa propuesto por knudson y la hipótesis resistencia-hospedero de Matsunaga

Retinoblastoma familiar predispondo ao surgimento de um segundo tumor primário näo ocular / Hereditary retinoblastoma associated with a second non-ocular primary tumor

Os autores relatam um caso de retinoblastoma familiar associado ao aparecimento de um segundo tumor primário näo ocular e discutem possíveis teorias genéticas que predisporiam a estas duas neoplasias

Origen y genética del retinoblastoma / Origin and genetics of retinoblastoma

Se estudiaron 51 pacientes afectados de retinoblastoma, de los cuales 30 estaban comprometidos en forma unilateral y los 21 restantes en forma bilateral. De ellos se seleccionaron 5 pedigrees completos de casos hereditarios los que nos sirvieron de base para explicar las dos principales teorías de transmisión genética para esta enfermedad: 1) de Auerbach o Mutación Demorada 2) de Kundson o Multietapas Mutacionales. Completamos con asesoramiento y consejo genético

Perfil ecográfico, histológico e genético dos retinoblastomas / Echographic, histologic and genetic profile of retinoblastomas

É feito um estudo estatístico relativo à freqüência do retinoblasma nos Serviços de Oftalmologia dependentes da Faculdade de Medicina de Lisboa, e muito especialmente no Instituto de Oftalmologia Dr. Gama Pinto. Analisa-se o perfil ecográfico do retinoblastoma em momentos diferentes do seu desenvolvimento e em tipos clínicos distintos. Dá-se relevo especial nas formas unilaterais, de resto as mais freqüentes, ao estudo clínico e ecográfico do olho adelfo. A variedade dos perfis ecográficos contribui para que seja definida uma classificaçäo clínica dos retinoblastomas. Consideram-se as suas características histológicas e faz-se a sua comparaçäo com os perfis ecográficos obtidos. Faz-se para o retinoblastoma, o adequado estudo genético analisando-se as formas seguramente hereditárias e as formas esporádicas. Avalia-se o cariotipo dos doentes e reconhece-se a possibilidade do cariotipo revelador

Angiotomatose retiniana afetando irmäo e irmä

Os autores fazem uma revisäo das Facomatoses, com especial enfoque para a Doença de Von Hippel-Lindau. Dois casos (irmäo e irmä) säo apresentados