Diagnosis and Current Management of Retinoblastoma

A Balmer, L Zografos and F Munier

Ocular Oncology Service, Jules Gonin University Eye Hospital, Lausanne, Switzerland

Retinoblastoma represents the prototypic model for 1999).Predisposition to malignant transformation may inherited cancers. The RB1 gene was the first tumor lead to a primary intracranial neuroblastic tumor, in suppressor gene to be identified. It represents the most particular pinealoblastoma (‘trilateral’ retinoblastoma) frequent primary eye cancer in children under 15 years (Kivela, 1999). old, habitually occurring in infancy, even in utero, but can Early treatment of the disease is straightforward, well be observed in older children or young adults. Many other tolerated, effective and at little cost, saving both life and retinal lesions may also simulate retinoblastoma. The two vision.Undertaken at a late stage, however, treatment is major presenting signs are leukocoria and strabismus, but heavy, mutilating and costly, with no certain outcome. other ocular or general signs may be observed. A highly This emphasizes the need for early diagnosis and the malignant tumor, retinoblastoma can nowadays be cured. importance of awareness at all levels, both public and The heritable form, however, carries a high risk of second professional (Balmer and Munier, 2002c). nonocular tumors. Treatment in the early stages of disease holds a good prognosis for survival and salvage of visual function. In very late stages, however, the prognosis for Epidemiology ocular function and even survival is jeopardized. Oncogene (2006) 25, 5341–5349. doi:10.1038/sj.onc.1209622 Retinoblastoma is a malignant tumor of the immature retina, the result of a double (‘two-hit’) oncogenic Keywords: retinoblastoma; tumor suppressor gene; mutation occurring between the start of the third month diagnosis; management postconception and the age of 4 years, this period representing the window of apparition and final maturity of retinoblasts.The cell of origin is most probably either a precursor cone photoreceptor cell or a multipotent retinoblast (Munier and Balmer, 2002).The Introduction disease may thus occur in utero and up to the age of 4 years, the average age at appearance of first signs being Retinoblastoma represents the prototypic model for 7 months for bilateral cases and 24 months for unilateral inherited cancers (Gallie and Phillips, 1984; Conway cases (Balmer and Munier, 2002a). et al., 2005). The Rb1 was the first tumor-suppressor Retinoblastoma may be nonheritable (60%) or gene to be identified, leading to the discovery of a whole heritable (40%), the latter by autosomal-dominant new class of antioncogenes and greatly contributing to transmission with high penetrance (90%). advances in the management of solid tumors in children. The incidence of retinoblastoma is given in the Although a rare disease, retinoblastoma is the most literature as 1 in 20 000 live births (Balmer and Munier, frequent primary eye cancer in children under 15 years 2002b) with no gender or race predilection and no old (Mahoney et al., 1990). It may also be simulated by significant environmental or socio-economic factors. other lesions.Retinoblastoma is almost exclusively a The age of the parents, paternal in particular, may play disease of childhood, has even been detected in the a role according to some authors (DerKinderen et al., foetus (Maat-Kievit et al., 1993) but can also occur in 1990; Matsunaga et al., 1990). Although rare, retino- older children and, in exceptional cases, young adults blastoma represents 80% of all primary ocular cancers (Shields et al., 1991). Diagnosis is often late, in spite of in children up to 15 years old, 1% of all cancer-related clear warning signs (Balmer and Munier, 2002a). deaths (Miller, 1969) and rates third highest of all A malignant tumor now considered curable, some intraocular tumors in all ages (Scat et al., 1996). cases of retinoblastoma show ‘spontaneous’ regression. With the heritable form, however, there remains a major risk of second nonocular primary tumors, these even Presentation more lethal than the retinoblastoma itself (Abramson, Leukocoria is the most common presenting sign in Correspondence: Dr A Balmer, Hoˆ pital Ophtalmique Jules Gonin, patients with retinoblastoma (60%) (Figure 1) but is Avenue de France 15, 1004 Lausanne, Switzerland. a late sign, the survival rate high (88% at 5 years) E-mail: [email protected] but poor for globe salvage (Beaverson et al., 2001). Diagnosis and current management of retinoblastoma A Balmer et al 5342

Figure 1 Leukocoria, most common warning sign of retinoblastoma.

The second major presenting sign is strabismus (20%), this usually the result of macular involvement and an early sign, the survival rate high and with a good chance of globe salvage (Beaverson et al., 2001). The remaining 20% present atypical signs, often inﬂam- matory these usually late signs with a much poorer Figure 2 Endophytic tumor growth pattern, group B retinoblastoma survival and globe salvage prognosis (Binder, 1974; (ABC Classiﬁcation). Balmer et al., 1993).

Clinical ﬁndings

The clinical presentation of retinoblastoma depends on the tumor growth pattern, duration, degree of vascularization and the presence of calcifications, vitreous seeding, retinal detachment or hemorrhage.Tumors may show an endophytic growth pattern (Figure 2), resulting from cell division within the internal retinal layers and tumor growth towards the vitreous.An exophytic growth pattern (Figure 3) is initiated in the external retinal layers, the tumor developing beneath the retina in the subretinal space and causing an overlying retinal detachment.A mixed growth represents the association of both endophytic and exophytic patterns. Exceptionally (2%), in its diffuse infiltrating (plaque- like) form, retinoblastoma may develop in a flat pattern on the surface of, or beneath, the retina, with no obvious Figure 3 Exophytic tumor growth pattern, group D retinoblastoma mass and no calcifications, progressing slowly towards (ABC Classification). the anterior segment where late signs present in the form of pseudoinflammatory complications. Endophytic retinoblastoma presents as one or several tumors, isolated or coalesced, of variable size, round or oval-shaped, yellowish-white in color (calcifications) or pink (vascularization), with a regular or sometimes turgescent and tortuous vascular network.Tumor localization is statistically age-dependent, the earliest tumors developing in the posterior pole, more peripheral tumors developing later (Abramson and Gombos, 1996).Endophytic tumors show a marked tendency to vitreous seeding (Figure 4). Exophytic retinoblastoma presents with retinal detachment, this masking to a greater or lesser degree the underlying tumor masses. Diffuse infiltrating retinoblastoma, sometimes visible as an irregular greyish plaque on the retinal surface, usually presents with a pseudohypopyon (Girard et al., 1989; Morgan, 1971). Finally, retinoma or retinocytoma is a benign form of Figure 4 Endophytic growth pattern with extensive vitreous retinoblastoma, characterized by greyish, homogenous, seeding, group D retinoblastoma (ABC Classification).

Oncogene Diagnosis and current management of retinoblastoma A Balmer et al 5343 more or less translucent masses, with calciﬁcations proximity to the macula and the optic nerve, the degree and border pigmentation imitating an irradiated retino- of seeding and importance of retinal detachment and, blastoma (Gallie et al., 1982; Margo et al., 1983; Balmer ﬁnally, late complications (Figures 2–7). et al., 1991; Singh et al., 2000). Importantly, this benign form of retinoblastoma is nevertheless susceptible to malignant transformation at a later stage. Dissemination pathways

Classification The poorly cohesive high-index mitotic retinoblastoma cells have a great natural tendency to infiltrate the most The Reese–Ellsworth Classification, developed in 1963 readily accessible spaces, these being the vitreous, (Reese and Ellsworth, 1963), remains the classification subretinal fluid, anterior segment and meningeal sheaths system most widely used.Although clearly outmoded, of the many systems proposed in recent years, none has yet found consensus within the medical community.The Reese–Ellsworth Classification is based on intraocular tumor staging and globe salvage prediction after external beam radiation, survival not being taken into account.The failure of external beam radiotherapy to effectively treat peripheral tumors and the difficulty of treating vitreous seeding at that time lead to these factors being determinant in staging the severity of the disease.Of the most recent staging proposals, the International Intraocular Retinoblastoma Classification (ABC Classification) constitutes that most commonly used and of greatest prognostic value (Murphree, 2005) (Table 1). This classification stages intraocular tumors according to their prognosis after first-line chemotherapy and adjuvant focal therapy.It consists of five groups (A, B, C, D, E) in descending order of favourable prognosis, Figure 5 Two small tumors away from the macula and optic disc, taking into account the size of the tumors, their group A retinoblastoma (ABC Classification).

Table 1 International intraocular retinoblastoma classification (ABC classification) Group A – very low risk Tumors 3 mm or smaller Eyes with small discrete tumors away Confined to the retina from critical structures >3 mm from the foveola >1.5 mm from the optic nerve No vitreous or subretinal seeding

Group B – low risk Tumors not in group A Eyes with no vitreous or subretinal seeding and No vitreous or subretinal seeding discrete retinal tumor of any size or location Subretinal ﬂuid >5 mm from the base of the tumor

Group C – moderate risk Seeding local, ﬁne and limited Eyes with only focal vitreous or subretinal seeding and Treatable with a radioactive plaque discrete retinal tumors of any size and location Tumors discrete and of any size and location Up to one quadrant of subretinal ﬂuid

Group D – high risk Massive and/or diffuse intraocular disseminated disease Eyes with diffuse vitreous or subretinal seeding and/or massive, More than one quadrant of retinal detachment nondiscrete endophytic or exophytic disease. Fine greasy vitreous seeding or avascular masses Eyes with more extensive seeding than Group C Subretinal seeding, plaque-like

Group E – very high risk eyes Irreversible neovascular glaucoma Eyes that have been destroyed anatomically or functionally Massive intraocular hemorrhage by the tumor.Eyes with one or more than the following: Aseptic orbital cellulitis Tumor anterior to anterior vitreous face Tumor touching the lens Diffuse inﬁltrating retinoblastoma Phthisis or prephthisis

Murphree AL (2005).Intraocular retinoblastoma: the case for a new group classiﬁcation. Ophthalmol Clin N Am 18: 41–53.

Oncogene Diagnosis and current management of retinoblastoma A Balmer et al 5344 lymphatic pathway (conjunctiva, eyelids).The tumor may also invade the orbit directly through the sclera or by following the orbital canals of the ciliary arteries and nerves.

Risk factors for metastatic disease

The greatest risk factors for metastatic disease are optic nerve or orbital invasion (Kopelman et al., 1987; Messmer et al., 1991). The risk of metastasis through optic nerve invasion depends on the stage of tumor penetration.The mortality rate is 50–85% (Uusitalo et al., 2001) if tumor cells have reached the surgical resection line, 13–69% if posterior to the lamina but not reaching the surgical resection, insigniﬁcant if anterior to the lamina cribrosa. Figure 6 Tumor with focal subretinal seeding and discrete Massive choroidal invasion is generally considered the inferior retinal detachment, group C retinoblastoma (ABC only other risk factor, the association of optic nerve and Classiﬁcation). choroidal invasion carrying the greatest risk (Shields et al., 1993a; Khelfaoui et al., 1996; Chantada et al., 1999). Orbital extension of retinoblastoma can lead to systemic dissemination via the blood vessels, lymphatic system or along the visual pathway to the brain.Orbital invasion is considered an important risk factor (Kopel- man et al., 1987) but modern aggressive therapy may prolong survival. Anterior chamber invasion does not increase the mortality rate, in spite of the risk of vascular dissemination.

Second nonocular primary tumors

The Rb1 mutation present in all cells of a patient with retinoblastoma predisposes them to developing other nonocular malignant tumors, albeit with a predilection Figure 7 Phthisis and irreversible neovascular glaucoma, ultimate complications of an untreated retinoblastoma, group E retino- for certain tissues. blastoma (ABC Classiﬁcation). Second primary tumors are the greatest cause of death in these patients, rather than the retinoblastoma itself (Abramson, 1999; Fletcher et al., 2004). The cumulative incidence of these additional tumors is around 1% per of the optic nerve.Retinoblastoma can thus develop in year, thus 50% after 50 years’ evolution (Abramson, three directions: 1999).Radiotherapy greatly increases the risk, particularly if administered before the age of 1 year (Abramson Anteriorly via the vitreous or subretinal space to the and Frank, 1998). anterior segment, reaching the ciliary body and According to a study by Abramson et al.(2001), the anterior chamber and creating a pseudohypopyon. most common sites of second nonocular tumors are, in Posteriorly, step by step towards the optic nerve and order of frequency: soft head tissue (24%), cranium cephalo-rachidien liquid, usual gateway to endocra- (18%), skin (15%), brain (8%) and others (25%). nial dissemination. Extraocular extension to the orbit via the choroid and sclera. Treatment

Past the barrier of the lamina cribrosa, inﬁltration may In the early 20th century, a child suffering from continue via the retrolaminal portion of the optic nerve retinoblastoma had little chance of survival.Progress to the subarachnoid space and further, transported by in the management of this disease has lead to a steady the cephalo-rachidien ﬂuid, to the various cerebral increase in the survival rate, from 30% in the 1930s to structures.Metastatic dissemination may also occur 80% in the 1960s.In specialized centers today, almost via the vascular pathway (orbit, optic nerve) or 95% of these children can be saved thanks to modern

Oncogene Diagnosis and current management of retinoblastoma A Balmer et al 5345 therapeutic strategies: systematic enucleation, external disorders or leukopenia, and as yet undetermined, beam radiotherapy, focal treatments, chemotherapy, possibly dangerous, long-term complications.Only stereotactic conformal radiotherapy. strictly necessary agents should be administered and at Management of a child with retinoblastoma requires a dosage that is truly effective, limiting the number of constant re-evaluation of the situation according to the cycles to that needed to achieve the aim of treatment response to treatment, with survival the primary aim, that is reduction of tumor volume to allow focal followed by globe salvage and the best possible visual therapies.A permanent response is almost never function. achieved with chemotherapy alone. According to Shields et al.(1997), primary chemotherapy comprising two or more agents will reduce Chemotherapy tumor volume by over 50% within a few weeks (Figure 8), dry out a retinal detachment and permit Treatment approaches changed notably in the 1990s consolidation with methods other than external beam with chemotherapy or, more exactly, chemoreduction, radiotherapy. gradually replacing external beam radiation and enuclea- The choice of agents, their combination and dosage, tion as ﬁrst-line treatment, shrinking the lesions until varies from one center to another.Most institutions accessible to adjuvant focal tumor control (Figure 8). utilize vincristine, carboplatin and an epipodophyllo- This new strategy has reduced the frequency of enuclea- toxin, either etopside or teniposide.Cyclosporine A is tion and spared the complications associated with sometimes associated to prevent multidrug resistance primary external beam radiation, in particular the risk (Chan et al., 2005). The number and frequency of cycles of second nonocular radiation-induced cancers, a risk also varies. particularly high during the ﬁrst year of life. Systemic chemotherapy is not, however, without its own hematologic side effects such as coagulation Focal treatment methods

The different focal treatment modalities are given in Table 2.

Cryotherapy and photocoagulation (Argon Laser, Diode Laser, Xenon) are indicated for simple, effective and permanent control of small tumors, new tumors, or in the case of a localized relapse (Abramson, 1989).

Chemothermotherapy

Heat increases the permeability of the plasmatic membrane to antimitotics, thus reinforcing their cytoxic effect.Carboplatin is administered intravenously 1 or 2 h before the thermotherapy.Infrared radiation from a diode laser, this mounted on a surgical microscope, is focused on the tumor through a contact lens for a period of several minutes (5 to 30 according to the volume of the tumor).The aim is to deliver a temperature of 41–441.A second session, this thermotherapy only, is carried out between 4 and 7 days later.The whole cycle is repeated two or three times at 28-day intervals until complete tumor control is achieved.

Table 2 Focal treatment methods Cryocoagulation with/without conjunctival incision Photocoagulation : transpupillary or transscleral Chemothermotherapy

Thermotherapy or hyperthermia Brachytherapy (ruthenium, beta and iodine 125 rays, gamma rays) Stereotactic conformal radiotherapy Figure 8 Group D retinoblastoma, before (a) and after (b) Accelerated proton beam irradiation chemoreduction.

Oncogene Diagnosis and current management of retinoblastoma A Balmer et al 5346 Thermotherapy limiting their use to the treatment of small tumors under 6 mm in thickness. Thermotherapy, or hyperthermia, consists of utilizing the cytoxic effect of heat by raising the temperature of the tumor to over 451, using infrared radiation from a Stereotactic conformal radiotherapy diode laser (Shields et al., 1999). This method of treatment can be used alone for the treatment of small When none of the above focal treatment modalities is tumors, or in conjunction with chemotherapy or radio- applicable, external radiation therapy may be necessary. therapy.If used in conjunction with these latter, a Ideally, radiotherapy should be applied only to the slightly lower temperature is sufficient (see above). tumor itself, sparing the surrounding structures.This is Tumors under 3 mm in diameter and 2 mm in thickness now possible with stereotactic conformal radiation usually respond well to thermotherapy alone. therapy for which new apparatus has been designed, a multileaf photon 6 MV collimator.A sophisticated system is required, comprising a custom-molded plastic Brachytherapy or plaque radiotherapy mask, scanner for treatment planning, contact lens with suction cup to immobilize the globe and adapted to the Radioactive plaques (Iodine-125, Ruthenium-106) mask, multiple conformal static fields.The radiation (Shields et al., 1993b) can be used for the primary dose delivered is 50.4 Gy in 1.8 Gy fractions, represent- treatment of medium sized tumors (under 16 mm in ing 25–28 sessions. diameter and 9 mm in thickness), but more often as a Tumors in Groups B and C, with residual active secondary measure after prior failed treatment or in the tumoral activity in the foveal or peri/epi-papillary region case of a relapse.Cobalt-60 plaques have been largely after chemoreduction, are candidates for secondary abandoned due to their high-energy gamma rays stereotactic conformal radiotherapy. preventing all shielding and consequently giving off radiation in all directions. Currently, the most widely used plaque is the Iodine- Accelerated proton beam irradiation 125.The low-energy gamma rays allow a unidirectional, shielded radiation field (Figure 9). Ionizing radiation for destroying tumor tissue is well Ruthenium plaques may also be applied.These emit known.Charged protons have a well-defined stopping high-energy beta rays but with poor tissue penetrance, point and reach maximum ionisation density at the end

Figure 9 Above, radioactive plaque with Iodine-125 seeds (c) and silicone shell (b).A gold foil prevents collateral radiation damage (a).Below, tumor before ( d, showing plaque indentations) and after irradiation (e).

Oncogene Diagnosis and current management of retinoblastoma A Balmer et al 5347 of their path, a point termed ‘Bragg Peak’.Modulation of the proton beam accelerator produces a succession of Bragg Peaks calculated to create a uniform ionisation plateau at the desired spot within the tumor, causing maximum damage where desired with minimal collateral tissue effect. The radiotherapy equipment comprises a beam modulator and collimator, and a stereotactic couch fitted with a custom-molded plastic mask to immobilize the patient’s head.Tumor localization is assured by suturing four tantalum rings to the sclera as reference points, marking the tumor edges (Zografos, 2002). The precise indications for proton beam irradiation are in evolution but seem, at first sight, the same as those for stereotactic conformal radiotherapy, including orbital irradiation after enucleation with positive histo- pathology for tumor cells present at the surgical resection line of the optic nerve stump.More specific indications may develop with time, but proton beam radiotherapy requires the child’s cooperation and is not suitable for children under 3 1/2 years.

Enucleation

Enucleation has become less common with earlier diagnosis and better alternative therapies, but remains the treatment of choice for advanced cases (massive involvement of the retina/vitreous, rubeosis iridis, secondary glaucoma) with no visual potential or with high risk of dissemination (massive choroidal or optic nerve invasion, anterior segment involvement, extraocular extension).

External radiotherapy

External beam irradiation is no longer considered a ﬁrst- line conservative treatment due to its important long- term side effects.It remains indicated in advanced bilateral cases with or without vitreous seeding, or in the case of a relapse inaccessible to conservative focal treatment methods. The habitual total dose administered is 40–50 Gy, delivered in fractions of 1.8 Gy through lateral or anterior ﬁelds, using a lens-sparing technique whenever possible.

Future management

Proton beam therapy may become common practice in future management of retinoblastoma, the advent of second-generation collimated Gantry machines allowing the irradiation of very small tumors. Figure 10 Two tiny lesions (arrows) (a) in a case of germinal Local delivery of chemotherapeutic agents (carbopla- retinoblastoma with positive family history in a newborn.A tin) by periocular (subtenon) or intraocular injections 3-week preterm delivery was programmed.Response after laser has been experimented in animals (Murray et al., 1997; photocoagulation (b) and ﬁnal result (c) with tumors totally Van Quill et al., 2005) and used in selected retinoblas- destroyed. toma patients with some success.It is not, however, without risk and at the present time does in no way

Oncogene Diagnosis and current management of retinoblastoma A Balmer et al 5348 present an alternative to systemic chemotherapy. Conclusion Further study is needed to determine fully the safety and applicability of these procedures. The best treatment is, and will always be, early Molecular therapy for retinoblastoma, taking advan- treatment.This signifies early diagnosis.In cases of tage of the specific genetic defect in retinoblastoma, is positive family history all members of the family should currently under study (Huang et al., 1988; Xu, 2003; be screened for retinoblastoma and all newborns at Chevez-Barrios et al., 2005). birth.Pregnancies within a family at risk require special Preimplantation genetic diagnosis, following an accu- monitoring with antenatal ultrasonography, genetic rate mutation analysis procedure for retinoblastoma testing and, if in doubt, a 3 to 4-week preterm delivery gene mutation sensitive at the single-cell level, is possible (Figure 10). today for in vitro fertilization in order to achieve In children, and until proved otherwise, the risk of pregnancies without retinoblastoma (DerKinderen retinoblastoma should always be forefront in the et al., 1990; Xu et al., 2004; Simpson et al., 2005). presence of leukocoria, strabismus or any other un- Photodynamic therapy (PDT), based on the use of explained sign.The family, gynecologist, pediatrician or nontoxic photosensitizers activated with a visible non- primary care physician are the first likely to be ionising laser light may represent an alternative non- confronted with these signs, well before the multi- mutagenic therapy.First experimental data indicate that disciplinary specialized team.This emphasizes the PDT could efficiently slow down some retinoblastoma importance of awareness at all levels, both public and growth, with no acute toxicity (Aerts et al., 2005). professional.

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Oncogene