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Retinoblastoma: Current Concepts

S.K. Arya, Prof. Sunandan Sood

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Topics

Enucleation is a common method for managing retinoblastoma. Enucleation with long stump of optic nerve should be done if advanced disease with no hope for salvageable vision, or if invasion of the tumor into ON, choroid or orbit is possible. Eyes with secondary glaucoma, pars plana seeding or anterior chamber invasion are generally best managed with enucleation. External beam radio-therapy is very useful because of radio-sensitive nature of retinoblastoma. It is done for treating advanced retinoblastoma with massive vitreous seeding. This can be employed by irradiating whole eye or by lens sparing technique. Tumor recurrence after radiotherapy is usually within 1 to 4 years. The incidence of second cancer after radiotherapy increases to 35% from 6% without radiotherapy. Cryo therapy is useful for size less than 3.5 mm and 2.0mm in thickness with no evidence of vitreous seeds. It is done by triple freeze thaw technique.

Laser photocoagulation is done for small posterior RB less than 4.5 mm in size and 2.5 mm in thickness without vitreous seeding. Argon, Diode or Xenon-arc laser can be used with 70% tumor control rate and 30% recurrence rate. Radio-active plaque (Brachy therapy) with Cobalt 60, Iridium 192, Iodine 125, Isotopes, 35 and 40gy is delivered to all visible disease. It is done for tumor less than 15mm in area and 12mm from optic disc or fovea and when there is vitreous seeding or tumor is too large to be treated by cryo-therapy. Thermotherapy is a method of delivering heat to the eye using ultrasound, microwave or infrared radiation. The goal is to deliver a temperature of 42oC to 60oC to spare the retinal vessels from photo-coagulation. Heat has synergistic effect with both chemotherapy and radiation therapy for treating retinoblastoma. This therapy is helpful for smaller tumors less than 3mm. Chemotherapy is suited for small tumors adjacent to the fovea and ON where radiation or laser photocoagulation will cause more profound visual loss.

Intravenous chemoreduction is a method of reducing tumor volume to allow for more focused, less damaging, therapeutic measures. The chemotherapy used is carboplatin, etoposide and vincristine. This regimen of six cycles has ocular salvage rate of 70%. After chemoreduction, regressed tumor scar needs consolidation with focal measures for complete control usually at 2nd or 3rd cycle. Subconjunctival chemoreduction specially carboplatin, which penetrates sclera, has shown encouraging results in animals and human trials but it needs consolidation with focal therapy also. Systemic chemotherapy is needed for metastasis to ON, choroid, orbit and distal organs. The drugs used are cyclophosphamide, vincristine, etoposide and carboplatin for 6-18 months depending upon circumstances. Orbital exenteration is used for orbital recurrence after child has received a maximum acceptable dose of radiation and chemotherapy.

Photo-dynamic therapy works by transferring energy from specific wavelength of light causing the creation of highly reactive singlet oxygen species. These agents (Benzo porphyrin) destroy membrane of cells that contain photo-sensitive dye. Patients should be followed every 4 months until 2 years of age, every 6 months from 2-5 years and every year after age of 5 years. All siblings and parents of retinoblastoma patients should undergo examinations with dilated pupils, to allow earlier examination and treatment of children at presymptomatic disease stage.

The prognosis for life and vision in patients with retinoblastoma has vastly improved over the past century primarily because of earlier detection of the disease as well as improved treatments. One hundred years ago, retinoblastoma was nearly always fatal. Gradually the prognosis improved and approximately 30% of affected patients survived in 1930s, 80% in 1960s and nearly 95% in the 1990s. Bad prognostic signs are delay in diagnosis, recurrent disease, tumor invasion in optic nerve, vitreous, seeding, increased volume of choroid and involvement of sub-arachnoid space.

S.K. Arya1,
Prof. Sunandan Sood2

1Reader,
2Head, Department of Ophthalmology,
Govt. Medical College,
Sector 32, Chandigarh.



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