Retinoblastoma

Bharat R Agarwal
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Tumor Staging
For the purpose of treatment, retinoblastoma is divided into intraocular and extraocular disease.
Intraocular: Tumor is localized to the eye, it does not extend beyond the eye or to other parts of the body.
Extraocular: Tumor extends beyond the eye. It may be limited to the tissue around the eye, or it may spread to the CNS or other parts of the body.

Reese and Ellsworth have classified intraocular Retinoblastoma as follows:
Group 1 : very favorable for maintenance of sight.
- Solitary tumor, smaller than 4 disc diameters, all at or beyond the equator.
- Multiple tumors, none bigger than 4 disc diameters, all at or beyond the equator.
Group 2 : favorable for maintenance of sight.
- Solitary tumor, 4-10 disc diameter in size, at or beyond the equator.
- Multiple tumors, 4-10 disc diameter in size, behind the equator.
Group 3: Possible for maintenance of sight.
- Any lesion anterior to the equator
- Solitary tumor larger than 10 disc diameter, posterior to the equator.
Group 4: Unfavorable for maintenance of sight
- Multiple tumors, some larger that 10 disc diameter in size
- Any lesion extending anterior to the ora-serrata.
Group 5: Very unfavorable for maintenance of sight
- Massive tumors involving more than one half of the retina.
- Vitreous seeding
(About 90% of patients present with Group5 disease in one or both the eyes)

The treatment options of retinoblastoma requires a great deal of expertise of the response of the disease at its various stages, and the potentials of each treatment option. Treatment has undergone paradigm of change along the past 50 years. From a near fatal disease, it now has a 95% survival. The current management options target organ salvage and vision salvage. The current treatment guidelines are set as per the International Retinoblastoma Classification and TNM classification of the tumor and are followed uniformly across the globe.

1.Chemotherapy: Systemic chemotherapy is now the mainstay and generally the 1st line of management. It aims at reducing the size of the tumours (chemoreduction) to allow for consolidation treatment with other agents to eradicate the tumours. Depending on the response to chemotherapy, other modalities are used in conjunction. Drugs used are Vincristine, Etoposide, carboplatin, cyclosporine .

2. Sequentially aggressive local treatment (SALT) :
This includes trans pupillary thermotherapy( heating the Tumor) , retinal lasers , cryotherapy (freezing the Tumor) and may be used alone in very small tumors or in conjunction with chemotherapy for larger ones. These technique targets organ as well as vision preservation.

Regional chemotherapy: Intravitreal chemotherapy (melphalan) may be given in selective cases . Periocular topotecan is another modality used. Recently, supra selective chemotherapy administered via the ophthalmic artery is being increasingly used across the centres . This technique avoids systemic side effects of chemotherapy and avoids removal of the eye as well. This technique has been aptly christened "chemo surgery”. Melphalan, carboplatin and topotecan have been used for this technique

3. Enucleation: Upto 25% -50% of the eyes may need eye removal or enucleation depending on the severity of the disease. Getting a long optic nerve stump (atleast 15 mm) is very important, so is proper histopathology to confirm the tumor extent.A ball like orbital implant is placed in the socket during primary surgery. A prosthetic eye can be fitted as early as 6 weeks post operative with excellent outcomes.(FIGURE 3: Post enucleation prosthesis) Generally, these procedures don't interfere with any subsequent Tumor treatment modalities.

4: Radiotherapy for retinoblastoma has a limited role in the current day scenario. It is generally resorted to in chemo resistant cases. It can be in the form of plaque brachytherapy for unifocal medium sized lesion or external beam radiation for multifocal disease with vitreous seeds.

Figure 3: Right eye ocular prosthesis after enucleation surgery and orbital implant


The goals of therapy are:
- To cure the disease
- To preserve as much sight as possible

I] TREATMENT FOR INTRAOCULAR RETINOBLASTOMA
The various options are:
- Enucleation: if tumor is large or useful vision is not expected.
- External beam radiation between 3500 to 4600 cGY, delivered in 17-25 fractions over 4-5 week period.
- Cryotherapy: For lesion smaller than 4-disc diameter in the anterior portion of retina, in addition to radiation or in place of photocoagulation.
- Laser Photocoagulation: For posteriorly located tumors smaller than 4-disc diameter distinct from the optic nerve head and macula.
- Systemic Chemotherapy: To reduce tumor load and avoid long-term effects of radiation therapy for patients with intraocular tumors not amenable to cryotherapy or photocoagulation alone.

Unilateral disease
- Enucleation: It is the standard therapy as most unilateral tumors are massive.
- Radiation, cryotherapy, photocoagulation, systemic chemotherapy are useful for smaller size tumors.

Bilateral disease
- Since one eye may be more severely involved as compared to the other eye, the standard treatment is to enucleate the more involved eye. However, if there is a potential for sight in both eyes, bilateral irradiation with close follow-up for response is indicated.
- Systemic chemotherapy followed by cryotherapy/photocoagulation is still experimental.

II] TREATMENT FOR EXTRAOCULAR RETINOBLASTOMA
There is no clear-cut therapy, however orbital irradiation with chemotherapy may be useful with/without intrathecal methotrexate.

All siblings of patients with Retinoblastoma should be examined periodically and DNA polymorphism analysis should be done.


Retinoblastoma Retinoblastoma 01/03/2001
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