Treatment Paradigm

Question 1

What is the Tx paradigm for very low/low risk unilat intraocular RB?

Answer 1

Unilat intraocular RB Tx paradigm: Chemoreduction for larger tumors involving macula → focal therapy

Question 2

What are some focal therapies used for RB?

Answer 2

Cryotherapy, photocoagulation (laser), ophthalmic artery chemosurgery (OAC), plaque brachytherapy

Question 3

When can cryotherapy/laser be used in RB?

Answer 3

Small lesions, at least 4 disc diameters from the fovea/optic disc

Question 4

Which Tx modalities have significantly diminished the role of EBRT and systemic therapy in the Tx of RB over the last 10 yrs?

Answer 4

OAC and intravitreous chemotherapy have replaced the role for RT more and now offers hope of eye preservation for even group D tumors.

Question 5

What is the current management of unilat RB based on the international RB groupings?

Answer 5

Group A: focal therapy (laser, cryotherapy, plaque brachytherapy)

Group B: focal therapy; OAC f/b focal therapy for macular tumors

Group C: OAC +/– intravitreous chemotherapy

Group D: OAC +/– intravitreous chemotherapy

Group E: enucleation, with consideration or adj Tx

Question 6

When is EBRT now typically used in the management of RB?

Answer 6

Following enucleation with microscopic residua at the cut section of the optic nerve or sclera, or palliation of bulky metastatic Dz

Question 7

What are indications for enucleation?

Answer 7

Painful glaucoma, buphthalmos, ant chamber seeding, diffuse infiltrating RB, phthisis bulbi

Question 8

How is bilat RB managed?

Answer 8

Individualize the Tx for each eye (bilat eye preservation, if possible). In no case is EBRT used as primary therapy for bilat RB.

Question 9

What is the eye preservation rate for unilat Group D tumors with OAC alone?

Answer 9

83% (Abramson D et al., JAMA Ophthalmol 2015)

Question 10

How was EBRT given for RB, and what are the volumes irradiated?

Answer 10

4–6 MV IMRT/3D, proton therapy, electron therapy if available to entire globe + 5–8 mm of optic nerve (spare lens and iris for lower stages), 36–45 Gy; 0.5-cm bolus if needed.

Question 11

What RT fields/setups were used for unilat vs. bilat RB?

Answer 11

Old standard for unilat Dz was 4 ant oblique fields and for bilat Dz opposed lat + ant oblique fields. Advanced techniques tended to use ant/ant oblique angles.

Question 12

What chemo agents are employed in OAC?

Answer 12

Melphalan, carboplatin, and/or topotecan

Question 13

What are the indications for episcleral brachytherapy? What is the dose used?

Answer 13

Solitary lesion 6–15 mm base diameter, ≤10 mm thick, >3 mm from disc/fovea; 40–45 Gy to apex, 100–120 Gy to base

Question 14

What isotopes and plaque sizes are used in episcleral brachytherapy for RB?

Answer 14

I-125 or Ru-106 (more uniform loading, lower energy [beta] and less dose to ant ocular structures), diameter of tumor + 4 mm (2-mm margin around the tumor)

Question 15

What are the major complications of EBRT in the Tx of RB?

Answer 15

Induction of secondary malignancies (particularly in pts with heritable RB); damage to retina, optic nerve, lacrimal gland, and lens; midface hypoplasia with retardation of orbital bone growth when given at age <12 mos.

Question 16

What is the 2nd malignancy rate in heritable RB treated with RT vs. no RT?

Answer 16

With RT: 4% at 10 yrs, 18% at 35 yrs, 50% at 50 yrs

Without RT: 15%–35% rate at 50 yrs, mainly sarcomas (ST and osteosarcoma) and melanomas

Question 17

Is the risk of 2nd malignancy also increased in sporadic RB treated with RT?

Answer 17

Yes, but minimally—5% at 50 yrs (Wong FL, JAMA 1997)

Question 18

What are the complications from episcleral plaque therapy?

Answer 18

Retinopathy, maculopathy, glaucoma, and papillopathy

Question 19

In what manner and how often should pts with bilat RB be screened for trilat RB?

Answer 19

With biannual MRI of the brain for at least 5 yrs.

Question 20

What are appropriate treatment approaches for multifocal retinoblastoma, or tumors close to the macula or optic nerve with preservation of vision?

Answer 20

Appropriate treatment options include external beam radiotherapy or the alternative of chemotherapy followed by focal therapy if the target size and location becomes appropriate. The rationale for this approach is to optimize the target volume for radiotherapy and thereby reduce the side effects associated with external beam radiotherapy including second malignancy and facial hypoplasia.

Question 21

When is the focal therapy of photocoagulation appropriate for retinoblastoma?

Answer 21

Focal photocoagulation, which uses a laser to obliterate the retinal blood vessels feeding the tumor, can be used as primary therapy for tumors ≤4.5 mm at the base and ≤2.5 mm thick and not close to the macula or optic disc, and without vitreous seeding. It can also be used for a local recurrence postradiation or in conjunction with chemotherapy.

Question 22

When is cryotherapy most appropriate for retinoblastoma?

Answer 22

Cryotherapy is most appropriate as primary therapy for small tumors anterior to the equator, without vitreous seeding, and can be reached by the cryoprobe. It can also be used for a local recurrence postradiation or in conjunction with chemotherapy.

Question 23

When is plaque radiotherapy appropriate for retinoblastoma?

Answer 23

Plaque radiotherapy is appropriate as primary treatment for a solitary 2- to 16-mm basal diameter and less than 10-mm thick unilateral lesions located greater than 3 mm away from optic disc or fovea. It is often used following chemotherapy and some propose a dose reduction of 25 to 30 Gy to the apex following chemotherapy. The typical dose used is 40 Gy to the tumor apex.