Eye Melanoma vs. Retinoblastoma

Melanoma (Eyes)

• The most common eye malignancy, though still rare
• More prevalent in individuals >60 years old and of Caucasian descent compared to African descent
• Originates from melanocytes
• Slow-growing with poor prognosis
• Can metastasize to the liver, less commonly to lymph nodes

Retinoblastoma (Eyes)

• Associated with chromosome 13 Rb gene; 10% are familial cases
• Occurs in children
• Rarely metastasizes

Melanoma vs. Retinoblastoma Treatment

• Melanoma treatments include excision (small), enucleation (large), and exenteration (extraocular)
• Retinoblastoma treatments include cryo and photo minimally invasive procedures, enucleation (large), cryotherapy, and photocoagulation

Radiation Therapy (RT) for Eye Conditions

• Melanoma RT: Strontium-90 eye plaque, EBRT (Proton 70 CGE, SRT/IMRT)
• Retinoblastoma RT: Radioactive plaque for tumors <4mm (40 Gy in 2-4 days), EBRT/IMRT (40 Gy in 4 weeks), Proton (40-45 CGE + chemo)

Chemotherapy for Retinoblastoma

• Used in early stages for chemoreduction
• Common regimen: Carboplatin + Etoposide + Vincristine (CEV)
• Used with proton therapy (40-45) to avoid enucleation

Anatomy of the Eye (3 Layers)

• Fibrous Tunic: Outer layer (cornea and sclera; no melanoma)
• Vascular Tunic (Uvea): Middle layer (choroid, ciliary body, pigmented epithelium, iris)
• Retina: Innermost layer (receives oxygen from choroidal and retinal blood vessels)
• Anterior and posterior chambers contain aqueous humor
• The posterior cavity behind the lens is filled with vitreous body
• The lens is connected to the ciliary body by a suspensory ligament

Additional Eye Anatomy Notes

• Macula and optic disk are key structures in retinoblastoma
• The conjunctiva the epithelium in-folding to protect sclera in melanoma
• Ocular melanoma can be uveal (choroidal) or retinal

Important Notes on Eye Treatments

• Strontium-90 for melanoma and EBRT for retinoblastoma aren't common
• All proton treatments involve 1-2 beams
• Chemotherapy is used for retinoblastoma only
• SRT is used for small melanomas only

RT Summary for Eyes

• Melanoma plaque treatment is indicated for small lesions near the retina or choroid, though plaque therapy is not common
• Retinoblastoma plaque treatment is indicated for tumors <4 mm near the macula or optic disk that are localized
• Melanoma plaque prescription: Strontium-90 delivers >80 Gy in 3-7 days at 40% activity at 1 mm
• Retinoblastoma plaque prescription: Iodine-125 delivers 40 Gy in 2-4 days

Radiation Therapy Techniques

• Melanoma: 1-2 beams, 70 CGE
• Retinoblastoma: 1-2 beams, 40-45 CGE accompanied by CEV to avoid enucleation
• Small melanomas: treated with SRT (6.2Gy*10 fr to GTV), using a gazing target to limit eyeball movement and reduce lens dose
• IMRT is used for large, inoperable melanomas

IMRT Specifics

• Supine position, head straight
• Head rest + immobilisation mask
• CT/MRI for image registration
• 6-8 MV energy
• Organs at Risk (OARs): optic chiasm, contra lens and nerve, brainstem, temporal lobe
• Retinoblastoma (less common): 4 fields, 40 Gy in 20 fractions

Signs and Symptoms of Eye Conditions

• Melanoma: cataract, secondary glaucoma, retinal detachment
• Retinoblastoma: white reflex in pupil, pupil doesn't respond to light
• General symptoms: pain, visual problems

Investigation Techniques

• Fundoscopy (using ophthalmoscope)
• Orbit and regional lymph node palpation
• Ultrasound & Biopsy (only for melanoma)
• Look for proptosis

Dysthyroid Eye Disease

• Steroid treatment; consider RT to treat both eyes for recurrence
• 3DCRT with paired wedged lateral fields angled slightly posteriorly (app. 5°)
• No steroid with RT initially (1 Gy to midline, then increase to 1.73 Gy* 11fr, to total of 20 Gy)
• With concurrent steroid and RT: 2 Gy* 10 fr
• Increase steroid dose or stop RT if eye inflammation

Reactive Lymphoid Hyperplasia

• Steroid use
• RT to only the involved eye for persistent signs and symptoms.
• Involves 3DCRT with paired wedged anterior/lateral fields (2 Gy* 15 fr to total of 30 Gy).

Anatomy of the Ear

• External: EAM (SCC), pinna (all malignant)
• Middle: petro mastoid / tympanol-tubal (SCC if malignant), auditory bones
• Inner: cochlea (only benign)

Signs and Symptoms of Ear Conditions

• External and middle: otorrhea, tender mastoid, frank tumor
• SCC: Spread uncommon
• Paraganglioma: Tympanic nerve (IX)
• Internal: Acoustic neuroma: Loss of balance (VIII), headache
• General: tinnitus, hearing loss, facial palsy (VII) (T2)

Investigation

• Otoscope
• Audiogram to check for hearing loss
• Examine VII cranial nerve

External/Middle management

• Biopsy/ neck palpation/ CT/ MRI
• Surgery: Total temporal bone resection + Mastoidectomy
• RT: For intracranial (T3) in-operable or adjuvant (60Gy 20fr); definitive : 60 Gy in 30 fr
• Adjuvant vs definitive: 3Gy vs 2Gy per fr, total dose same (60 Gy)
• All 2Gy/ fr except SRT for melanoma, and dysthyroid eyes
• Acoustic neuroma management = Surgery / SRS to arrest growth (OAR brainstem)
• Eye if benign
• Middle ear = ipsilateral wedged pair and appositional electron boost
• Dysthyroid eye diseases = laterally opposing
• Reactive lymphoid hyperplasia = ant. & lat.
• Middle ear SCC using wedged pair (3DCRT)

Paraganglioma/ Glomus Tumor (Benign Middle Ear Tumor)

• Can secrete hormones
• Affect tympanic nerve
• Highly vascular
• Signs and Symptoms: dysphagia (compress XI nerve), tinnitus
• Cranial nerve: 7,8,11

Pituitary gland

• Treatment depends on whether it is a prolactinoma, other adenomas, or symptomatic

Pituitary gland Treatment

• Asymptomatic: observe
• Prolactinoma: medicine -> surgery if no response
• Others: surgery -> further RT or medicine if hormone level still abnormal
• Multidisciplinary approach: Neurosurgeon + Endocrinologist + Radiation oncologist
• Surgery as 1st line (hormone related): small tumor (trans-sphenoidal/ nasal), large (trans cranial), hypophysectomy (extrasellar spread, overproduction of hormones)
• Complications: Meningitis / CSF spread

Pituitary Radiotherapy

• Control residual tumor post-op
• Inoperable cases
• Biochemical control (hormone regulation)
• Reduce tumor size
• Reduce mass effect

Adrenal Gland

• Pheochromocytoma originates from Chromatin cells and involves the MEN gene
• Presentation
  • Challenges: Respiration, Radioresistant

RT Fractionations

• IMRT: generally for larger tumors

Conventional Fractionation (2Gy * 20fr)

• Retinoblastoma (carcinogenesis)

Conventional Fractionation (2 Gy * 10 fr)

• Dysthyroid eye disease (RT with steroid)

Conventional Fractionation (2 Gy* 15 fr)

• Reactive lymphoid hyperplasia (RT with steroid)

Conventional Fractionation (2Gy * 30fr)

• Ext/Mid ear [RT Alone] (No-op Adjuvant becomes 60 Gy in 20 fr)

Conventional Fractionation (2Gy * 35fr)

• Skin BCC/SCC

Conventional Fractionation (1.8Gy * 30 fr)

• Functional pituitary

Hypofractionation (3Gy * 15fr)

• Skin BCC/SCC
• Non-functional pituitary (Or 50 Gy in 10 fr)

Hypofractionation (3Gy * 20fr)

• In-op/ residual disease post surgery/ T3 intracranial ext and middle ear

Hypofractionation (6Gy * 5 fr)

• Skin melanoma (Radioresistent)

SRS/SRT/SBRT: generally for small tumors

• SRS = 12-15 Gy at 50-80%IL
  • Inner ear (Smaller PTV = Less side effects)
  • Pituitary (14 Gy at 60%IL)
• SRT = 62Gy in 10 fr
  • Ocular melanoma
• SBRT = 20-25 Gy
  • Adrenal

PT: mainly head cases

• 1-2 Beams
  • Ocular melanoma (70 CGE)
  • Retinoblastoma (40-45 CED)
• 2-3 Beams
  • Pituitary (No dose given)