31 Uveal Melanoma

Uveal Melanoma

12

THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 15/04/2020

accepted margins, some have recommended that extra care is required for cases in which the lateral extent of the tumour is particularly large. Individual quality assurance of the surface dose rate homogeneity can help in avoiding critical underdosages in the target volume.

Specific patterns of tumour regression are typical for different tumour types and also vary with the treatment method. A rapid complete remission with a sharply delineated flat white scar may be achieved but more often, tumour regression takes place slowly resulting in a white scar at the margin and a prominent grey mass in the centre (“grey mouse”). Sometimes there is almost no change in tumour extension and height for years.Therapeutic decisions are usually taken if tumour regrowth is suspected because of tumour enlargement on ophthalmoscopy, ultrasonography, or fluorescence angiography or because of a decrease in ultrasonographic reflectivity. Follow-up after eye-conserving treatment is usually based on ophthalmoscopy, and ultrasound. Fluorescein angiography (FA) and optical coherence tomography (OCT) are useful for early detection of ischaemic changes leading to radiation retinopathy, maculopathy and optic neuropathy. Visual loss in the treatment area gradually occurs over the course of 2-3 years. Recent data have shown that use of exclusive plaque brachytherapy is preferred to brachytherapy plus routine use of adjuvant TTT in view of the better residual visual acuity . However, in cases of underdosage to the tumour area, especially for posterior disease, the use of adjuvant TTT could be taken in the account for improving tumour regression and local control. Eye plaque brachytherapy is mainly based on Ruthenium-106 and Iodine-125. In 2002, the Collaborative Ocular Melanoma Study reported that local treatment failure occurred in 10.3% of patients who underwent iodine 125 plaque brachytherapy. More recent studies revealed local recurrence rates of 4-15% at 5 years dependent on various factors (T-size category according to AJCC, presence of ciliary body involvement or extrascleral extension). These data are important, in that local tumour recurrence is a complication thought to be associated with an increased risk of uveal metastasis and thus decreased survival. Metastatic disease is demonstrated in 28% with local recurrence and the median time from local recurrence to metastasis is 6.8 years. The 5- and 10-year overall survival is 87% and 82% respectively. Based on AJCC staging for posterior uveal melanoma, 10-year metastatic rate is 12% for stage I tumours, 29% for stage II, and 61% for stage III. The risk of metastasis and death increased three-fold with each increasing melanoma staging. Enucleation is required in about 6% of all patients, the majority during the first years. The most common reason for secondary enucleation is tumour regrowth (51% of cases), followed by uncontrollable neovascular glaucoma (31%), scleral melting (7%) painful bullous keratopathy (2%) and painful hemolytic glaucoma (2%) . Management of Recurrences Radiation treatment by plaque brachytherapy has the lowest rate of treatment failures. Iodine-125 and Ruthenium-106 (106Ru) brachytherapy are both associated with a weighted average local recurrence rate of 4-15% and the recent introduction of the intraoperative ultrasound plaque localization during brachytherapy has been shown to further reduce the risk of local treatment failure. Stereotactic radiotherapy has similar rates of 2% charged particle radiation therapy has a lower weighted average rate of local failure at 4.2%. Overall, surgical modalities have a higher rate of local failure compared with radiation modalities (18.6% vs 6.15%). TranspupillaryThermotherapy has the largest reported variation in failure rates from0% to 55.6%, with a weighted average of 20.8%. It is possible to observe different kinds of recurrence and depending of their growth pattern, they may take the form of marginal, central, diffuse or distant recurrence or extrascleral

11. MONITORING

During the treatment time (applicator in place) only general rules of radioprotection have to be taken into consideration. For the beta emitter Ruthenium-106, the electrons are almost completely absorbed within the eye ball.There is an extremely small amount of bremsstrahlung background near the patient, which usually can be ignored. Each person in contact with such patient has to be allowed to come into contact with radiation and should be monitored for radiation protection based on the internal institutional policy and according to national radiation protection rules. For iodine-125, the low energy photons are not completely absorbed within the eye ball. Half value layers in water (or tissue) for Iodine-125 and Pd-103 are less than 2 cm. The half value layer for 125 I in lead is 0.025 mm, hence common lead shielding provides sufficient protection. However, for eye plaque brachytherapy the general radiation protection rules should always be taken into consideration for those frequently handling applicators: minimizing exposure time for personal and patient, maximizing distance (e.g. by using forceps) and using protection where possible (e.g. by wearing lead aprons). Specific acute side effects like swelling of the conjunctiva and acute exudative retinal detachment are transient and require symptomatic treatment only. Prophylactic systemic treatment with oral non-steroidal anti- inflammatory drugs may be indicated, while local treatment after surgery includes atropine and anti-inflammatory medications, in combination with a local antibiotic. After brachytherapy, patients are followed for local control, complications, and systemic disease every 3-6 months. Patients with posteriorly located tumours are at higher risk of radiation maculopathy and radiation optic neuropathy, and visual acuity is checked at each visit. These effects typically occur gradually within the first 3 years of follow-up. Similarly, most local tumour recurrence occurs during the first 5 years. In addition, patients should be periodically reexamined for evidence of metastatic disease. Imaging studies of the liver and biochemical tests of liver function are necessary as the baseline work up.

12. RESULTS

Treatment results and morbidity are specific for the different isotopes ruthenium-106 and iodine-125.