Study Assessing Two Models of Hypofractionated Protontherapy on Large Choroidal Melanomas

Overview

Ocular melanomas have been treated for a long time by enucleation, with an unfavorable major impact on the patient's quality of life, social life, self-image, how they feel about others and about living with this disability. As a matter of fact, classical radiation therapy by photons is not accurate enough to deliver a sufficiently high dose to eradicate a melanoma without causing irreversible ocular brain complications since these tumors are " relatively radio resistant ". The possibility of delivering high doses due to the precision of protons ("Bragg peak") has allowed to overcome this limitation. The conservative uveal melanoma treatment has become a standard after the Collaborative Ocular Melanoma Study (COMS) indicating an equivalent rate of metastases and a non-impaired survival rate with a conservative treatment when compared to immediate enucleation. The quality of life benefits due to a conservative treatment has been demonstrated. Protontherapy dose has been defined in an empirical manner, it is probably excessive even if it applies to radio-resistant tumors. In France, radiotherapy by protons for choroidal melanomas delivers a dose of 60 Gy cobalt equivalent (that is 52 measured Gy, or " Physical dose") in 4 fractions and 4 days. Referential treatment of ocular melanomas (other than conjunctiva) indicates proton-therapy for T1, T2, T3 \< 40% of ocular volume, and T4 only if extra scleral extension ≤ 2mm. However, there is an enucleation indication for T3 \> 40% of ocular volume and T4. Our purpose is to override this relative contraindication, choroidal melanoma volume ≥ 40% of ocular volume. As a matter of fact, the investigators observe an increasing demand from ophthalmologists and patients for not performing primary enucleation. Also, during the last five years treatment of complications have improved and a less " hard " hypo fractionation (6.5 Gy per fraction) has equivalent local control results as for " hard " fractionation (13 Gy per fraction).

A more fractioned proton-therapy treatment, with doses per fraction of 6.5 Gy rather than 13 Gy, can limit the rate and the severity of complications degrading the quality of life by complications (pain, diminished visual acuity) and treatments (intra-ocular injections...). In this study, patients will receive a total dose of 52 Gy in four 13 Gy sessions for the standard arm and in eight 6.5 Gy sessions for the experimental arm. The investigators expect an identical local control rate within 2 year's time with a decrease in rate and severity of severe complications due to adapted fractionation (eight sessions with lower doses instead of four fractions with very high doses as it is usually recommended in the guidelines for small to medium melanomas).