Sabine Delacroix

Treatment of Uveal Melanoma by Accelerated Proton Beam

Proton beam irradiation of uveal melanoma has great advantages compared to brachytherapy because of the homogenous dose delivered to the tumor and the possibility of sparing normal tissue close to the tumor. We describe the technique of proton beam therapy including the surgical technique of clip positioning, the radiotherapy delivery technique and the dose administered (60 Gy cobalt relative biological effectiveness in 4 fractions). Indications of proton beam are given and the follow-up procedure is described. An inactive residual tumor scar is observed after 2-3 years. Results are given comparing the most recent series of patients treated at the Institut Curie-Orsay proton therapy center with the data published in the literature. The metastasis rate at 10 years varies between 25 and 30%. Local control is excellent. The local recurrence rate at 10 years is usually around 5%. Secondary enucleation is performed in 10-15% of patients either due to complications or local recurrence. Complications such as retinal detachment, maculopathy, papillopathy, cataract, glaucoma, vitreous hemorrhage and dryness are described. The severest complication that usually leads to secondary enucleation is neovascular glaucoma and it is encountered after irradiation of large to extra-large tumors. The toxic tumor syndrome has recently been described. It is hypothesized that the residual tumor scar may produce proinflammatory cytokines and VEGF leading to intraocular inflammation and neovascular glaucoma. Additional treatments after proton beam such as transpupillary thermotherapy, endoresection of the tumor scar or intravitreal injections of anti-VEGF may reduce the rate of these complications.

Combined Proton Beam Radiotherapy and Transpupillary Thermotherapy for Large Uveal Melanomas: A Randomized Study of 151 Patients

Introduction: Exudation from the tumour scar and glaucoma can be major problems after proton beam irradiation of uveal melanoma and can sometimes lead to secondary enucleation. We conducted a randomized study to determine whether systematic transpupillary thermotherapy (TTT) after proton beam radiotherapy could have a beneficial effect. Patients and Method:Between February 1999 and April 2003, all the patients treated by proton beam radiotherapy for uveal melanomas ≧7 mm thick or ≧15 mm in diameter were included in this study after giving their informed consent. One half of the patients received proton beam radiotherapy alone (60 Gy in 4 fractions) and the other half received the same dose of proton beam radiotherapy followed by TTT at 1, 6 and 12 months. All the information concerning the initial tumour parameters, treatments and follow-up was recorded and a statistical analysis was performed. Results: We randomized 151 patients. The median follow-up was 38 months. The 2 groups of patients were similar in terms of age, gender and tumour characteristics. The patients treated with TTT showed a greater reduction of tumour thickness (p = 0.06), less retinal detachment at the latest follow-up (p = 0.14) and a lower secondary enucleation rate (p = 0.02). Discussion: The present study is the first randomized analysis to demonstrate a significant decrease in the secondary enucleation rate in patients treated with TTT after proton beam radiotherapy. Further studies should be performed to determine whether TTT could be beneficial to smaller tumours and to define its optimal dose.

Proton beam therapy for iris melanomas

AimsTo describe the results in terms of local control, eye preservation and systemic evolution of iris melanomas treated by proton beam irradiation.MethodsRetrospective review of the charts of patients with iris melanoma treated by proton beam therapy between April 1998 and September 2002. Ciliary body melanomas with iris involvement or tumours with extrascleral invasion were excluded. Treatment consisted of 60 Gy of proton beam irradiation delivered in four fractions to the tumour volume.ResultsA total of 21 patients were treated, median follow-up of 33 months (8–72 months). 15 patients presented a lesion with documented growth. The median clinical diameter was 5 mm (2–8 mm), the median ultrasound diameter 4.8 mm (2–7.7 mm) The patients were 6% T1, 57.1% T2, and 14.3% T3 all N0M0. The iridocorneal angle was invaded by the tumour in 71.4% of patients. At the end of follow-up, all patients were alive with no proven metastatic disease except one patient with suspicious liver lesions. None of the patients showed tumour progression or ocular relapse. The tumour response at 2 years was a flat lesion for 6.3% of cases, partial regression in 75% and stable in 18.8%. None of the patients required secondary enucleation. The main complication was cataract (45% within 24 months of treatment). Raised intraocular pressure was observed in 15% of patients but no neovascular glaucoma.ConclusionsProton beam therapy shows potential utility for selected cases of localised iris melanomas allowing excellent local tumour control and eye preservation. Further follow-up on larger series is needed to confirm these results.

Long-term results of low-dose proton beam therapy for circumscribed choroidal hemangiomas.

Purpose: To evaluate the long-term efficacy and outcome of low-dose proton beam irradiation in the treatment of symptomatic circumscribed choroidal hemangioma. Patients and Methods: Retrospective review of 71 patients with symptomatic circumscribed choroidal hemangiomas treated by proton beam irradiation between September 1994 and October 2002 using a total dose of 20 Cobalt Gray Equivalent. Results: The median follow-up was 52 months (8–133 months). Retinal reattachment was obtained in all cases. Tumor thickness decreased in all cases and a completely flat scar was obtained in 65 patients (91.5%). Visual acuity was improved by two lines or more in 37 of the 71 patients (52%), and in 30 of the 40 patients (75%) treated within 6 months after onset of the first symptoms. The main radiation complications detected during follow-up were cataract (28%) and radiation-induced maculopathy (8%). None of the 71 patients developed eyelid sequelae or neovascular glaucoma. Conclusion: Proton beam irradiation with a total dose of 20 Cobalt Gray Equivalent appears to be a valid treatment for circumscribed choroidal hemangiomas, inducing definitive retinal reattachment and decreasing tumor thickness. However, delayed radiation-induced maculopathy may occur. A successful functional outcome is dependent on a short interval between onset of the first symptoms and initiation of therapy.

Intraocular inflammation after proton beam irradiation for uveal melanoma

AIM To describe the inflammatory reaction that can occur following proton beam irradiation of uveal melanomas based on a large series of patients and to try to determine the risk factors for this reaction. METHODS Data from a cohort of patients with uveal melanoma treated by proton beam irradiation between 1991 and 1994 were analysed. The presence of inflammation was recorded and evaluated. Kaplan-Meier estimates and statistical analysis of general and tumour related risk factors were performed. RESULTS 28% of patients treated during this period presented with ocular inflammation (median follow up 62 months). Risks factors were essentially tumour related and were correlated with larger lesions (height > 5 mm, diameter > 12 mm, volume > 0.4 cm3). Multivariate analysis identified initial tumour height and irradiation of a large volume of the eye as the two most important risk factors. Ocular inflammation usually consisted of mild anterior uveitis, resolving rapidly after topical steroids and cycloplegics. The incidence of inflammation after proton beam irradiation of melanomas seems higher than previously reported and is related to larger lesions. Evidence of inflammation associated with uveal melanoma has been described and seems to be associated with tumour necrosis (spontaneous or after irradiation). The appearance of transient inflammation during the follow up of these patients may be related to the release of inflammatory cytokines during tumour necrosis. CONCLUSION Inflammation following proton beam irradiation is not unusual. It is correlated with larger initial tumours and may be related to tumour necrosis.

Proton dosimetry comparison involving ionometry and calorimetry

A comparison of the absorbed dose to tissue determined by various ionization chambers, Faraday cups, and an A-150 plastic calorimeter was performed in the 200 MeV proton beam of Orsay, France. Four European proton-therapy centers (Clatterbridge, UK, Louvain la Neuve, Belgium, and Nice and Orsay, France) participated in the comparison. An agreement of better than 1% was observed in the absorbed dose to A-150 measured with the different chambers of the participating groups. The mean ratio of the absorbed dose to A-150 determined with the calorimeter to that determined by the different ionization chambers in the different irradiation conditions was found to be 0.952 +/- 0.007 [1 standard deviation (SD)] according to the code of practice used by all the participating centers, based on Jannis tables of stopping powers and a value of 35.2 J/Coulomb for (W(air)/e)p. A better agreement in the mean ratio calorimeter/chamber, 0.985 +/- 0.007 (1 SD) is observed when using the proton stopping power ratio values recently published by the International Commission on Radiation Units and Measurements in Report no. 49. The mean ratio of these doses determined in accordance with the American Association of Physicists in Medicine protocol and using the new recommended stopping power tables becomes 1.002 +/- 0.007 (1 SD). Two Faraday cups agree in measured charge to within 0.8%; however, the calculation of dose is underestimated by up to 17%; compared with ion chamber measurements and seems to be very sensitive to measurement conditions, particularly to the distance to the collimator.

Configuration and validation of an analytical model predicting secondary neutron radiation in proton therapy using Monte Carlo simulations and experimental measurements

PURPOSE This study focuses on the configuration and validation of an analytical model predicting leakage neutron doses in proton therapy. METHODS Using Monte Carlo (MC) calculations, a facility-specific analytical model was built to reproduce out-of-field neutron doses while separately accounting for the contribution of intra-nuclear cascade, evaporation, epithermal and thermal neutrons. This model was first trained to reproduce in-water neutron absorbed doses and in-air neutron ambient dose equivalents, H*(10), calculated using MCNPX. Its capacity in predicting out-of-field doses at any position not involved in the training phase was also checked. The model was next expanded to enable a full 3D mapping of H*(10) inside the treatment room, tested in a clinically relevant configuration and finally consolidated with experimental measurements. RESULTS Following the literature approach, the work first proved that it is possible to build a facility-specific analytical model that efficiently reproduces in-water neutron doses and in-air H*(10) values with a maximum difference less than 25%. In addition, the analytical model succeeded in predicting out-of-field neutron doses in the lateral and vertical direction. Testing the analytical model in clinical configurations proved the need to separate the contribution of internal and external neutrons. The impact of modulation width on stray neutrons was found to be easily adjustable while beam collimation remains a challenging issue. Finally, the model performance agreed with experimental measurements with satisfactory results considering measurement and simulation uncertainties. CONCLUSION Analytical models represent a promising solution that substitutes for time-consuming MC calculations when assessing doses to healthy organs.

La protonthérapie : bases, indications et nouvelles technologies

With over 70,000 patients treated worldwide, protontherapy has an evolution on their clinical applications and technological developments. The ballistic advantage of the Bragg peak gives the possibility of getting a high conformation of the dose distribution to the target volume. Protontherapy has accumulated a considerable experience in the management of selected rare malignancies such as uveal melanomas and base of the skull chordomas and chondrosarcomas. The growing interest for exploring new and more common conditions, such as prostate, lung, liver, ENT, breast carcinomas, as well as the implementation of large pediatric programs advocated by many experts has been challenged up to now by the limited access to operational proton facilities, and by the relatively slow pace of technical developments in terms of ion production, beam shaping and modelling, on-line verification etc. One challenge today is to deliver dynamic techniques with intensity modulation in clinical facilities as a standard treatment. We concentrate in this paper on the evolution of clinical indications as well as the potentialities of new technological concepts on ion production, such as dielectric walls and laser-plasma interactions. While these concepts could sooner or later translate into prototypes of highly compact equipments that would make easier the implantation of cost-effective hospital-based facilities, the feasibility of their clinical use must still be proved.

An experimental approach to the design of a scattering system for a proton therapy beam line dedicated to opthalmological applications

PURPOSE The development of a scattering system for a proton therapy beam line dedicated to ophthalmological applications. METHODS AND MATERIALS A protontherapy beam line has been developed for the treatment of uveal melanoma at the Orsay synchrocyclotron. The original 200 MeV proton beam is degraded to 76 MeV and the final beam characteristics (range, modulation, flatness, collimation) are obtained with beam modifiers in the treatment room. A passive scattering system is used to obtain a uniform dose distribution in the beam cross-section throughout 30 mm in diameter, with minimal losses in energy and dose rate. We have used an experimental approach for the scattering study. RESULTS An elliptical ring shaped from 0.1-mm thick lead is the solution we have adopted for the scattering system. For a modulated beam, a flatness of 1% is obtained on transverse profiles. The energy loss introduced by this scatterer is only 0.5 MeV, with no appreciable change in the range over the treatment field. For an unmodulated beam, 21% of intensity is lost when the scatterer is used. The distal and the lateral dose fall-off (90-10%) for a modulated beam are 2.6 mm. These last values are independent of the range and the modulation currently used for the ophthalmic applications. CONCLUSION A specific passive scattering system can be adapted to a particular beam emittance. A systematic experimental approach can easily be undertaken to obtain the scatterer adapted for small irradiation fields in proton therapy.

Évolution des indications cliniques en hadronthérapie 2008–2012

Hadrontherapy, a type of radiation therapy dealing with heavy charged particles, has become for the past decade one of the most sophisticated and attractive approach in the management of cancer. This is related with major technological innovations that have made available, at a relatively cheap cost, compact proton accelerators equipped with rotational gantries. The implementation of pencil beam scanning should also make treatment planning and delivery much easier and faster than conventional approaches. Until now, approximately 100,000 patients have been treated with protons worldwide. Due to more complex technological and biological challenges, light ion therapy - mainly carbon ions - has developed at a lower pace, except in Japan where most of the 15,000 treated patients have been enrolled. Current indications for protons include firstly, locally aggressive tumours non or incompletely resected, that are located close to critical normal structures: ocular melanomas, skull base and spinal canal low grade sarcomas, selected ENT carcinomas (like adenoid cystic); secondly, improvement of tolerance to radiations: delayed, mainly in paediatric malignancies, due to the exquisite sensitivity of organs under development (including to carcinogenesis); immediate, on bone marrow, mucosae… mainly in concomitant radiation-chemotherapy interactions (tested in esophagus, and lung). Most promising indications for carbon ions include inoperable highly radioresistant primaries, such as mucosal melanomas, high grade bone and soft part sarcomas, and pancreatic carcinomas. Altered fractionations are also of interests that could translate in clinical and economical benefits. Controversies have risen whether more common indications, like prostate, should also be explored.