Eye retention after proton beam radiotherapy for uveal melanoma

Radiotherapy for ocular tumours

Ocular tumours present a therapeutic challenge because of the sensitive tissues involved and the necessity to destroy the tumour while minimising visual loss. Radiotherapy (RT) is one of several modalites used apart from surgery, laser, cryotherapy, and chemotherapy. Both external beam RT (EBRT) and brachytherapy are used. Tumours of the bulbar conjunctiva, squamous carcinoma and malignant melanoma, can be treated with a radioactive plaque: strontium-90, ruthenium-106 (Ru-106), or iodine-125 (I-125), after excision. If the tumour involves the fornix or tarsal conjunctiva, proton therapy can treat the conjunctiva and spare most of the eye. Alternatively, an I-125 interstitial implant can be used with shielding of the cornea and lens. Conjunctival mucosal-associated lymphoid tissue lymphoma can be treated with an anterior electron field with lens shielding and 25-30 Gray (Gy) in 2 Gy fractions. Discrete retinoblastoma (RB), too large for cryotherapy or thermolaser, or recurrent after these modalities, can be treated with plaque therapy, I-125, or Ru-106. For large RB, multiple tumours, or vitreous seeds the whole eye can be treated with an I-125 applicator, sparing the bony orbit, or with EBRT, under anaesthetic, using X-rays or proton therapy with vacuum contact lenses to fix the eyes in the required position. Post-enucleated orbits at risk for recurrent RB can be treated with an I-125 implant with shielding to reduce the dose to the bony orbit. Uveal malignant melanomas can be treated with plaque or proton therapy with excellent local control. Preservation of vision will depend on the initial size and location of the tumour.

Eye tracking and gating system for proton therapy of orbital tumors

PURPOSE

A new motion-based gated proton therapy for the treatment of orbital tumors using real-time eye-tracking system was designed and evaluated.

METHODS

We developed our system by image-pattern matching, using a normalized cross-correlation technique with LabVIEW 8.6 and Vision Assistant 8.6 (National Instruments, Austin, TX). To measure the pixel spacing of an image consistently, four different calibration modes such as the point-detection, the edge-detection, the line-measurement, and the manual measurement mode were suggested and used. After these methods were applied to proton therapy, gating was performed, and radiation dose distributions were evaluated.

RESULTS

Moving phantom verification measurements resulted in errors of less than 0.1 mm for given ranges of translation. Dosimetric evaluation of the beam-gating system versus nongated treatment delivery with a moving phantom shows that while there was only 0.83 mm growth in lateral penumbra for gated radiotherapy, there was 4.95 mm growth in lateral penumbra in case of nongated exposure. The analysis from clinical results suggests that the average of eye movements depends distinctively on each patient by showing 0.44 mm, 0.45 mm, and 0.86 mm for three patients, respectively.

CONCLUSIONS

The developed automatic eye-tracking based beam-gating system enabled us to perform high-precision proton radiotherapy of orbital tumors.

Differences in uveal melanomas between men and women from the British Isles

PURPOSE

The purpose of this study is to compare uveal melanomas (UMs) in men and women.

METHODS

The Liverpool Ocular Oncology Centre (LOOC) database was reviewed. Patients treated for UM at the LOOC between 1993 and 2010 were selected. Differences between sexes were identified using the χ (2)-test for categorical variables and the Mann-Whitney test for continuous variables.

RESULTS

The 3380 patients comprised 1685 women and 1695 men. The tumours were considered clinically to have arisen in choroid in 89.5%, ciliary body in 5.3%, and iris in 5.2%. Tumours in women were less likely to originate in choroid (87.2 vs 91.7%; P<0.001) and showed more circumferential spread in ciliary body (P<0.001) and iris (P=0.003). Tumours in men were more likely to extend to within 3 mm of optic disc or fovea (46.3 vs 39.0%, P<0.001), showing more extensive optic-disc involvement (P<0.001). The median largest basal tumour diameter was 12.2 mm in men and 11.9 mm in women (P=0.001). The tumour thickness had a median of 4.4 mm and 3.8 mm in men and women, respectively (P=0.015). The 180 ciliary body tumours occurred in 112 women and 68 men. In these, the prevalence of extraocular spread was higher in women (19.6 vs 8.8%; P=0.052). The 175 iris melanomas were more common in women than men (103 vs 72, respectively).

CONCLUSIONS

In men, UMs tend to be larger and more posterior than in women.

Electron beam radiation for conjunctival squamous carcinoma

PURPOSE

To describe the authors' technique and preliminary results using electron beam radiation as rescue therapy for recalcitrant squamous cell carcinoma of the conjunctiva and cornea.

METHODS

A retrospective review comprised of an interventional case series of patients with pathologically confirmed diagnosis of squamous cell carcinoma of the conjunctiva and cornea, who had failed multiple standard treatments and underwent electron beam radiation therapy. Outcomes, radiation-related complications, and adverse effects were documented. Mortality and local control rates were calculated by the Kaplan-Meier survival probability method.

RESULTS

Eight patients met the inclusion criteria; of these, 6 (75%) were men and 2 (25%) were women, with ages ranging from 38 to 65 years (mean 50 years). One tumor (12.5%) was classified as T2N0M0, 6 (75%) were classified as T3N0M0, and one (12.5%) was classified as T4N0M0. Follow up from electron beam radiation therapy ranged from 3 to 72 months (mean 30.25 months). The most common side effect was erythema and edema of the eyelids with diffuse transient eyelash loss, seen in all patients. Tumor local control and regression after electron beam radiation therapy were noted in 6 patients (75%); recurrence was noted in 2. There was neither metastatic spread nor tumor-related deaths.

CONCLUSIONS

The authors report a small case series where local tumor control was achieved with electron beam radiation therapy for recalcitrant squamous cell carcinoma of the conjunctiva and cornea. This approach may be considered for patients who fail conventional therapy.

Response of human HTB140 melanoma cells to conventional radiation and hadrons

Conventional radiotherapy with X- and gamma-rays is one of the common and effective treatments of cancer. High energy hadrons, i.e., charged particles like protons and (12)C ions, due to their specific physics and radiobiological advantages are increasingly used. In this study, effectiveness of different radiation types is evaluated on the radio-resistant human HTB140 melanoma cells. The cells were irradiated with gamma-rays, the 62 MeV protons at the Bragg peak and in the middle of the spread-out Bragg peak (SOBP), as well as with the 62 MeV/u (12)C ions. The doses ranged from 2 to 24 Gy. Cell survival and proliferation were assessed 7 days after irradiation, whereas apoptosis was evaluated after 48 h. The acquired results confirmed the high radio-resistance of cells, showing better effectiveness of protons than gamma-rays. The best efficiency was obtained with (12)C ions due to higher linear energy transfer. All analyzed radiation qualities reduced cell proliferation. The highest proliferation was detected for (12)C ions because of their large killing capacity followed by small induction of reparable lesions. This enabled unharmed cells to preserve proliferative activity. Irradiations with protons and (12)C ions revealed similar moderate pro-apoptotic ability that is in agreement with the level of cellular radio-resistance.

Proton radiation therapy offers reduced normal lung and bone marrow exposure for patients receiving dose-escalated radiation therapy for unresectable stage iii non-small-cell lung cancer: a dosimetric study

INTRODUCTION

The purpose of this study was to determine the potential benefit of proton radiation therapy over photon radiation therapy in patients with unresectable stage III non-small-cell lung cancer.

MATERIALS AND METHODS

Optimized 3-dimensional conformal photon (3DCRT), intensity-modulated radiation therapy (IMRT) and proton therapy (PT) plans were generated for 8 consecutive patients with unresectable stage III non-small-cell lung cancer using the same target goals and normal tissue constraints. The radiation exposure to non-targeted normal structures, including lung, bone marrow, esophagus, heart, and spinal cord, were compared. Photon doses are expressed in gray (Gy). Proton doses are expressed in cobalt gray equivalents (CGE).

RESULTS

In all patients, 3DCRT, IMRT, and PT plans, achieved the dose goals for the target volumes. Compared with the 3DCRT plans, proton plans offered a median 29% reduction in normal lung V(20) Gy (CGE), a median 33% reduction in mean lung dose (MLD), and a median 30% reduction in the volume of bone marrow receiving a dose of 10 Gy (CGE). Compared with the IMRT plans, the proton plans offered a median 26% reduction in normal lung V(20) Gy (CGE), a median 31% reduction in MLD, and a median 27% reduction in the volume of bone marrow receiving a dose of 10 Gy (CGE).

CONCLUSION

By reducing the volumes of normal structures irradiated, protons can potentially improve the therapeutic index for patients with unresectable stage III non-small-cell lung cancer receiving combined radiation therapy and chemotherapy.

Review of clinical experience with ion beam radiotherapy

The article describes both the early development of oncology as a core discipline at the University of Heidelberg Hospital and the first steps towards ion beam treatment, from the pilot project carried out in co-operation with the Gesellschaft für Schwerionenforschung Darmstadt to the initial start-up of clinical service at the Heidelberg Heavy Ion Centre (HIT). We present an overview, based on data published in the literature, of the available clinical evidence relating the use of ion beam therapy to treat major indications in active particle centres. A rationale for the use of particle therapy in each of these indications is given. In view of the limited availability of data, we discuss the necessity to conduct clinical trials. We also look forward towards the next activities to be undertaken at the HIT.

Ocular Melanoma and Other Unusual Sites

Noncutaneous melanoma is a rare entity for which there is still no agreement about management. The rarity of this disease has resulted in a lack of significant investigation and insufficient opportunity to evaluate the epidemiologic features, risk factors, and the most useful diagnostic and therapeutic approaches. Noncutaneous melanomas are characterized by poor prognosis, and the diagnosis is usually delayed because of their unusual locations and lack of physician awareness. This review focuses principally on ocular melanoma, the most frequent noncutaneous melanoma, for which each aspect of the disease is described. The potential utility of nuclear medicine procedures is also considered.

The clinical experience with particle therapy in adults

Radiation therapy with charged particles, such as protons and heavier ions, provides physical selectivity and therefore allows for favorable dose distributions in comparison with conventional photon radiotherapy. Carbon ions furthermore exhibit biologic advantages related to their high linear energy transfer properties in a number of tumors known to be relatively insensitive to low-linear energy transfer radiation therapy. Over the last 2 decades, major developments in the fields of accelerator technology, diagnostic techniques, and beam delivery methods have been made. These developments formed the basis for the application of particle beams in clinical surroundings. Many clinical centers are already considering the introduction of radiation therapy with charged particles. This article reviews the clinical experience with particle therapy in adults available so far.

Local tumor control, visual acuity, and survival after hypofractionated stereotactic photon radiotherapy of choroidal melanoma in 212 patients treated between 1997 and 2007

PURPOSE

To evaluate long-term local tumor control, visual acuity, and survival after hypofractionated linear accelerator-based stereotactic photon radiotherapy in patients with choroidal melanoma.

METHODS AND MATERIALS

Between 1997 and 2007, 212 patients with choroidal melanoma unsuitable for ruthenium-106 brachytherapy or local resection were treated stereotactically at a linear accelerator with 6-MV photon beams at the Medical University of Vienna in five fractions over 7 days. Twenty-four patients received a total dose of 70 Gy (five fractions of 14 Gy), 158 a total dose of 60 Gy (five fractions of 12 Gy) and 30 patients a total dose of 50 Gy (five fractions of 10 Gy) applied on the 80% isodose. Ophthalmologic examinations were performed at baseline and every 3 months in the first 2 years, every 6 months until 5 years, and once a year thereafter until 10 years after radiotherapy. Assessment of visual acuity, routine ophthalmologic examinations, and measurement of tumor base dimension and height using standardized A-scan and B-scan echography were done at each visit. Funduscopy and fluorescein angiography were done when necessary to document tumor response.

RESULTS

Median tumor height and volume decreased from 4.8 mm and 270.7 mm3 at baseline to 2.6 mm and 86.6 mm3 at the last individual follow-up, respectively (p<0.001, p<0.001). Median visual acuity decreased from 0.55 at baseline to hand motion at the last individual follow-up (p<0.001). Local tumor control was 95.9% after 5 years and 92.6% after 10 years. Thirty-two patients developed metastatic disease, and 22 of these patients died during the follow-up period.

CONCLUSION

Hypofractionated stereotactic photon radiotherapy with 70 to 50 Gy delivered in five fractions in 7 days is sufficient to achieve excellent local tumor control in patients with malignant melanoma of the choroid. Disease outcome and vision are comparable to those achieved with proton beam radiotherapy. Decreasing the total dose below 60 Gy seems to be possible.

Proton-beam therapy for tumors of the CNS

The focus of this review is proton radiotherapy for primary neoplasms of the brain. Although glial cells are among the most radioresistant in the body, the presence of sensitive critical structures and the high doses needed to control CNS tumors present a formidable challenge to the treating radiation oncologist. Treatment with conventional photon radiation at doses required to control disease progression all too often results in unacceptable toxicity. Protons have intrinsic properties that often allow radiation oncologists to deliver a higher dose to the tumor compared with photons, while at the same time offering better sparing of normal tissues. Recognition of these advantages has resulted in development of many new proton treatment facilities worldwide.

Comparing plaque brachytherapy and proton therapy for choroidal melanoma: a review of the literature

The aims of conservative treatment in patients with ocular melanoma are globe retention, good visual acuity (VA) and local control. Two well-established radiation conservative treatment options are proton beam radiotherapy and episcleral plaque brachytherapy (EPB). Patients who receive treatment with either of these options will experience some degree of radiation-related ocular complications and poor VA. The purpose of this review of the literature is to establish whether there is a significant clinical difference in normal tissue morbidity and local tumour control between proton therapy and EPB, and whether this difference can justify the purchase and implementation of additional proton therapy facilities. Based on this review, evidence suggested that both treatment options are comparable, and that neither proton therapy nor EPB is clinically superior than the other regarding normal tissue morbidity and local tumour control. This review highlighted the need for further research on a larger scale in order to bridge the gap that is apparent within the literature.

The M. D. Anderson proton therapy system

PURPOSE

The purpose of this study is to describe the University of Texas M. D. Anderson proton therapy system (PTC-H) including the accelerator, beam transport, and treatment delivery systems, the functionality and clinical parameters for passive scattering and pencil beam scanning treatment modes, and the results of acceptance tests.

METHODS

The PTC-H has a synchrotron (70-250 MeV) and four treatment rooms. An overall control system manages the treatment, physics, and service modes of operation. An independent safety system ensures the safety of patients, staff, and equipment. Three treatment rooms have isocentric gantries and one room has two fixed horizontal beamlines, which include a large-field treatment nozzle, used primarily for prostate treatments, and a small-field treatment nozzle for ocular treatments. Two gantry treatment rooms and the fixed-beam treatment room have passive scattering nozzles. The third gantry has a pencil beam scanning nozzle for the delivery of intensity modulated proton treatments (IMPT) and single field uniform dose (SFUD) treatments. The PTC-H also has an experimental room with a fixed horizontal beamline and a passive scattering nozzle. The equipment described above was provided by Hitachi, Ltd. Treatment planning is performed using the Eclipse system from Varian Medical Systems and data management is handled by the MOSAIQ system from IMPAC Medical Systems, Inc. The large-field passive scattering nozzles use double scattering systems in which the first scatterers are physically integrated with the range modulation wheels. The proton beam is gated on the rotating range modulation wheels at gating angles designed to produce spread-out-Bragg peaks ranging in size from 2 to 16 g/cm2. Field sizes of up to 25 x 25 cm2 can be achieved with the double scattering system. The IMPT delivery technique is discrete spot scanning, which has a maximum field size of 30 x 30 cm2. Depth scanning is achieved by changing the energy extracted from the synchrotron (energy can be changed pulse to pulse). The PTC-H is fully integrated with DICOM-RT ION interfaces for imaging, treatment planning, data management, and treatment control functions.

RESULTS

The proton therapy system passed all acceptance tests for both passive scattering and pencil beam scanning. Treatments with passive scattering began in May 2006 and treatments with the scanning system began in May 2008. The PTC-H was the first commercial system to demonstrate capabilities for IMPT treatments and the first in the United States to treat using SFUD techniques. The facility has been in clinical operation since May 2006 with up-time of approximately 98%.

CONCLUSIONS

As with most projects for which a considerable amount of new technology is developed and which have duration spanning several years, at project completion it was determined that several upgrades would improve the overall system performance. Some possible upgrades are discussed. Overall, the system has been very robust, accurate, reproducible, and reliable. The authors found the pencil beam scanning system to be particularly satisfactory; prostate treatments can be delivered on the scanning nozzle in less time than is required on the passive scattering nozzle.

Number of patients potentially eligible for proton therapy

A group of Swedish radiation oncologists and hospital physicists have estimated the number of patients in Sweden suitable for proton beam therapy in a facility where one of the principal aims is to facilitate randomized and other studies in which the advantage of protons can be shown and the magnitude of the differences compared with optimally administered conventional radiation treatment, also including intensity-modulated radiation therapy (IMRT) and brachytherapy, can be shown. The estimations have been based on current statistics of tumour incidence in Sweden, number of patients potentially eligible for radiation treatment, scientific support from clinical trials and model dose planning studies and knowledge of the dose-response relations of different tumours together with information on normal tissue complication rates. In Sweden, it is assessed that between 2200 and 2500 patients annually are eligible for proton beam therapy, and that for these patients the potential therapeutic benefit is so great as to justify the additional expense of proton therapy. This constitutes between 14-15% of all irradiated patients annually.

The potential of proton beam radiation therapy in intracranial and ocular tumours

A group of oncologists and hospital physicists have estimated the number of patients in Sweden suitable for proton beam therapy. The estimations have been based on current statistics of tumour incidence, number of patients potentially eligible for radiation treatment, scientific support from clinical trials and model dose planning studies and knowledge of the dose-response relations of different tumours and normal tissues. In intracranial benign and malignant tumours, it is estimated that between 130 and 180 patients each year are candidates for proton beam therapy. Of these, between 50 and 75 patients have malignant glioma, 30-40 meningeoma, 20-25 arteriovenous malformations, 20-25 skull base tumours and 10-15 pituitary adenoma. In addition, 15 patients with ocular melanoma are candidates.

Radiobiological analysis of human melanoma cells on the 62 MeV CATANA proton beam

PURPOSE

To measure the ability of protons and gamma-rays to effect cell viability and cell survival of human HTB140 melanoma cells.

MATERIALS AND METHODS

Exponentially growing HTB140 cells were irradiated close to the Bragg peak maximum of the 62 MeV protons or with 60Co gamma-rays with single doses, ranging from 8 - 24 Gy. Cell viability using the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay was evaluated at 6 h, 24 h, 48 h or 7 days after irradiation and clonogenic survival was assessed at 7 days after irradiation. Cell cycle phase redistribution and the level of apoptosis were evaluated at 6 h and 48 h after irradiation.

RESULTS

The study of cell viability as a function of time (cell survival progression) and cell survival, using a clonal assay, demonstrated the considerably stronger inactivation effect of protons compared to gamma-rays with a relative biological effectiveness (RBE) of approximately 1.64. Cell cycle phase distribution and apoptosis levels with time enabled us to investigate the development and the character of the damage induced by irradiation. Due to the high radio-resistance of HTB140 cells, cell cycle phase redistribution exhibited only a modest cell accumulation in G2/M phase. Protons but not gamma-rays induced apoptosis.

CONCLUSIONS

It appears that protons reduce the number of HTB140 cells by apoptosis as well as by severe DNA damage, while gamma-rays eliminate viable cells primarily by the production of irreparable DNA damage. Protons have an increased RBE relative to gamma-rays.

The effectiveness and safety of proton radiation therapy for indications of the eye : a systematic review

BACKGROUND AND PURPOSE

: Proton radiation has been used for the treatment of uveal melanoma since 1975, but few studies have been conducted to assess its efficacy and safety. This paper aims to systematically review the effects and side effects of proton therapy for any indication of the eye.

MATERIAL AND METHODS

: A range of databases were searched from inception to 2007. All studies that included at least ten patients and that assessed the efficacy or safety of proton therapy for any indication of the eye were included.

RESULTS

: The search generated 2,385 references, of which 37 met the inclusion criteria. Five controlled trials, two comparative studies and 30 case series were found, most often reporting on uveal melanoma, choroidal melanoma and age-related macular degeneration (AMD). Methodological quality of these studies was poor. Studies were characterized by large differences in radiation techniques applied within the studies, and by variation in patient characteristics within and between studies. Results for uveal melanoma and choroidal melanoma suggest favorable survival, with, however, significant rates of side effects. Results for choroidal hemangioma and AMD did not reveal beneficial effects from proton radiation.

CONCLUSION

: There is limited evidence on the effectiveness and safety of proton radiation due to the lack of well-designed and well-reported studies. There is a need to lift evidence on proton therapy to a higher level by performing dose-finding randomized controlled trials (RCTs), comparative studies of proton radiation versus standard given alternatives and prospective case studies enrolling only patients treated with up-to-date techniques, allowing extrapolation of results to similar patient groups.

Adjuvant intra-arterial hepatic fotemustine for high-risk uveal melanoma patients

Uveal melanoma metastases occur most commonly in the liver. Given the 50% mortality rate in patients at high risk of developing liver metastases, we tested an adjuvant intra-arterial hepatic (i.a.h.) chemotherapy with fotemustine after proton beam irradiation of the primary tumour. We treated 22 high-risk patients with adjuvant i.a.h. fotemustine. Planned treatment duration was 6 months, starting with four weekly doses of 100 mg/m(2), and after a 5-week rest, repeated every 3 weeks. The survival of this patient group was compared with that of a 3 : 1 matched control group randomly selected from our institutional database. Half of the patients experienced > or =grade 3 hepatotoxicity (one patient developing cholangitis 8 years later). Catheter-related complications occurred in 18%. With a median follow-up of 4.6 years for the fotemustine group and 8.5 years for the control group, median overall survival was 9 years [95% confidence interval (CI) 2.2-12.7] and 7.4 years (95% CI 5.4-12.7; P=0.5), respectively, with 5-year survival rates of 75 and 56%. Treatment with adjuvant i.a.h. fotemustine is feasible. However, toxicities are important. Although our data suggest a survival benefit, it was not statistically significant. Confirming such a benefit would require a large, internationally coordinated, prospective randomized trial.

Monte Carlo calculations and measurements of absorbed dose per monitor unit for the treatment of uveal melanoma with proton therapy

The treatment of uveal melanoma with proton radiotherapy has provided excellent clinical outcomes. However, contemporary treatment planning systems use simplistic dose algorithms that limit the accuracy of relative dose distributions. Further, absolute predictions of absorbed dose per monitor unit are not yet available in these systems. The purpose of this study was to determine if Monte Carlo methods could predict dose per monitor unit (D/MU) value at the center of a proton spread-out Bragg peak (SOBP) to within 1% on measured values for a variety of treatment fields relevant to ocular proton therapy. The MCNPX Monte Carlo transport code, in combination with realistic models for the ocular beam delivery apparatus and a water phantom, was used to calculate dose distributions and D/MU values, which were verified by the measurements. Measured proton beam data included central-axis depth dose profiles, relative cross-field profiles and absolute D/MU measurements under several combinations of beam penetration ranges and range-modulation widths. The Monte Carlo method predicted D/MU values that agreed with measurement to within 1% and dose profiles that agreed with measurement to within 3% of peak dose or within 0.5 mm distance-to-agreement. Lastly, a demonstration of the clinical utility of this technique included calculations of dose distributions and D/MU values in a realistic model of the human eye. It is possible to predict D/MU values accurately for clinical relevant range-modulated proton beams for ocular therapy using the Monte Carlo method. It is thus feasible to use the Monte Carlo method as a routine absolute dose algorithm for ocular proton therapy.

Peripheral dose in ocular treatments with CyberKnife and Gamma Knife radiosurgery compared to proton radiotherapy

Peripheral radiation can have deleterious effects on normal tissues throughout the body, including secondary cancer induction and cataractogenesis. The aim of this study is to evaluate the peripheral dose received by various regions of the body after ocular treatment delivered with the Model C Gamma Knife, proton radiotherapy with a dedicated ocular beam employing no passive-scattering system, or a CyberKnife unit before and after supplemental shielding was introduced. TLDs were used for stray gamma and x-ray dosimetry, whereas CR-39 dosimeters were used to measure neutron contamination in the proton experiments. Doses to the contralateral eye, neck, thorax and abdomen were measured on our anthropomorphic phantom for a 56 Gy treatment to a 588 mm(3) posterior ocular lesion. Gamma Knife (without collimator blocking) delivered the highest dose in the contralateral eye, with 402-2380 mSv, as compared with 118-234 mSv for CyberKnife pre-shielding, 46-255 mSv for CyberKnife post-shielding and 9-12 mSv for proton radiotherapy. Gamma Knife and post-shielding CyberKnife delivered comparable doses proximal to the treatment site, with 190 versus 196 mSv at the thyroid, whereas protons doses at these locations were less than 10 mSv. Gamma Knife doses decreased dramatically with distance from the treatment site, delivering only 13 mSv at the lower pelvis, comparable to the proton result of 4 to 7 mSv in this region. In contrast, CyberKnife delivered between 117 and 132 mSv to the lower pelvis. In conclusion, for ocular melanoma treatments, a proton beam employing no double scattering system delivers the lowest peripheral doses proximally to the contralateral eye and thyroid when compared to radiosurgery with the Model C Gamma Knife or CyberKnife. At distal locations in the pelvis, peripheral doses delivered with proton and Gamma Knife are of an order of magnitude smaller than those delivered with CyberKnife.

Dosimetric impact of tantalum markers used in the treatment of uveal melanoma with proton beam therapy

Metallic fiducial markers are frequently implanted in patients prior to external-beam radiation therapy to facilitate tumor localization. There is little information in the literature, however, about the perturbations in proton absorbed-dose distribution these objects cause. The aim of this study was to assess the dosimetric impact of perturbations caused by 2.5 mm diameter by 0.2 mm thick tantalum fiducial markers when used in proton therapy for treating uveal melanoma. Absorbed dose perturbations were measured using radiochromic film and confirmed by Monte Carlo simulations of the experiment. Additional Monte Carlo simulations were performed to study the effects of range modulation and fiducial placement location on the magnitude of the dose shadow for a representative uveal melanoma treatment. The simulations revealed that the fiducials caused perturbations in the absorbed-dose distribution, including absorbed-dose shadows of 22% to 82% in a typical proton beam for treating uveal melanoma, depending on the marker depth and orientation. The clinical implication of this study is that implanted fiducials may, in certain circumstances, cause dose shadows that could lower the tumor dose and theoretically compromise local tumor control. To avoid this situation, fiducials should be positioned laterally or distally with respect to the target volume.

Determination of the dose-depth distribution of proton beam using resazurin assay in vitro and diode laser-induced fluorescence detection

In this study the dose-depth distribution pattern of proton beams was investigated by inactivation of human cells exposed to high-LET (linear energy transfer) protons. The proton beams accelerated up to 45 MeV were horizontally extracted from the cyclotron, and were delivered to the cells acutely through a home made prototype over a range of physical depths (in the form of a variable water column). The biological systems used here were two in vitro cell lines, including human embryonic kidney cells (HEK 293), and human breast adenocarcinoma cell line (MCF-7). Cells were exposed to unmodulated proton beam radiation at a dose of 50 Gy similar to that used in therapy. Resazurin metabolism assay was investigated for measurement of cell response to irradiation as a simple and non-destructive assay. In the resazurin reduction test the non-fluorescent probe dye is reduced to pink and highly fluorescent resorufin. The dose-depth distribution of proton beam obtained based on the highly sensitive laser-induced fluorometric determination of resorufin was found to coincide well with the data collected using conventional film based dosimetry. The resazurin method yielded data comparable with the optical micrographs of the irradiated cells, showing the least cell survival at the measured Bragg-peak position of 10 mm. In addition, fused silica capillary was used as a sample container to increase the probability for irradiated laser beam to probe and excite resorufin in small sample volume of the capillary. The developed method has the potential to serve as a non-destructive, sample-thrifty, and time saving tool to realize more realistic, practical dose-depth distribution of proton beam compared to conventional in vitro cell viability assessment techniques.

A systematic literature review of the clinical and cost-effectiveness of hadron therapy in cancer

BACKGROUND

In view of the continued increase in the number of hadron (i.e. neutron, proton and light or heavy ion) therapy (HT) centres we performed a systematic literature review to identify reports of the efficacy of HT.

METHODS

Eleven databases were searched systematically. No limit was applied to language or study design. Established experts were contacted for unpublished data. Data on outcomes were extracted and summarised in tabular form.

RESULTS

Seven hundred and seventy three papers were identified. For proton and heavy ion therapy, the number of RCTs was too small to draw firm conclusions. Based on prospective and retrospective studies, proton irradiation emerges as the treatment of choice for some ocular and skull base tumours. For prostate cancer, the results were comparable with those from the best photon therapy series. Heavy ion therapy is still in an experimental phase.

CONCLUSION

Existing data do not suggest that the rapid expansion of HT as a major treatment modality would be appropriate. Further research into the clinical and cost-effectiveness of HT is needed. The formation of a European Hadron Therapy Register would offer a straightforward way of accelerating the rate at which we obtain high-quality evidence that could be used in assessing the role of HT in the management of cancer.

Current status of radiotherapy with proton and light ion beams

Several model studies have shown potential clinical advantages with charged particles (protons and light ions) compared with 3D-conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) in many disease sites. The newly developed intensity-modulated proton therapy (IMPT) often yields superior dose distributions to photon IMRT, with the added advantage of a significant reduction in the volume of healthy normal tissues exposed to low-to-medium doses. Initially, the major emphasis in clinical research for proton and light ion therapy was dose escalation for inherently radioresistant tumors, or for lesions adjacent to critical normal structures that constrained the dose that could be safely delivered with conventional x-ray therapy. Since the advent of IMRT the interest in particle therapy has gradually shifted toward protocols aimed at morbidity reduction. Lately the emphasis has mostly been placed on the potential for reduced risk of radiation-induced carcinogenesis with protons. Compared with 3D-CRT, a 2-fold increase has been theoretically estimated with the use of IMRT due to the larger integral volumes. In the pediatric setting, due to a higher inherent susceptibility of tissues, the risk could be significant, and the benefits of protons have been strongly emphasized in the literature. There is a significant expansion of particle therapy facilities around the world. Increasing public awareness of the potential benefits of particle therapy and wider accessibility for patients require that treating physicians stay abreast of the clinical indications of this radiotherapy modality. The article reviews the available literature for various disease sites in which particle therapy has traditionally been considered to offer clinical advantages and to highlight current lines of clinical research. The issue of radiation-induced second malignancies is examined in the light of the controversial epidemiological evidence available. The cost-effectiveness of particle therapy is also discussed.

Particle radiation therapy using proton and heavier ion beams

Particle beams like protons and heavier ions offer improved dose distributions compared with photon (also called x-ray) beams and thus enable dose escalation within the tumor while sparing normal tissues. Although protons have a biologic effectiveness comparable to photons, ions, because they are heavier than protons, provide a higher biologic effectiveness. Recent technologic developments in the fields of accelerator engineering, treatment planning, beam delivery, and tumor visualization have stimulated the process of transferring particle radiation therapy (RT) from physics laboratories to the clinic. This review describes the physical, biologic, and technologic aspects of particle beam therapy. Clinical trials investigating proton and carbon ion RT will be summarized and discussed in the context of their relevance to recent concepts of treatment with RT.

[Results of treating uveal melanoma with proton beam radiation: 10-year follow-up]

PURPOSE

We analyzed the long-term results of uveal melanoma treatment with proton beam irradiation in a series of patients with a follow-up of at least 10 years.

PATIENTS AND METHODS

The patients were treated with proton beam radiation between September 1991 and December 1992. They had an initial examination including visual acuity, funduscopy, A and B scan ultrasonography of the eye, fundus photographs and fluorescein angiography. General examination included chest radiography and B scan ultrasonography of the liver. All tumors received a total dose of 60 cobalt-Gray equivalents (applied in four daily fractions) at the Orsay proton therapy center.

RESULTS

A total of 167 patients were treated with a median follow-up of 116 months. Their median age was 59 years. Thirteen tumors were anterior to the equator, 76 overlapped the equator and 78 were posterior to the equator. An initial retinal detachment was present in 41 cases. The optic disk was invaded in 10 cases. The median tumor diameter was 12 mm and the median tumor thickness was 5.8 mm. The mean initial acuity was 20/50. The survival rate was 62.93% at 10 years; 72.9% of deaths resulted from metastasis. Statistically significant risk factors for death identified in the multivariate analysis were tumor diameter greater than 12 mm (p=0.0004) and age over 60 years (p=0.0001). The metastasis rate at 10 years was 31%. The liver was affected in 97.8% of these patients. Risk factors for metastasis were the anterior site of the tumor, its volume greater than 0.4 cc and the presence of retinal detachment at diagnosis. The secondary enucleation rate at 10 years was 13.23%, mainly attributable to secondary neovascular glaucoma. The local recurrence rate was 6%. The visual acuity rate in 42.1% of patients was better than 20/100 at 10 years. Visual loss was mainly due to postradiation maculopathy and neuropathy.

CONCLUSION

Our study confirms the long-term results found in the literature on proton beam radiation. This therapy allows good tumor control, an excellent eye retention rate, and good final visual acuity for approximately half of the patients.

Modern radiation treatment planning and delivery--from Röntgen to real time

The field of radiation oncology has advanced exponentially since the discovery of X-rays just over 100 years ago. With the advent of three-dimensional treatment planning, the therapeutic index was increased by dose escalation and more accurate shielding of normal tissues. Now, even greater advances are under way with IMRT, image-guided radiation therapy, delineation and control of organ motion, and real-time imaging. Similarly, the use of particle therapies such as protons has the potential to effect even more accurate dose distributions. Clinical studies investigating these modalities will likely further increase the efficacy of radiation in years to come.

Radiation Therapy With Charged Particles

Charged particle beams can offer an improved dose conformation to the target volume as compared with photon radiotherapy, with better sparing of normal tissue structures close to the target. In addition, beams of ions heavier than (4)He exhibit a strong increase of the linear energy transfer in the Bragg peak as compared with the entrance region. These physical and biological properties are much more favorable than in photon radiotherapy. As a consequence, particle therapy with protons and heavy ions has gained increasing interest worldwide, and many clinical centers are considering introducing radiation therapy with charged particles. This contribution summarizes the physical and technical principles of charged particle therapy with protons and heavy ions. It briefly reviews the clinical experience gathered so far with proton therapy and gives a more detailed summary of the recent results in carbon ion therapy of skull base tumors, head and neck tumors, non-small-cell lung cancer, hepatocellular carcinomas, bone and soft-tissue sarcomas, and prostate cancer.

Facteurs pronostiques du mélanome malin de l’uvée

INTRODUCTION

We conducted a retrospective study on the clinical factors influencing the local and general prognosis of patients treated for uveal melanoma with a preliminary analysis of the prognostic value of monosomy 3.

PATIENTS

and method: The patients sent to Curie Institute for uveal melanoma have a complete initial clinical evaluation, conservative management by radiotherapy or enucleation, and local and general long-term follow-up. Over the last 5 years, the status of chromosome 3 has been assessed by FISH in the tumors of enucleated patients. Findings concerning the initial workup, treatment, and follow-up are recorded prospectively. We conducted a retrospective study with multivariate analysis of the clinical factors influencing local recurrence, ocular conservation metastasis, and survival and studied the effect of monosomy 3.

RESULTS

A total of 2241 patients were registered with a median follow-up of 72 months. Of these patients, 92.8% had conservative management with iodine 125 brachytherapy or proton beam therapy and 7.2% of the patients had enucleation (n=160). Tumors from 120 patients were studied for the status of chromosome 3 by FISH. The overall survival rate was 76.3% and the metastatic rate was 19.5%. The clinical factors influencing survival were the size and location of the tumor, age of the patient, gender, and initial treatment. The factors influencing the metastatic risk were the same plus retinal detachment and local recurrence. Monosomy 3 was a significant risk factor for metastatic disease.

DISCUSSION

This study found the usual risk factors with the difference that location on the equator seems to be of worse prognosis than ciliary body involvement for survival and metastasis. In addition, the initial retinal detachment appears to be a risk factor for local recurrence and metastasis. At present, the evaluation of chromosome 3 is available for enucleated tumors but it could probably be done on needle biopsy performed during conservative management as well.

CONCLUSION

This study confirms previous results on the prognostic factors of uveal melanoma and on the value of monosomy 3. The increasingly precise identification of a group of high-risk patients should allow us to propose adjuvant therapy and to adapt follow-up.