Dose De-Escalation With Gamma Knife Radiosurgery in the Treatment of Choroidal Melanoma

Is It Possible to Preserve Vision without Compromising Metastases-Free Survival by Use of Fully Fractionated Stereotactic Radiotherapy for Posterior Choroidal Melanoma?

Introduction

Stereotactic radiotherapy (SRT) is used for choroidal melanoma (CM) abutting the optic nerve. Visual acuity (VA) deterioration to ≤6/60 is common. We report a pilot study of reduced-dose SRT using 2 Gy/day, aiming to preserve vision without compromising survival.

Method

60 Gy SRT was delivered in 30 fractions over 6 weeks. Liver metastasis surveillance was annual ultrasound. The primary endpoint was 5-year metastasis-free survival (5yMFS). Secondary endpoints were 2-year freedom from local progression (2yFFLP), VA, enucleation rate, and radiation toxicity.

Results

Twenty adults aged ≤70 years with T1-T2M0 CM without diabetes mellitus were enrolled. Median follow-up was 5.1 years. About 85% and 90% of tumours were ≤3 mm of the macula and optic disc, respectively. Median tumour height was 2.2 mm (range 1.0-4.4 mm), and median basal diameter was 8.2 mm (range: 4.3-15.0 mm). 5yMFS was 88% (95% CI: 61-97), and the 2yFFLP rate was 90% (95%: CI 66-97). There were three enucleations for disease progression. Final VA in retained eyes was ≥6/7.5 in 6 (30%), 6/9 to 6/12 in 5 (25%), 6/15 to 6/48 in 2 (10%), and ≤6/60 in 4 (20%) eyes. Retinopathy was the main cause of vision loss besides tumour progression.

Conclusion

Meaningful vision was preserved 5 years after SRT, despite high-risk tumour locations for vision loss. 2yFFLP and 5yMFS were acceptable. This dose fractionation warrants further investigation.

Current and Emerging Radiotherapy Options for Uveal Melanoma

What treatment options are there for patients having uveal melanoma? A randomized, prospective, multi-institutional clinical trial (COMS) showed no difference in survival between brachytherapy and enucleation for medium-sized lesions. With the obvious benefit of retaining the eye, brachytherapy has flourished and many different approaches have been developed such as low-dose-rate sources using alternate low-energy photon-emitting radionuclides, different plaque designs and seed-loading techniques, high-dose-rate brachytherapy sources and applicators, and low- and high-dose-rate beta-emitting sources and applicators. There also have been developments of other radiation modalities like external-beam radiotherapy using linear accelerators with high-energy photons, particle accelerators for protons, and gamma stereotactic radiosurgery. This article examines the dosimetric properties, targeting capabilities, and outcomes of these approaches. The several modalities examined herein have differing attributes and it may be that no single approach would be considered optimal for all patients and all lesion characteristics.

Magnetic Resonance Imaging in the Clinical Care for Uveal Melanoma Patients-A Systematic Review from an Ophthalmic Perspective

Conversely to most tumour types, magnetic resonance imaging (MRI) was rarely used for eye tumours. As recent technical advances have increased ocular MRI's diagnostic value, various clinical applications have been proposed. This systematic review provides an overview of the current status of MRI in the clinical care of uveal melanoma (UM) patients, the most common eye tumour in adults. In total, 158 articles were included. Two- and three-dimensional anatomical scans and functional scans, which assess the tumour micro-biology, can be obtained in routine clinical setting. The radiological characteristics of the most common intra-ocular masses have been described extensively, enabling MRI to contribute to diagnoses. Additionally, MRI's ability to non-invasively probe the tissue's biological properties enables early detection of therapy response and potentially differentiates between high- and low-risk UM. MRI-based tumour dimensions are generally in agreement with conventional ultrasound (median absolute difference 0.5 mm), but MRI is considered more accurate in a subgroup of anteriorly located tumours. Although multiple studies propose that MRI's 3D tumour visualisation can improve therapy planning, an evaluation of its clinical benefit is lacking. In conclusion, MRI is a complementary imaging modality for UM of which the clinical benefit has been shown by multiple studies.

Preliminary Results of Uveal Melanoma Treated With Iodine-125 Plaques: Analysis of Disease Control and Visual Outcomes With 63 Gy to the Target Volume

Purpose

Our purpose was to review the preliminary outcomes of patients with uveal melanoma treated with iodine-125 plaques using a novel treatment planning approach.

Methods and Materials

This was a single institution, retrospective review of patients treated with iodine-125 brachytherapy for uveal melanoma from November 2016 to February 2019. We used 3-dimensional treatment planning with the Eye Physics Plaque Simulator to ensure that a minimum of 63 Gy covered a 2-mm circumferential tumor margin and the apex height of the tumor over 94 hours. Primary endpoints were local failure, systemic metastasis, final visual acuity (VA), and radiation retinopathy. Associations between primary endpoints and tumor characteristics/radiation dose were performed using univariate analysis.

Results

Sixty-nine patients were included in the analysis. Mean largest basal diameter was 11.67 mm (range, 6-18; median, 12), and the average tumor thickness to the inner sclera was 3.18 mm (range, 0.5-9.3; median, 2.8). Molecular testing that was successfully performed in 59 patients revealed that 27% (16 of 59) had class 2 gene expression profile designation. Average follow-up posttreatment was 28.3 months (range, 4-46; median, 29), with 6% (4 of 69) developing local failure and 6% (4 of 69) developing metastasis over this duration. Average final VA (0.57 logMAR [Snellen 20/74]; range, 0-2.9; median, 0.3) was decreased from baseline (0.34 logMAR [Snellen 20/44]; range, 0-2.3; median, 0.1), and 48% (33 of 69) developed radiation retinopathy. Fifty percent of patients had a final VA 20/40 or better and 22% had a final VA 20/200 or worse.

Conclusions

In patients with uveal melanoma, preliminary results with brachytherapy using Eye Physics plaques with a treatment plan that delivers 63 Gy to a 2-mm circumferential tumor margin and the tumor apex suggest effective disease control and favorable VA outcomes.

Orbital indications

GKNS for uveal melanoma has become a recognized valued treatment which avoids enucleation of the eye. In the early days, the eccentric location of these tumors made treatment difficult, but Gamma Knife Perfexion has solved that problem. It is known that larger tumors and tumors with an anterior location have a worse prognosis. GKNS has also been of rather unexpected benefit in optic nerve gliomas that require treatment. Choroidal hemangiomas may benefit from treatment as can secondary glaucoma. It has also been found to be beneficial in the treatment of thyrotoxic ophthalmopathy.

Radiation therapy for uveal melanoma: a review of treatment methods available in 2021

PURPOSE OF REVIEW

Radiation therapy has become the standard of care for the treatment of uveal melanoma. We intend to outline the current radiation therapy methods that are employed to treat uveal melanoma. We will outline their relative benefits over one another. We will also provide some background about radiation therapy in general to accustom the ophthalmologists likely reading this review.

RECENT FINDINGS

Four main options exist for radiation therapy of uveal melanoma. Because the eye is a small space, and because melanomas are relatively radioresistant, oncologists treating uveal melanoma must deliver highly focused doses in high amounts to a small space. Therapies incorporating external beams include proton beam therapy and stereotactic radiosurgery. Stereotactic radiosurgery comes in two forms, gamma knife therapy and cyberknife therapy. Radiation may also be placed directly on the eye surgically via plaque brachytherapy. All methods have been used effectively to treat uveal melanoma.

SUMMARY

Each particular radiotherapy technique employed to treat uveal melanoma has its own set of benefits and drawbacks. The ocular oncologist can choose amongst these therapies based upon his or her clinical judgment of the relative risks and benefits. Availability of the therapy and cost to the patient remain significant factors in the ocular oncologist's choice.

Gamma knife radiosurgery for uveal melanomas and metastases: a systematic review and meta-analysis

BACKGROUND

Gamma knife radiosurgery is regarded as the gold-standard stereotactic radiosurgery modality for the treatment of intracranial tumours, and its use has been expanded for the treatment of intraocular malignancies. The aim of this study was to systematically evaluate the efficacy, outcomes, and complications of gamma knife radiosurgery for uveal melanomas and metastases.

METHODS

We did a systematic review and meta-analysis to aggregate the clinical outcomes of patients with uveal melanomas or intraocular metastases treated primarily with gamma knife radiosurgery. We searched MEDLINE and Embase for studies published between Sept 1, 1960, and Feb 1, 2020, reporting the use of gamma knife radiosurgery as primary treatment for uveal melanoma or uveal metastases. The search was restricted to clinical studies and relevant grey literature published in English. Studies reporting treatment of benign tumours, extraocular tumours, or other forms of stereotactic radiosurgery were excluded to reduce heterogeneity. No restrictions were placed on participant criteria. Local tumour control and tumour regression were extracted as the primary outcomes and analysed via a random-effects meta-analysis of proportions using the DerSimonian and Laird method with a Freeman-Tukey double arcsine transformation. This study is registered with PROSPERO, CRD42019148165.

FINDINGS

Our search returned 454 studies, of which 109 were assessed for full-text eligibility. 52 studies, reporting on 1010 patients with uveal melanoma and 34 intraocular metastases, were eligible for systematic review. 28 studies were included in the meta-analysis. 840 of 898 patients (0·96, 95% CI 0·94-0·97; I²=16%) from 19 studies had local control, and 378 of 478 patients (0·81, 0·70-0·90; I²=83%) from 16 studies experienced tumour regression.

INTERPRETATION

Gamma knife radiosurgery is an efficacious primary method of treating uveal melanomas and intraocular metastases, with reliable tumour control rates. Randomised controlled trials should further evaluate the safety and efficacy of gamma knife radiosurgery in this setting.

FUNDING

The Rhodes Trust and the Howard Brain Sciences Foundation.

Primary Episcleral Melanoma Consistent with Uveal Melanoma Mutations Treated by Excision and Gamma Knife Stereotactic Radiosurgery

Ocular melanocytosis has traditionally been associated with increased risk of developing uveal melanoma; however, rarely primary episcleral melanoma has been reported in the literature. Herein, we present the third case of primary episcleral melanoma treated by complete excision and cryotherapy. In contrast to previous cases, we obtained molecular genetic testing which revealed a GNA-11 mutation, and gene expression profiling resulted in a Class 2 PRAME positive tumor diagnosis. These two tests which have never been performed on previous cases, support lineage similar to uveal melanoma. In addition, we are the first case to report treatment of the surgical bed and surrounding orbital tissue with Gamma Knife stereotactic radiotherapy to both treat residual tissue and decrease risk of recurrence.

Gamma Knife Radiosurgery for Uveal Melanoma: A Retrospective Review of Clinical Complications in a Tertiary Referral Center

Introduction

Gamma knife radiosurgery (GKR) has shown promising results in the treatment of intraocular uveal melanoma (UM) in terms of local tumor control. However, GKR is not free from potentially sight-threatening side effects, including cataract, dry eye disease, vitreous hemorrhage, radiation retinopathy (RR), radiation maculopathy (RM), optic neuropathy, and neovascular glaucoma. The aim of this paper is to report our 20-year experience in UM management with GKR focusing on the rate of clinical treatment-induced complications.

Methods

Single-center, retrospective, observational study, including all patients with UM treated at the Ocular Oncology and Uveitis Service, in the Department of Ophthalmology of the San Raffaele Scientific Institute, Milan from September 1993 to September 2018. Clinical charts comprised complete ophthalmological examination with measurement of best-corrected visual acuity, slit-lamp biomicroscopy, intraocular pressure measurement, gonioscopy, and indirect ophthalmoscopy at each visit. B-scan ultrasound (Aviso S, 10 MHz probe; Paris, France), optical coherence tomography (Heidelberg Spectralis; Heidelberg Engineering, Heidelberg, Germany), retinography, and fundus fluorescein angiography (standard or ultra-widefield [UWF; California, Optos, Dunfermline, Scotland, UK]) were performed aiding in the diagnosis of complications.

Results

Overall, 194 patients (100 males, 51.6%) were reviewed. The median age at the time of the treatment was 65 years (range 27-89) and all participants were Caucasian. In 185 eyes (95.4%), the tumor was primarily located at the choroid. The median follow-up was 57.6 months; radiation-induced complications were found in 145 eyes (74.7%). Radiation-induced cataract and RR were the most frequent events, with a relative incidence of 41.2 and 34.5%, respectively, followed by neovascular glaucoma (27.3%), optic neuropathy (18.6%), RM (11.4%), vitreous hemorrhage (14.4%), phthisis bulbi (7.7%), hyphema (0.5%), and corneal melting (0.5%). The shorter onset of side effects involved the optic nerve (median 14.9 months) and the macula (median 13.7 months).

Conclusion

Despite modern and advanced strategies introduced to limit GKR side effects, cataract and RR still represent a serious limitation of this treatment. Incidence of RR was higher in our cohort compared to other reports, probably due to increased diagnosis rate permitted by UWF retinal imaging.

3D WrapTM Ultra-Widefield Reconstruction in Stereotactic Radiosurgery for Choroidal Melanoma

Choroidal melanoma (CM) is the most commonly diagnosed primary intraocular malignancy in adults. Gamma knife radiosurgery (GKR) has demonstrated reliable results in the treatment of CM, but it is limited by the risk of radiation-induced ocular complications. To optimize the dose of radiation focused on the tumor, and limit side effects, the eye should be properly immobilized before treatment. A recently released ultra-widefield imaging instrument (Optomap California; Optos, Dunfermline, Scotland, UK) allows for an interactive three-dimensional (3D) virtual reconstruction of the globe, called 3D Wrap^TM. The authors share their experience with this rapid, reliable, and relatively easy support in planning globe positioning before GKR treatment.

Gamma Knife Stereotactic Radiosurgery for the Treatment of Primary and Metastatic Ocular Malignancies

BACKGROUND

Gamma knife radiosurgery (GKR) can be used for precise targeting of malignant lesions of the CNS when brachytherapy is not an appropriate option.

OBJECTIVES

This study reports treatment technique, efficacy, and radiation-induced adverse effects in patients with primary and metastatic ocular lesions treated with Leksell GKR.

METHODS

A retrospective, single-institution review was conducted of 28 patients with primary or metastatic ocular disease, treated from 2000 to 2014. The dose to margin was 17-27 Gy (maximum dose 28-54 Gy). Primary outcomes included overall survival (OS), local control, progression-free survival (PFS), and enucleation.

RESULTS

The median age at diagnosis was 70 years, and the median follow-up was 26.4 months. Of the 28 patients, 11 (39%) had metastatic ocular disease, and 17 (61%) were diagnosed with primary ocular melanoma (stage T2a-T4e). The average maximum dose and dose to margin were 41 and 21 Gy, respectively. The mean dose to the optic nerve was 12.6 Gy. The 5-year OS was 46% (95% CI: 23.6-68.4%) for the entire cohort; the 5-year PFS for M0 patients who presented with primary ocular melanoma lesions was 90% (95% CI: 71-100%). Only 1 patient required enucleation after radiation treatment.

CONCLUSION

GKR is an effective option, with acceptable levels of toxicity, in the treatment of primary and metastatic ocular lesions.

Predictors of radio-induced visual impairment after radiosurgery for uveal melanoma

Aims

The aim of the present work is to assess the main predictors of the most clinically relevant radio-induced effects after Gamma Knife stereotactic radiosurgery (GKRS) for uveal melanoma (UM).

Materials and methods

Medical records and three-dimensional dosimetry data of critical structures of 66 patients were retrospectively reviewed. Cox’s proportional hazard model was used to identify clinical and dosimetric variables as independent risk factor for GKRS-related complications.

Results

The fraction of the posterior segment receiving more than 20Gy (V20), Bruch’s membrane rupture and tumour thickness were significant prognostic factors for neovascular glaucoma. A clear relationship with the dose received by 1% of the optic nerve (D1%) was found for radiation retinopathy and papillopathy. Multivariables models resulted for visual acuity (VA) reduction >20% of the basal value and for complete VA loss, both including largest tumour diameter and D1% to the optic nerve. The predictive model for complete VA loss includes also Bruch’s membrane rupture. An alternative model for complete visual acuity loss, including the optic nerve-prescription isodose minimum distance, was also suggested.

Conclusions

We found clinical and dosimetric variables to clearly predict the risk of the main side effects after GKRS for UM. These results may provide dose constraints to critical structures, potentially able to reduce side effects. Constraining D1% to the optic nerve below 12-13Gy may result in a dramatic reduction of blindness risk, while reducing V20 of the posterior segment of the bulb could limit the neovascular glaucoma onset.

Die Geschichte der Ophthalmoonkologie an der Univ.-Augenklinik Graz

Einleitung

Der Beginn der organerhaltenden Therapie an der Univ.-Augenklinik datiert auf das Jahr 1985 mit der Einführung der Ruthenium 106 Applikatoren (Lommatzsch, Vormun) zurück.

Der Autor skizziert in zeitlicher Abfolge die Einführung und gemeinsame Entwicklung verschiedener Arten von organerhaltender Therapien und endet mit neuen Therapieansätzen des Retinoblastoms und des metastasierenden Aderhautmelanoms.

Methodik

Die Vorstände der Univ.-Augenklinik beginnend mit Hofmann (1964–1987) unterstützten den Paradigmenwechsel von einem radikalchirurgischen Konzept (Enukleation) bei intraokularen Tumoren zu einem organerhaltenden Konzept trotz Fehlens von großen Studien mit hoher Evidenz. Zuweisende FachärztInnen waren zu Recht im Zweifel über die Sinnhaftigkeit dieser neuen Therapiekonzepte, unterstützen jedoch mit ihren PatientInnen Zuweisungen den neuen Arbeitsschwerpunkt bzw. den organerhaltenden Therapieansatz bis zum heutigen Tag.

Ergebnisse

Aderhautmelanom: 1985 wurde die organerhaltende Therapie mittels Ruthenium 106 Applikatoren in Graz für kleine und mittelgroße Aderhautmelanome mit aequatorialler und anteriorer Lokalisation eingeführt, ab 1992 war die Gamma Knife Radiochirurgie alternativ zur Protonen- und Photonentherapie an der Univ. Klinik für Neurochirurgie in Graz verfügbar und wurde mit Beiträgen anderer Tumorzentren für die Behandlung von großen Aderhautmelanomen oder solchen mit posteriorer Lokalisation entwickelt.

Die transpupillare Thermotherapie (TTT) wurde 1995 in Leiden von Osterhuis und Journée-de Korver für die Behandlung von flachen posterior lokalisierten Melanomen im Tiermodell entwickelt. Die Therapie geriet auf Grund einer erhöhten Rate von Rezidiven in einzelnen Tumorzentren in Mißkredit und Vergessenheit, sollte jedoch auf Grund guter eigener Erfahrungen und der Einführung der TTT bei der Behandlung von Retinoblastomen in Hinblick auf Technik und Indikationen neuerlich evaluiert werden.

Endoresektion: Aderhautmelanome werden nach Vorbestrahlung wegen des großen Tumorvolumens bzw. einer persistierenden Amotio mittels Vitrektomie Techniken reserziert, als Bestrahlungstechnik wurde in Graz und in Essen das Gamma Knife verwendet.

Biopsien werden seit einigen Jahren für genetische und mikrobiologische Untersuchungen durchgeführt, neue mikrobiologische Erkenntnisse werden zur Entwicklung neuer systemischer Therapiekonzepte führen.

Retinoblastom: Im Gegensatz zum Aderhautmelanom erwies sich die adjuvante Chemotherapie beim Retinoblastom als hoch wirksam v. a. in der Volumsreduktion der Tumoren.

Die Brachytherapie mit Ruthenium 106 Schalen, die 3‑fach Kryotherapie bzw. die Lasertherapie werden bereits seit Jahrzehnten an der Univ.-Augenklinik als organerhaltende Lokaltherapien durchgeführt, seit kurzem komplettiert die TTT (mit oder ohne simultane Chemotherapie) das Spektrum der fokalen Therapien. Neue Therapiekonzepte wie die intrabulbäre Chemotherapie (bereits in Anwendung) sowie die intraarterielle Chemotherapie (steht kurz vor der Implementierung) sind bereits in Routine.

Seit 2003 werden erstmals Retinoblastome in einer Therapie Optimierungsstudie RBA2003 (die das Department für Hämato‑/Onkologie der Univ. Kinderklinik Graz zusammen mit der Univ.-Augenklinik entwickelt hat) in Graz behandelt. Das Univ. Klinikum Graz etabliert sich als Referenzzentrum für Retinoblastome und Pseudoretinoblastome in Österreich und dem umgebenden Ausland und erhielt Anfragen und PatientInnen Zuweisungen aus den Alpe Adria Ländern sowie Schweiz, Bulgarien, Tschechien, Rumänien, Ukraine und Rußland. Wedrich, derzeitiger Vorstand der Univ.-Augenklinik Graz, förderte die Entwicklung des Retinoblastom Kompetenz Zentrums in personeller, instrumenteller und logistischer Hinsicht.

2015 entwickelte das Klinikum Essen ein auf das Protokoll RBA2003 aufbauendes, erweitertes internationales Protokoll, nach dem nun PatientInnen aus Essen und Graz gemeinsam behandelt, evaluiert und nachkontrolliert werden. Dieses wiederum wird in einem EU-Antrag, initiert von Chandada (Buenos Aires, Barcelona) für eine einheitliche Behandlung des Retinoblastoms in Europa berücksichtigt.

2005 engagierte sich die Arbeitsgruppe erstmals in Mosambique, Afrika folgend einer Bitte der NGO, Licht für die Welt, die Rahmenbedingungen für die Etablierung eines Retinoblastomzentrums zu prüfen.

2008 wurde am LKH Univ. Klinikum Graz ein Forschungsfeld Onkologie etabliert, in weiterer Folge das Comprehensive Cancer Center (CCC) der MUG gegründet, in das die Ophthalmoonkologie thematisch eingegliedert ist.

Schlussfolgerung

Das vor 32 Jahren am LKH Univ.-Klinikum Graz etablierte Konzept der organerhaltenden Therapie erfuhr 13 Jahre später die Bestätigung durch die bislang größte multizentrische Studie (COMS Studie) in den USA, wonach kein Unterschied in Hinblick auf Überleben zwischen Enukleation und bulbuserhaltender Therapie mit Jod 125 Schalen bei kleinen und mittelgroßen Aderhautmelanomen gefunden wurde. Die seit über 30 Jahren unveränderte (z. T. sehr schlechte) Prognose kann möglicherweise in absehbarer Zeit durch neue Medika verbessert werden. Basis für diese erfreulichen Entwicklungen sind neue bahnbrechende Erkenntnisse aus der zytogenetischen und molekularbiologischen Forschung.

Dosimetric and radiobiologic comparison of 103Pd COMS plaque brachytherapy and Gamma Knife radiosurgery for choroidal melanoma

PURPOSE

Plaque brachytherapy (BT) and Gamma Knife radiosurgery (GKRS) are highly conformal treatment options for choroidal melanoma. This study objectively compares physical dose and biologically effective dose (BED) distributions for these two modalities.

METHODS AND MATERIALS

Tumor and organ-at-risk (OAR) dose distributions from a CT-defined reference right eye were compared between ¹⁰³Pd COMS (Collaborative Ocular Melanoma Study Group) plaques delivering 70 Gy (plaque heterogeneity corrected) over 120 h to the tumor apex and GKRS plans delivering 22 Gy to the 40% isodose line for a representative sample of clinically relevant choroidal melanoma locations and sizes. Tumor and OAR biologically effective dose-volume histograms were generated using consensus radiobiologic parameters and modality-specific BED equations.

RESULTS

Published institutional prescriptive practices generally lead to larger tumor and OAR physical doses from COMS BT vs. GKRS. Radiobiologic dose conversions, however, revealed variable BEDs. Medium and large tumors receive >1.3 times higher BEDs with COMS BT vs. GKRS. OAR BEDs have even greater dependence on tumor size, location, and treatment modality. For example, COMS BT maximum BEDs to the optic nerve are lower than from GKRS for large anterior and all posterior tumors but are higher for anterior small and medium tumors.

CONCLUSIONS

BT and GKRS for choroidal melanoma have different physical dose and BED distributions with potentially unique clinical consequences. Using published institutional prescriptive practices, neither modality is uniformly favored, although COMS BT delivers higher physical doses and BEDs to tumors. These results suggest that lowering the physical prescription dose for COMS BT to more closely match the BED of GKRS might maintain equivalent tumor control with less potential morbidity.

Disease control and toxicity outcomes using ruthenium eye plaque brachytherapy in the treatment of uveal melanoma

PURPOSE

Ruthenium-106 ((106)Ru) eye plaques have the potential to achieve excellent tumor control with acceptable radiation toxicity. We evaluated our experience in the management of uveal melanoma treated with (106)Ru brachytherapy.

METHODS AND MATERIALS

The records of 40 patients with uveal melanoma treated with brachytherapy using (106)Ru plaques from 2003 to 2007 at University of Texas MD Anderson Cancer Center were reviewed. Endpoints assessed included tumor control and toxicity.

RESULTS

Median ophthalmologic follow-up was 67 months. Actuarial 5-year rates of local control (LC), progression-free survival (PFS), and overall survival (OS) were 97%, 94%, and 92%. There were 3 deaths, 2 related to melanoma. Fifteen patients experienced clinically significant visual loss; no patients were diagnosed with neovascular glaucoma, and 1 patient developed a clinically significant radiation-associated cataract. No patient required enucleation.

CONCLUSIONS

We report the largest published US cohort of patients treated with (106)Ru plaque brachytherapy for uveal melanoma. Tumor control was excellent, and toxicity was acceptably low. These data support the reintroduction of (106)Ru into clinical practice for ocular melanoma.

Keeping an eye on the ring: COMS plaque loading optimization for improved dose conformity and homogeneity

PURPOSE

To improve tumor dose conformity and homogeneity for COMS plaque brachytherapy by investigating the dosimetric effects of varying component source ring radionuclides and source strengths.

MATERIAL AND METHODS

The MCNP5 Monte Carlo (MC) radiation transport code was used to simulate plaque heterogeneity-corrected dose distributions for individually-activated source rings of 14, 16 and 18 mm diameter COMS plaques, populated with (103)Pd, (125)I and (131)Cs sources. Ellipsoidal tumors were contoured for each plaque size and MATLAB programming was developed to generate tumor dose distributions for all possible ring weighting and radionuclide permutations for a given plaque size and source strength resolution, assuming a 75 Gy apical prescription dose. These dose distributions were analyzed for conformity and homogeneity and compared to reference dose distributions from uniformly-loaded (125)I plaques. The most conformal and homogeneous dose distributions were reproduced within a reference eye environment to assess organ-at-risk (OAR) doses in the Pinnacle(3) treatment planning system (TPS). The gamma-index analysis method was used to quantitatively compare MC and TPS-generated dose distributions.

RESULTS

Concentrating > 97% of the total source strength in a single or pair of central (103)Pd seeds produced the most conformal dose distributions, with tumor basal doses a factor of 2-3 higher and OAR doses a factor of 2-3 lower than those of corresponding uniformly-loaded (125)I plaques. Concentrating 82-86% of the total source strength in peripherally-loaded (131)Cs seeds produced the most homogeneous dose distributions, with tumor basal doses 17-25% lower and OAR doses typically 20% higher than those of corresponding uniformly-loaded (125)I plaques. Gamma-index analysis found > 99% agreement between MC and TPS dose distributions.

CONCLUSIONS

A method was developed to select intra-plaque ring radionuclide compositions and source strengths to deliver more conformal and homogeneous tumor dose distributions than uniformly-loaded (125)I plaques. This method may support coordinated investigations of an appropriate clinical target for eye plaque brachytherapy.

Dosimetry of (125)I and (103)Pd COMS eye plaques for intraocular tumors: report of Task Group 129 by the AAPM and ABS

Dosimetry of eye plaques for ocular tumors presents unique challenges in brachytherapy. The challenges in accurate dosimetry are in part related to the steep dose gradient in the tumor and critical structures that are within millimeters of radioactive sources. In most clinical applications, calculations of dose distributions around eye plaques assume a homogenous water medium and full scatter conditions. Recent Monte Carlo (MC)-based eye-plaque dosimetry simulations have demonstrated that the perturbation effects of heterogeneous materials in eye plaques, including the gold-alloy backing and Silastic insert, can be calculated with reasonable accuracy. Even additional levels of complexity introduced through the use of gold foil "seed-guides" and custom-designed plaques can be calculated accurately using modern MC techniques. Simulations accounting for the aforementioned complexities indicate dose discrepancies exceeding a factor of ten to selected critical structures compared to conventional dose calculations. Task Group 129 was formed to review the literature; re-examine the current dosimetry calculation formalism; and make recommendations for eye-plaque dosimetry, including evaluation of brachytherapy source dosimetry parameters and heterogeneity correction factors. A literature review identified modern assessments of dose calculations for Collaborative Ocular Melanoma Study (COMS) design plaques, including MC analyses and an intercomparison of treatment planning systems (TPS) detailing differences between homogeneous and heterogeneous plaque calculations using the American Association of Physicists in Medicine (AAPM) TG-43U1 brachytherapy dosimetry formalism and MC techniques. This review identified that a commonly used prescription dose of 85 Gy at 5 mm depth in homogeneous medium delivers about 75 Gy and 69 Gy at the same 5 mm depth for specific (125)I and (103)Pd sources, respectively, when accounting for COMS plaque heterogeneities. Thus, the adoption of heterogeneous dose calculation methods in clinical practice would result in dose differences >10% and warrant a careful evaluation of the corresponding changes in prescription doses. Doses to normal ocular structures vary with choice of radionuclide, plaque location, and prescription depth, such that further dosimetric evaluations of the adoption of MC-based dosimetry methods are needed. The AAPM and American Brachytherapy Society (ABS) recommend that clinical medical physicists should make concurrent estimates of heterogeneity-corrected delivered dose using the information in this report's tables to prepare for brachytherapy TPS that can account for material heterogeneities and for a transition to heterogeneity-corrected prescriptive goals. It is recommended that brachytherapy TPS vendors include material heterogeneity corrections in their systems and take steps to integrate planned plaque localization and image guidance. In the interim, before the availability of commercial MC-based brachytherapy TPS, it is recommended that clinical medical physicists use the line-source approximation in homogeneous water medium and the 2D AAPM TG-43U1 dosimetry formalism and brachytherapy source dosimetry parameter datasets for treatment planning calculations. Furthermore, this report includes quality management program recommendations for eye-plaque brachytherapy.