Irradiation of choroidal melanoma with iodine 125 ophthalmic plaque

Comparative Study of Ultrasonography and Ultra-Widefield Fundus Photographs for Measurements of the Diameter of Choroidal and Retinal Tumors

INTRODUCTION

Measurement of the largest basal dimension (LBD) of intraocular tumors is important as a prognostic parameter. To evaluate the potential value of true color ultra-widefield fundus photography for measuring tumors, we compared LBD measurements of choroidal and retinal tumors using a color ultra-widefield fundus camera with clinical estimation based on indirect ophthalmoscopy and standardized ophthalmic ultrasound.

METHODS

The LBD of 148 choroidal and retinal tumors in 148 patients seen at Tongren Hospital were measured using ultra-widefield fundus photography and compared with measurements obtained using B-scan ultrasonography and clinical estimates based on indirect ophthalmoscopy.

RESULTS

Paired t-tests and Bland-Altman plots reveal that measurements from ultra-widefield fundus photographic images are not statistically different from clinical estimates and ultrasound measurements. The results also showed that, although not statistically significant, when the tumor boundary was clear, the height was < 3 mm, or the tumor was pigmented, measurement from ultra-widefield fundus photography tended to be greater than those obtained by ultrasound.

CONCLUSIONS

The LBD measurement using ultra-widefield fundus photography correlated well with ultrasonography and clinical estimation and could be used as a reliable tool for measuring the LBD of choroidal and retinal tumors.

Therapy of uveal melanoma A Review

The aim of intraocular melanoma therapy is to achieve local tumor control, reduce the risk of metastasis development, preserve the eyeball and possibly the visual function of the eye. The choice of therapeutic approach requires a comprehensive view and individual approach to each patient with uveal melanoma. Factors considered include local finding (location, tumor size and shape, tumor activity, central visual acuity, intraocular complications), age and the patients overall physical and psychological condition, as well as the patients wishes. The most widely used method of uveal melanoma treatment is radiotherapy. The effect of radiation is caused by the absorption of ionizing radiation energy, the effect of radiation on the cell is manifested by cell death (depletion), or by a cytogenetic information change (mutation). Brachytherapy uses scleral applicators with radionuclide - ruthenium (Ru-106) applicators dominate in Europe and iodine (I-125) applicators in the USA. In external radiotherapy, the source of ionizing radiation is outside the patients body. Both stereotactic radiosurgery and fractionated stereotactic radiotherapy are used. In the Czech Republic, treatment is carried out using Leksell gamma knife or CyberKnife, while proton therapy dominates in the world. The development of serious radiation complications (radiation retinopathy, neuropathy, neovascular glaucoma, toxic tumor syndrome, etc.) should be considered. Surgical therapy involves a variety of invasive procedures. Iridectomy is performed for iris melanoma. Anteriorly located choroidal melanomas and / or ciliary body melanomas can be resolved by transscleral resection (exoresection). For posterior choroidal melanomas, a combination of external tumor irradiation with pars plana vitrectomy is used. Enucleation is a method of choice in advanced tumors that cannot be effectively irradiated. Orbital exenteration is indicated in advanced tumors with extrabulbar spread or in relapsed tumor after previous enucleation.

New concepts in the diagnosis and management of choroidal metastases

The most frequent site of ocular metastasis is the choroid. The occurrence of choroidal metastases has increased steadily due to the longer survival of metastatic patients and the improvement of diagnostic tools. Fundoscopy, ultrasonography, and fluorescein angiography are now complemented by indocyanine green angiography and optical coherence tomography. Choroidal tumor biopsy may also confirm the metastatic nature of the tumor and help to determine the site of the primary malignancy. There is currently no consensus on the treatment strategy. Most patients have a limited life expectancy and for these complex treatments are generally not recommended. However, recent advances in systemic therapy have significantly improved survival of certain patients who may benefit from an aggressive ocular approach that could preserve vision. Although external beam radiation therapy is the most widely used treatment, more advanced forms of radiotherapy that are associated with fewer side effects can be proposed in select cases. In patients with a shorter life expectancy, systemic therapies such as those targeting oncogenic drivers, or immunotherapy can induce a regression of the choroidal metastases, and may be sufficient to temporarily decrease visual symptoms. However, they often acquire resistance to systemic treatment and ocular relapse usually requires radiotherapy for durable control. Less invasive office-based treatments, such as photodynamic therapy and intravitreal injection of anti-VEGF, may also help to preserve vision while reducing time spent in medical settings for patients in palliative care. The aim of this review is to summarize the current knowledge on choroidal metastases, with emphasis on the most recent findings in epidemiology, pathogenesis, diagnosis and treatment.

Feasibility study of a non-invasive eye fixation and monitoring device using a right-angle prism mirror for intensity-modulated radiotherapy for choroidal melanoma

We aimed to describe the feasibility and efficacy of a novel non-invasive fixation and monitoring (F-M) device for the eyeballs (which uses a right-angle prism mirror as the optic axis guide) in three consecutive patients with choroidal melanoma who were treated with intensity-modulated radiotherapy (IMRT). The device consists of an immobilization shell, a right-angle prism mirror, a high magnification optical zoom video camera, a guide lamp, a digital voice recorder, a personal computer, and a National Television System Committee standard analog video cable. Using the right-angle prism mirror, the antero-posterior axis was determined coincident with the optic axis connecting the centers of the cornea and pupil. The axis was then connected to the guide light and video camera installed on the couch top on the distal side. Repositioning accuracy improved using this method. Furthermore, the positional error of the lens was markedly reduced from ±1.16, ±1.68 and ±1.11 mm to ±0.23, ±0.58 and ±0.26 mm in the horizontal direction, and from ±1.50, ±1.03 and ±0.48 mm to ±0.29, ±0.30 and ±0.24 mm in the vertical direction (Patient #1, #2 and #3, respectively). Accordingly, the F-M device method decreased the planning target volume size and improved the dose-volume histogram parameters of the organ-at-risk via IMRT inverse planning. Importantly, the treatment method was well tolerated.

Iodine-125 Brachytherapy for Uveal Melanoma: A Systematic Review of Radiation Dose

AIM

To investigate whether lower radiation doses may yield similar outcome measures to those from the COMS trial.

METHODS

A literature review of English language articles was performed using the PubMed database of the U.S. National Library of Medicine and the Cochrane Central Register of Controlled Trials using the following keywords: uveal melanoma, choroidal melanoma, primary uveal malignant melanoma, iodine-125 brachytherapy, local recurrence, local treatment failure, and local tumor control. The relationships between study local recurrence rate and median dosage were tested by linear regression, with each study weighted by the number of patients included.

RESULTS

Fifteen retrospective and prospective studies were selected for systematic review (2,662 patients). Ranges of reported mean or median radiation dose to tumor apex were 62.5-104.0 Gy. Local recurrence rates ranged from 0 to 24%. A 1.0-Gy increase in the average study dose was associated with a 0.14% decrease in local recurrence rate, which was not statistically significant (p value 0.336).

CONCLUSION

The gold standard empirically derived 85.0-Gy radiation dose for the treatment of uveal melanoma could be tested in a randomized study.

Adaptive replanning intensity-modulated radiotherapy for choroidal metastasis of breast cancer using optical coherence tomography

Swept source optical coherence tomography (SS-OCT) is a convenient method for precise, early-stage detection of choroidal metastatic lesions, involving assessment of tumor response, and for regular follow-up studies. Using information obtained with SS-OCT, we performed intensity-modulated radiotherapy (IMRT) for a patient with choroidal metastasis from breast cancer with more accuracy than had been previously possible. We made replanning adaptive radiotherapy (ART) three times based on the rapid tumor shrinkage detected by weekly assessments with SS-OCT. Accordingly, the planning target volume (PTV) decreased from 1.6 cm(3) to 0.61 cm(3) (38%), with 0.95 cm(3) (59%) and 0.75 cm(3) (46%) as intermediate values during the treatment course. The D0.1 cm3 of the right optic nerve was also reduced from 1.70 Gy/fraction to 0.69 Gy/faction, with 1.41 Gy/fraction and 1.29 Gy/fraction as intermediate values. Adaptive replanning IMRT made it possible to perform locally curative treatment of the metastatic choroidal lesion with a higher dose for the PTV, and a lower dose for organs at risk (OARs).

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.

Measurement of choroidal melanoma basal diameter by wide-angle digital fundus camera: a comparison with ultrasound measurement

PURPOSE

To compare the measurement of the basal diameter of choroidal melanoma, an important parameter for planning treatment and as a prognostic factor, by standardized ophthalmic ultrasound versus that obtained using a wide-angle fundus camera.

METHODS

The longest and shortest basal diameters of 104 consecutive choroidal melanomas of patients seen at the ocular oncology service of the Hadassah University Hospital were measured by B-scan ultrasound and compared with those measured by a wide-angle fundus camera (Panoret-1000). Each diameter was measured thrice by two ophthalmic photographers, and intra-observer and interobserver reproducibility were calculated as well.

RESULTS

The measurements of both the long and short diameters of the choroidal melanomas were significantly larger when measured by Panoret-1000 as compared with the B-scan ultrasound. There was no significant difference among the three measurements of each of the photographers. The interobserver reproducibility between the two photographers was high.

CONCLUSIONS

Our findings can be attributed to the larger extent of the pigmentation of the melanoma compared to its recognized elevation. Since pigmentation of choroidal melanoma is easier to recognize than its elevation, we assume that measurement by a wide-angle fundus camera is more accurate in pigmented tumors, and should be adopted for measuring the basal diameter of choroidal melanomas in planning treatment and follow-up.

Palladium-103 plaque radiotherapy for choroidal melanoma: an 11-year study

PURPOSE

To describe 11 years of experience with 103Pd ophthalmic plaque brachytherapy for intraocular melanoma.

METHODS AND MATERIALS

Since 1990, 152 patients have been diagnosed with uveal melanoma, found to be negative for metastatic disease, and treated with 103Pd radioactive plaque radiotherapy. This study presents the first 100 patients treated with 103Pd and followed for > or = 2 years. Plaques were sewn to the episclera to cover the base of the intraocular tumor. Treatment involved delivery of a mean apical radiation dose of 80.5 Gy during 5-7 days' continuous treatment. Patients were evaluated for local tumor control, visual acuity, radiation damage (retinopathy, optic neuropathy, cataract), and metastatic disease.

RESULTS

Patients in this series were followed for a mean of 4.6 years (55.4 months). 103Pd seeds were found to be equivalent to 125I with respect to plaque manufacture and ease of dosimetric calculations. We noted a local control rate of 96% and six secondary enucleations. Including the enucleated patients, the visual acuity evaluations revealed that 35% lost six or more lines of vision and 73% had vision of 20/200 or better.

CONCLUSION

Long-term results now exist describing the use of 103Pd plaque radiotherapy for uveal (iris, ciliary body, and choroidal) melanoma. Compared with the results from centers using 125I, patients in this series experienced equivalent local control rates and better visual function.

Intraoperative echographic localization of iodine-125 episcleral plaque for brachytherapy of choroidal melanoma

PURPOSE

To report intraoperative echographic localization of iodine-125 episcleral plaque for brachytherapy of choroidal melanoma.

METHODS

In a retrospective study, 117 eyes with medium-sized choroidal melanoma in 117 patients not participating in the Collaborative Ocular Melanoma Study underwent iodine-125 episcleral plaque radiotherapy with intraoperative echographic verification of plaque placement between January 1992 and December 1998 at the Bascom Palmer Eye Institute.

RESULTS

After initial plaque placement using standard localization techniques, intraoperative echography demonstrated satisfactory tumor-plaque apposition in 76% of eyes (89 of 117). In the 28 eyes (28 of 117, 24%) that required repositioning of the plaque, the extent of misplacement was less than 1 mm in 10 eyes, 1.1 to 3.0 mm in six eyes, and greater than 3 mm in eight eyes. Two eyes had tilting of the plaque, and in two additional eyes, although the plaque covered all tumor margins, the centration was considered suboptimal. Repositioning was necessary in 1 eye with an anteriorly located tumor (1 of 13, 7.7%) and in 20 eyes with peripapillary or posterior pole tumors (20 of 67, 26.3%). Anteriorly located tumors required plaque repositioning significantly less frequently than did posteriorly located tumors (P = .041). Misalignment involved one tumor margin in 23 eyes and two margins in five eyes. The most commonly misaligned margins were the lateral (35%) and posterior margins (26%). In no case was an anterior marginal misalignment documented. At a mean follow-up of 37 months, no tumor-related death or metastatic disease was noted. Two of the 117 patients (1.7%) had local tumor recurrence and underwent enucleation.

CONCLUSIONS

Intraoperative echography is an effective adjunct for localization and confirmation of tumor-plaque relationship. This technique facilitates the identification and correction of suboptimal plaque placement at the time of surgery, potentially minimizing treatment failures.

Autoradiography for iodine-125 seeds

To study the interior design of model 6702 and 6711 iodine-125 seeds contact autoradiographs were performed using mammography film. Improved resolution was obtained using a pin-hole camera with a hole of 0.1 mm x 0.1 mm. With these techniques, qualitative determination of the relative activity distribution within each seed was possible. The number of the activated resin spheres and the positions of the centers of these spheres can be exactly determined. A model calculation shows, that variations in the arrangement of the activated spheres within a seed have a moderate influence on the dose distribution at source distances below 10 mm. Knowing the exact source configuration may be useful when comparing dose calculations with measured data for model 6702 125I seeds which are currently employed in ophthalmic plaque and implant therapy of other tumors.

Long-term results of iodine 125 irradiation of uveal melanoma

The authors report on 64 of the first 65 patients treated with iodine 125. The mean follow-up was 64.9 months. After treatment, 29 patients (45.3%) retained visual acuity of 20/100 or better, and 18 patients (28.1%) retained visual acuity within two lines of visual acuity before irradiation. Eleven patients (17.2%) died of metastasis, and 5 patients (7.8%) had local recurrence. Cataract developed in 29 (45.3%) patients; keratitis developed in only 2 (3.1%) patients, and dry eye developed in none. Neovascular glaucoma developed in 7 (10.9%) patients, and 15 (23.4%) patients had radiation retinopathy. Eleven patients (17.2%) required enucleation for either tumor growth or neovascular glaucoma. These results show the increasing number of radiation complications seen with long-term observation and the frequently seen adverse visual outcome.

Improved iodine-125 plaque design in the treatment of choroidal malignant melanoma

The use and development of iodine-125 plaque therapy for choroidal malignant melanoma are described. Since 1975 experience has led to changes in plaque design and insertion techniques. Twenty-one patients were irradiated with local episcleral iodine-125 plaques. Three patients required a second plaque for tumour recurrence. Four eyes were enucleated because of continued tumour growth and a further eye was removed because of glaucoma secondary to radiation retinopathy. Two patients (9.5%) died of metastases. The remaining 19 patients are alive and clinically clear of metastases, with a mean follow up time of 73.1 months (range 43-142 months).

Treatment of juxtapapillary melanomas

Thirty nine patients suffering from juxtapapillary choroidal melanoma were treated with Ru-106/Rh-106 beta-ray plaques. The tumoricidal dose was 100 Gy at the apex of the tumour within 7-14 days. Additional photocoagulation was performed in 12 eyes. The irradiated eyes of three patients had to be enucleated, seven patients died, five of them (12.8%) from metastases. Thirty two (82%) patients are alive and 29 (74%) have a seeing eye. From the whole series 20 (51%) developed flat scars and 11 (29%) patients retained a visual acuity of 0.5-1.0. Radiogenic late complications with damage to the optic nerve and macula were the main causes of visual deterioration.

Management of posterior uveal melanoma

In recent years, there have been a number of advances in the diagnosis and management of patients with malignant melanoma of the posterior uvea (ciliary body and choroid). This review provides a brief update on the current status of diagnostic modalities, such as fluorescein angiography, ultrasonography, computed tomography, magnetic resonance imaging, fine needle aspiration biopsy, and the radioactive phosphorus uptake test. Following that is a more detailed review of the current controversy regarding the natural course of uveal melanomas and the available therapeutic modalities. Current indications, techniques, complications, and results are provided for various forms of management, such as observation, laser photocoagulation, plaque radiotherapy, charged particle radiotherapy, local tumor resection, enucleation, and orbital exenteration.

Histopathology studies in human malignant melanomas of the choroid after unsuccessful treatment with 106Ru/106Rh ophthalmic applicators

Choroidal malignant melanomas were examined after unsuccessful brachytherapy with 106Ru/106Rh ophthalmic plaques. The histologic findings were compared with those obtained in non-irradiated melanomas similar in size and location. Both groups revealed no significant clinical difference apart from the lower average age of the irradiated patients. Some of the histologic features (scar formation, changes in the distribution of cell types, rate of mitosis) represented reactions to irradiation. No single histologic feature was strongly correlated to the irradiated group. The phenomenon of radioinsensitivity observed in some malignant melanomas cannot be fully elucidated using conventional histologic methods.

Dosimetry and physical treatment planning for iodine eye plaque therapy

The dosimetry of eye plaques loaded with iodine-125 seeds (type 6702) was performed by means of computer calculations and measurements with thermoluminescent dosimeters (TLD). Measurements of the depth dose distribution (2-25.5 mm) along the transverse axis of a single seed were performed in water equivalent phantom material. The transverse axis attenuation and geometry factor F(r) was obtained by applying a least squares fit to the measured data. Based on the resulting radial dose function, a computer program was developed which calculates dose distributions within the eye for arbitrary loading and placement of the eye plaque. The computational results were verified by TLD measurements in an eye phantom.

The conservative management of choroidal melanoma

The results of 32 choroidal melanomas managed by observation, Iodine-125 scleral plaques and local surgical excision are presented. Initially, 12 patients were managed by observation, and of these three continued to be managed by observation alone. Fifteen patients were managed with Iodine-125 scleral plaques and followed for an average of 15 months. The tumour regressed in 11, remained the same in three, and recurred in one case. The final visual acuity remained within two Snellen lines of that recorded preoperatively in 10 patients. Fourteen patients underwent local excision with an average follow-up of 31 months. These cases, in general, had larger tumours. The final visual acuity was within two Snellen lines of the preoperative vision in four patients. Five eyes required enucleation at a later date. Four of the five enucleations occurred earlier in the series. The management of choroidal melanoma remains controversial. Various methods of conservative treatment are described and the indications for conservative management by observation, scleral plaque and local excision are discussed.

Experimental study on the fractionation schedule for proton irradiation of uveal melanoma

Greene melanoma in the anterior chamber of rabbits was irradiated by protons to find the isoeffect curve for proton irradiation fractionated into one, two, three or four doses. The isoeffect curve for tumor tissue remained constant between one- and three-dose fractionations and rose with four-dose fractionation. The isoeffect curve for normal tissue approximately followed the Ellis equation. Therefore, the optimal irradiation schedule should be in the range of three fractions because this best spares normal tissue while delivering a tumoricidal dose to the lesion. The relative reduction of the total dose from four- to one-dose fractions of intraoperative irradiation should be 20%.

Magnetic resonance imaging of juxtapapillary plaques in cadaver eyes

Adequate treatment of juxtapapillary melanomas with episcleral plaque brachytherapy using lower energy radiation sources may be difficult because of uncertainties regarding the relationship of the plaque to the optic nerve and tumour base. We obtained magnetic resonance images of a dummy plaque placed in a juxtapapillary location in cadaver specimens. Although it is possible to place a plaque in close association with the optic nerve sheath, a tissue barrier exists which may prevent actual contact between the plaque and nerve. Posterior tilting of the plaque may also occur. Because of these uncertainties regarding plaque placement, juxtapapillary melanomas should be considered a distinct subgroup when evaluating the efficacy of radioactive plaque brachytherapy in the treatment of choroidal melanoma.

Effect of various doses of radiation for uveal melanoma on regression, visual acuity, complications, and survival

We reviewed 284 choroidal and ciliary body melanomas treated with 50, 60, 70, or 80 gray equivalents (GyE) of helium ion radiation. Multivariate methods of data analysis were used to adjust for differences between dose groups with respect to the characteristics of patients (and their tumors). Radiation dose level did not affect survival, complications, visual outcome, or tumor regression in this model. The minimum radiation dose necessary to achieve tumor control with charged particles may be less than 50 GyE.

106Ru/106Rh plaque radiotherapy for malignant melanomas of the choroid. With follow-up results more than 5 years

Therapeutic results are presented with follow-up examinations of at least 5 years (min. 5 years, max. 22 years) after 106Ru/106Rh plaque radiotherapy of posterior uveal melanomas. Out of 227 patients 146 (= 64.3%) could be treated successfully, 37 (= 16.3%) had to be enucleated and are alive, 44 (= 19.4%) died from metastases and 40 (17.6%) from other causes. 75.0% of all small melanomas (T1a) showed an excellent regression pattern to flat scars. Five years after treatment the survival rate was 83.7% (deaths from any causes) respectively 88.2% (deaths from metastases only) and 64.8% (deaths from any causes) respectively 79.7% (deaths from metastases only) ten years after irradiation. 106Ru/106Rh plaque radiotherapy can be recommended for small (T1a, b) and medium sized (T2) choroidal melanomas.

Samarium-145: a new brachytherapy source

A new radiation source has been produced for brachytherapy, with radiation energies slightly above those of 125I, and a T1/2 of 340 d. This source, 145Sm, is produced by neutron irradiation of 144Sm (96.5% enriched). Decay is by electron capture with 140 K x-rays per 100 disintegrations in the energy region between 38-45 keV, plus 13 gamma-rays at 61 keV. These sources are encapsulated in Ti tubes, approximately 0.8 mm X 4.5 mm, and have been developed for temporary implantation in brain and ocular tumours. The 38-61 keV photons should make such sources easy to shield, while providing a dose distribution from source arrays somewhat more homogeneous than that from 125I. In addition, the 340 d half life of 145Sm permits its use for times significantly longer than that of 60 d 125I. While the 145Sm sources have been designed primarily for implantation in a brain tumour, they should be useful for almost any conventional brachytherapy application.

Dose distributions of model 6702 I-125 seeds in water

Dose distributions in water of Model 6702 I-125 seeds have been measured to a distance of 9 cm from the seed center as a function of angle about the seed axis. A silicon diode and electrometer were used in the measurement. Two empirical models have been fitted to the data. The data have also been compared with Monte Carlo calculations.

Clinicopathologic report of successful cobalt 60 plaque therapy for choroidal melanoma

A 66-year-old man had malignant melanoma of the choroid that enlarged during a two-year period while a retinal detachment developed. Treatment consisted of a cobalt 60 plaque placed to deliver a dose of 35,000 rads to the base and 9,000 rads to the apex of the tumor. Clinical response was excellent and complete regression occurred. The patient later died of an unrelated disease. Histopathologic study verified complete regression of the tumor.

Iodine-125 irradiation of choroidal melanoma. Clinical experience

Twenty-nine patients with choroidal melanomas were treated with iodine-125 seeds in gold scleral plaques. Iodine-125 emits low energy 25 KeV photons which are attenuated by the side and back of the plaques so that the radiation is "directed" towards the choroidal tumor. The anticipated therapeutic benefits of using a low energy isotope and directional applicators have been realized. There has been a marked reduction in ocular complications in the nine medium and 20 large melanomas so treated. Our complication rate was 34% with a mean follow-up of 38 months. This is a lower complication rate, with longer follow-up, and in larger tumors than that reported with the use of cobalt-60, ruthenium-106 or ion beam. Three patients with large tumors and two patients with medium tumors died of metastasis. This compares favorably to results of similarly sized melanomas treated by enucleation.

New radiotherapeutic techniques in nuclear ophthalmology

Various aspects of radiotherapeutic techniques used in treating ocular tumors are discussed. Previous and current "standard" modalities are briefly reviewed, including beta and gamma emitters, 60Co, 125I, and charged particles. In particular, emphasis is placed upon techniques under development that use biomolecules to physiologically target radioactive or stable isotopes to ocular melanoma. These procedures include 35S-thiouracil, 127I-deoxyuridine in conjunction with irradiation with photons from 145Sm, neutron capture therapy, and various combinations of the above. Thiouracil shows particular promise because of its incorporation during malanin synthesis in growing melanoma. Radiosensitization and stimulation of Auger cascades via introduction of iodine in DNA followed by irradiation with activating photons of appropriate energy (from 145Sm) has been shown to be effective in vitro. Various molecules may be used to transport boron to ocular melanoma, including thiouracil, thus allowing selective irradiation of tumor cells via 10B (n, alpha) 7Li reaction.

Radioactive phosphorus uptake test for the diagnosis of malignant melanoma of the choroid

The most frequently used radioisotope in ophthalmology is radioactive phosphorus (32P). Since its introduction into ophthalmology in 1951, it has been used primarily as an aid in the diagnosis of malignant melanoma of the choroid. During the thirty years of clinical use, the indications for this test have been clearly defined. The maximum tissue penetration of 32P is 7 mm. Surgical dissection is therefore frequently necessary to enable the ophthalmologist to place the Geiger-Muller probe on the sclera in proximity to the tumor. False positive and false negative results are unusual and the test is between 96% and 100% accurate.

Tumor detection with radiopharmaceuticals

The most common primary ocular tumor in adults is malignant melanoma of the choroid. Metastatic tumors to the choroid occur with the same frequency. The radioactive phosphorous uptake test is used most often as a nuclear diagnostic test. The test does not differentiate melanomas from metastases, and it is necessary to perform surgery for proper placement of a detection device within a distance of 1-2 mm of the tumor. These deficiencies leave ophthalmologists with a pressing need for a gamma-emitting radiopharmaceutical that would facilitate noninvasive identification of choroidal melanoma. This need is made more urgent by the fact that recently, radiation therapy has been used to treat these tumors rather than enucleation. Eyes then harbor irradiated melanoma whose status is unknown. The tumor rarely decreases in size more than 25% to 50%. There is thus a need for a specific diagnostic test to assess the nature of the tumor and the effectiveness of therapy.

Hematoporphyrin derivative photoradiation induced damage to normal and tumor tissue of the pigmented rabbit eye

Cytotoxicity induced by hematoporphyrin derivative (HpD) photoradiation in both normal and experimental tumor tissue of pigmented rabbit eyes has been examined. In addition, documentation of HpD induced fluorescence in ocular structures has also been obtained. Acute normal ocular tissue toxicity studies demonstrated that HpD (1-10 mg HpD/kg) followed 48 hours later by a transpupil irradiation of red light (635 nm, 36-90 J/cm2) resulted in demarcated areas of retinal damage. Long term (chronic) toxicity studies have shown that the initial damage to the retina was permanent but that no damage to the cornea, lens or vitreous could be observed during a 16 month follow-up. Visual and histological documentation have been obtained, following HpD photoradiation therapy (PRT), in rabbit eyes having heterotransplanted single nodule amelanotic melanomas. A toxic effect characterized by tumor blanching, edema and hemorrhage was observed within 24 hours of treatment. Histological examination obtained 24 hours following HpD PRT illustrated massive tumor tissue necrosis and vascular disruption. HpD PRT at clinically relevant doses was also shown to be effective in selectively curing the highly malignant amelanotic iris melanoma. It is concluded that HpD PRT may prove to be an effective modality for treating certain ocular tumors.