Cobalt-60 Plaque Radiotherapy Research Articles

Orbital Melanoma Metastatic From Contralateral Choroid: Management by Complete Surgical Resection

We discuss a clinicopathologic correlation of orbital metastasis from a contralateral choroidal melanoma wherein the orbital tumor was removed completely by surgical resection. In October 1982, a 29-year-old woman was treated with cobalt-60 plaque radiotherapy for a choroidal melanoma in her right eye. The tumor responded well but recurred after 9 years, necessitating enucleation. In August 1999, 17 years after initial presentation, metastatic melanoma to liver, lung, and brain were found and the patient had a favorable response to chemotherapy and brain irradiation. Five months later, in November 2000, an enlarging orbital mass was documented to be compressing the left optic nerve. Complete surgical removal of the tumor was achieved by a superotemporal orbitotomy. Histopathologically, the tumor was a malignant melanoma with features similar to the choroidal tumor. The contralateral orbit can be the site of late metastasis from choroidal melanoma. In rare instances, an orbital metastasis can be completely removed surgically without subjecting the patient to orbital irradiation.

Combined iodine-125 plaque irradiation and indirect ophthalmoscope laser therapy of choroidal malignant melanomas: Comparison with iodine-125 and cobalt-60 plaque radiotherapy alone

The authors studied the short-term impact of combined episcleral iodine-125 plaque radiotherapy and argon laser treatment in a series of 24 patients with choroidal malignant melanoma. All patients underwent plaque therapy prior to their initial laser session. All laser treatments were performed with an indirect ophthalmoscope argon green laser, using low-power, long-duration exposures. The endpoint of laser therapy was a well-defined atrophic circumbasal chorioretinal laser scar and complete or nearly complete nonfluorescence of the lesion on fluorescein angiography. In a case-by-case matched comparison study, the authors evaluated the relative local regression of tumors treated by combined plaque-laser therapy, iodine-125 plaque therapy alone, and cobalt-60 plaque therapy alone. The tumors treated with supplemental laser regressed substantially faster and more completely than did those treated by either type of plaque therapy alone. However, the short-term visual loss was greater in eyes treated by the combined therapy.

Cataractogenesis after cobalt-60 eye plaque radiotherapy

Purpose : This study was designed to estimate the actuarial incidence of typical postirradiation cataracts and to identify prognostic factors related to their development in melanoma-containing eyes treated by Cobalt-60 plaque radiotherapy. Our special interest was the impact of calculated radiation dose and dose-rate to the lens. Methods and Material : The authors evaluated the actuarial occurrence of post-irradiation cataract in 365 patients with primary posterior uveal melanoma treated by Cobalt-60 plaque radiotherapy between 1976 and 1986. Results : Only 22% (S.E. = 4.6%) of the patients who received a total dose of 6 to 20 Gy at the center of the lens developed a visually significant cataract attributable to the radiation within 5 years after treatment. Using multivariate Cox proportional hazards modeling, the authors identified thickness of the tumor, location of the tumor's anterior margin relative to the equator and the ora serrata, and diameter of the eye plaque used as the best combination of covariables for predicting length of time until development of cataract. Surprisingly, the dose of radiation delivered to the lens, which was strongly correlated to all of these covariables, was not a significant predictive factor in multivariate analysis. Conclusion : The results suggest that success of efforts to decrease the occurrence rate of post-irradiation cataracts by better treatment planning might be limited in patients with posterior uveal melanoma.

Matched Group Study of Surgical Resection Versus Cobalt-60 Plaque Radiotherapy for Primary Choroidal or Ciliary Body Melanoma

We report the results of a nonrandomized, matched-group, survival and visual preservation study of patients with a choroidal or ciliary body melanoma managed by microsurgical resection of the tumor versus cobalt-60 episcleral plaque radiotherapy. Each treatment group consisted of 30 patients. All patients were matched on a case-by-case basis in terms of tumor size (largest linear tumor dimension), location of the anterior tumor margin relative to the ora serrata, location of the posterior tumor margin relative to the equator, and age at the time of treatment. Although the estimated actuarial 5-year survival probability was slightly greater in the resection group (85.2%) than in the cobalt plaque group (81.8%), this difference was neither clinically impressive nor statistically significant. In contrast, there was a substantially higher rate of early posttreatment severe visual loss in the resection group (P = .0008, Mantel-Haenszel test).

Cobalt-60 Plaque Radiotherapy vs Enucleation for Posterior Uveal Melanoma

We compared the survival of 302 patients with a primary choroidal or ciliary body melanoma treated by cobalt-60 plaque radiotherapy between 1976 and 1982 with the survival of 134 patients treated by enucleation during the same period. Tumor size, location of the anterior margin of the tumor, and patient age at the time of treatment were identified as simultaneous significant clinical variables for predicting melanoma-specific mortality by multivariate Cox proportional hazards modeling. We computed a prognostic index for each patient based on this model and found that patients in the enucleation group had slightly higher values of this index than did patients in the cobalt-60 plaque radiotherapy group. Risk ratios for the treatment effect computed from a Cox model incorporating prognostic index and the treatment variable were found to be approximately equal to 1, both for analysis of melanoma-specific mortality and total mortality. These results indicate that when one controls for differences in prognostic index between the groups, cobalt-60 plaque therapy and enucleation are essentially equivalent in their effect on survival.

Post-irradiation Regression of Choroidal Melanomas as a Risk Factor for Death from Metastatic Disease

To determine the prognostic value of the regression rate of choroidal melanomas after cobalt-60 plaque radiotherapy, the authors performed a multivariate analysis on 159 patients treated with a cobalt plaque during the interval from 1976 through 1980. Thirty-three of the 159 patients had died as of the survey date; 29 of metastatic melanoma and 4 of other causes. Multivariate Cox proportional hazards modeling identified a two-term regression incorporating maximal basal tumor diameter at treatment and tumor thickness at 12 months posttreatment as the best model (P < 0.005 for both parameters) for predicting length of tumor-free survival. These results are consistent with the hypothesis that rapid regression of a choroidal melanoma after cobalt-60 plaque radiotherapy is an unfavorable prognostic sign for prolonged metastasis-free survival.

Panretinal Photocoagulation for Radiation-Induced Ocular Ischemia

We present preliminary findings on the effectiveness of panretinal photocoagulation in preventing neovascular glaucoma in eyes with radiation-induced ocular ischemia. Our study group consisted of 20 patients who developed radiation-induced ocular ischemia following cobalt-60 plaque radiotherapy for a choroidal or ciliary body melanoma. Eleven of the 20 patients were treated by panretinal photocoagulation shortly after the diagnosis of ocular ischemia, but nine patients were left untreated. In this non-randomized study, the rate of development of neovascular glaucoma was significantly lower (p = 0.024) for the 11 photocoagulated patients than for the nine who were left untreated.

Regression of posterior uveal malignant melanomas after cobalt plaque radiotherapy.

We reviewed the records of 17 patients with posterior uveal malignant melanoma who had been followed for at least 3 months prior to cobalt plaque radiotherapy and whose tumor had been documented to enlarge in thickness during that interval. We evaluated the relationship between the rates of pretreatment tumor enlargement and post-treatment tumor shrinkage using linear regression analysis. We found that the rate of postirradiation tumor shrinkage correlated strongly with the rate of preirradiation tumor enlargement regardless of whether the pretreatment rate of growth was slow, intermediate or rapid. We speculate that the more rapidly regressing tumors were more mitotically active than their more slowly regressing counterparts. If true, the survival rate of patients whose posterior uveal malignant melanomas regress rapidly following radiation therapy may prove to be worse than that of patients whose tumors regress slowly.

Cataract Surgery Following Cobalt 60 Plaque Radiotherapy for Posterior Uveal Malignant Melanoma

We reviewed the records of thirteen patients with posterior uveal malignant melanoma who had developed a mature radiation cataract following cobalt-60 plaque radiotherapy. Cataract extraction had been performed in seven of these patients as of the survey date of this investigation. We attempted to determine if cataract extraction increased the risk of metastatic melanoma, improved or worsened visual function, or resulted in any consistent intraoperative or postoperative complications that did not occur if the cataract was retained. Our analysis showed that removing the cataract did not appear to increase the risk of death from metastatic melanoma, but it also indicated that cataract extraction did not seem to improve the visual function of the irradiated eye. On the basis of our experience to date, we offer suggested guidelines for the management of patients who develop a mature cataract following cobalt-60 plaque radiotherapy of a posterior uveal malignant melanoma.

Metastatic uveal melanoma. Pretherapy serum liver enzyme and liver scan abnormalities.

The liver was the organ most frequently involved in 50 patients with primary melanomas of the choroid or ciliary body, who were treated with enucleation or cobalt plaque radiotherapy and who subsequently developed systemic metastasis. Forty-seven (94%) of the patients had clinical or laboratory evidence of liver metastasis. The median survival time following treatment of the primary choroidal melanoma was 28 months (range, 7.7 to 123.1 months). Results of pretreatment studies, including serum liver enzyme levels, liver scans, or both, were abnormal in six (12%) of the patients studied. As a group, the eight patients who died within one year following ocular surgery had a significantly higher prevalence of pretreatment laboratory abnormalities. Extraocular extension of the choroidal melanoma was also present in four (50%) of these eight patients. Conversely, no patient who survived longer than the median survival period (28 months) had abnormal pretreatment laboratory findings.

Regression of Posterior Uveal Melanomas Following Cobalt-60 Plaque Radiotherapy

AbstractA method has been devised for evaluating the rate and extent of regression of the first 100 consecutive patients with a posterior uveal melanoma that we had managed by Cobalt-60 plaque radiotherapy at Wills Eye Hospital. It was found that the "average" posterior uveal melanoma in the series did not regress rapidly to a flat, depigmented scar but shrank slowly and persisted as a residual mass approximately 50% of the thickness of the original tumor at 54 months following Cobalt-60 plaque radiotherapy. We also found that the rate and extent of regression of the tumors in patients who subsequently developed metastatic melanoma were not appreciably different than the rate and extent of regression of the tumors in patients who remained well systemically. These observations indicate that the rate and extent of regression of posterior uveal melanomas following Cobalt-60 plaque radiotherapy are poor indicators of the prognosis of the affected patients for subsequent development of clinical metastatic disease.

Thymus-derived lymphocyte enumeration in patients with uveal malignant melanoma.

Thymus-derived lymphocytes (T lymphocytes) were enumerated in patients with uveal malignant melanoma. Two T-lymphocyte subpopulations were determined, the active rosette forming cells (A-RFC) and the total rosette forming cells (T-RFC). Subjects were divided into the following groups: (a) pretreatment patients, (b) patients treated by enucleation, (c) patients treated by photocoagulation, (d) patients treated by cobalt plaque radiotherapy, (e) patients treated by enucleation who developed clinically detectable metastasis, and (f) normal controls. There were no differences in the numbers of A-RFC or T-RFC in the control population, pretreatment patients, and those treated in the different ways. Statistically significant depressions of A-RFC and T-RFC levels were seen in patients with metastatic lesions, suggesting that they had an impairment of immunocompetence, as measured by T-lymphocyte rosette formation.

Visual Results Following Cobalt Plaque Radiotherapy for Posterior Uveal Melanomas

Visual results of cobalt plaque radiotherapy on the eyes of 77 patients with posterior uveal melanoma in one eye and pretreatment visual acuity of 20/25 or better in both eyes were analyzed using actuarial methods. The study demonstrated that eyes receiving a radiation dose in excess of 5,000 rad to the fovea and/or optic disc commonly lose a substantial amount of vision within 2 to 3 years. It also showed that eyes treated by cobalt plaque radiotherapy for a large posterior uveal melanoma are more likely to suffer profound visual loss than those treated for a medium or small melanoma. The predominant cause of severe visual loss in these patients appeared to be foveal radiation retinopathy.

Cobalt Plaque Therapy of Posterior Uveal Melanomas

One hundred patients with choroidal melanomas who were treated by the authors with cobalt plaque radiotherapy were analyzed with regard to tumor regression, visual results, complications, and mortality rate. The follow-up period at the time of this writing ranged from one to five years. These preliminary observations indicate that cobalt plaque radiotherapy induces tumor regression in 96% of cases, preserves useful vision in many cases and has fewer complications during the one- to five-year follow-up period than previously believed.