Visual acuity after Ruthenium106 brachytherapy of choroidal melanomas

Eccentric ruthenium plaque radiotherapy of posterior choroidal melanoma

BACKGROUND

The aim of this work is to report on conservation of visual acuity after eccentric ruthenium(106) (Ru-106) brachytherapy of posterior choroidal melanoma.

METHODS

Fifty-four patients with choroidal melanoma extending to within 5 mm of the optic disc or fovea were treated at a single institution during the 3 years up to July 31, 2007. The plaque was positioned eccentrically with its posterior edge aligned with the posterior tumor margin to reduce the radiation dose to the optic disc and fovea. The main outcome measures were local tumor control and conservation of vision of 6/12 or better, according to baseline variables.

RESULTS

The tumors had a mean longest basal diameter of 12.0 mm and a mean thickness of 3.1 mm. The posterior tumor margin extended to within 3 mm of the fovea in 30 patients (56%). In the 24 eyes with the posterior tumor margin located 3.1-5.0 mm from the fovea, 74.9% retained visual acuity of 6/12 or better 4 years after treatment (95% confidence interval [CI], 55.5-94.3%). In the 30 eyes with tumor extension to within 3.0 mm of the fovea, then 3 years after treatment only 25.3% retained such vision (95% CI, 5.3-45.3%). Recurrence at the posterior tumor margin occurred in two patients.

CONCLUSIONS

Eccentric ruthenium(106) plaque radiotherapy of posterior choroidal melanoma achieves good rates of local tumor control and conservation of vision if special measures are taken to ensure that the plaque is positioned correctly.

Dosimetric comparison of 106Ru and 125I plaques for treatment of shallow (<or=5 mm) choroidal melanoma lesions

The aim of this study was to compare dosimetric parameters between iodine-125 ((125)I) and ruthenium-106 ((106)Ru) plaques of similar sizes in the treatment of choroidal melanomas. The study design included retrospective double planning of each case. 26 consecutive patients with choroidal melanomas measuring 5 mm or less in thickness were included. Dose distributions were calculated using Plaque Simulator treatment-planning software for a prescription of 85 Gy to the tumour apex. Doses to the outer sclera, lens, fovea and optic disc were obtained for each case using appropriately sized plaques of each isotope. Statistical inferences were made using the non-parametric Wilcoxon signed rank test. The mean dose to the macula, disc and lens was 18%, 53% and 89% less, respectively, with (106)Ru than with (125)I. Scleral doses were greater for (106)Ru. The use of collaborative ocular melanoma study dosimetry results in even higher mean doses to the macula, disc, lens and sclera. Two-dimensional dose distributions and dose volume histograms demonstrated the increase in dose outside the tumour volume using (125)I. This comparison shows that, for tumours not exceeding 5 mm in thickness, the use of (106)Ru plaques has the potential to reduce the radiation dose to nearby normal structures and possibly lower the risk of radiation-induced visual loss.

Local tumor control after 106Ru brachytherapy of choroidal melanoma

PURPOSE

To report on local tumor control after (106)Ru brachytherapy for choroidal melanoma.

METHODS AND MATERIALS

A total of 458 patients with choroidal melanoma were treated at a single institution between January 1993 and December 2001. The tumors had a median longest basal dimension of 10.6 mm and a median height of 3.2 mm. The brachytherapy was administered using a 15- or 20-mm plaque. For posterior tumors, the plaque was positioned eccentrically with its posterior edge aligned with the posterior tumor margin to reduce the radiation dose to the optic disk and fovea. A minimal scleral dose sufficient to cause visible choroidal atrophy provided a permanent ophthalmoscopic record of the distribution of choroidal irradiation. If radiotherapy to the posterior tumor was uncertain, adjunctive transpupillary thermotherapy was administered 6 months postoperatively.

RESULTS

The actuarial rates of tumor recurrence were 1%, 2%, and 3% at 2, 5, and 7 years, respectively. Local tumor recurrence correlated with the longest basal tumor dimension (Cox univariate analysis, p = 0.02, risk ratio 1.41, 95% confidence interval 1.06-1.88). Seven of the nine eyes with recurrent tumor were salvaged with additional conservative therapy.

CONCLUSION

The low rate of local tumor recurrence suggests that ruthenium plaque radiotherapy is effective with good case selection and if special measures are taken to ensure that the plaque is positioned correctly.