Posttreatment visual acuity in patients treated with episcleral plaque therapy for choroidal melanomas: dose and dose rate effects.
OBJECTIVE
To determine the relationship between the long-term visual function and the dose and dose rates delivered to critical ocular structures in patients with choroidal melanoma treated with 125I episcleral plaque radiotherapy.


METHODS
From 1987 to 1994, 63 patients underwent 125I episcleral plaque (Collaborative Ocular Melanoma Study [COMS] design) application for the treatment of choroidal melanoma. The mean tumor height was 4.5 mm (range 1.7-8.3). Doses and dose rates at the tumor apex, macula, and optic disc were calculated. Forty-three records were scored to assess whether a decrease in visual acuity of >2 lines on a standard Snellen eye chart had occurred. Patient age and the presence of hypertension or diabetes were noted. Statistical analysis was performed to assess both the rate at which visual decline had occurred and the presence of significant factors that had contributed to this decline.


RESULTS
With a median follow-up of 36 months, the 3-year actuarial survival rate was 93.6%. The 3-year actuarial local control rate was 86.9%. The median time to visual loss after therapy was 18.7 months. The 3-year actuarial rate of visual preservation was 40.5%. Multivariate analysis demonstrated higher macula dose rates (p = 0.003) to forecast visual decline. Macula dose rates of 111 +/- 11.1 cGy/h were associated with a 50% risk of significant visual loss.


CONCLUSIONS
Patients in our series treated with 125I plaque brachytherapy for choroidal melanoma experienced favorable tumor control, but with a measurable incidence of visual decline. Higher dose rates to the macula correlated strongly with poorer posttreatment visual outcome. This information may be valuable in selecting the optimal dose rates to treat choroidal melanomas and to predict the risk of visual decline.
Jones
Robert
R
Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA. drrjones@hotmail.com
Gore
Elizabeth
E
Mieler
William
W
Murray
Kevin
K
Gillin
Michael
M
Albano
Katherine
K
Erickson
Beth
B
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001918:Brachytherapy / Q000379:methods; D002830:Choroid Neoplasms / Q000401:mortality / Q000503:physiopathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage / Q000627:therapeutic use*; D008266:Macula Lutea / Q000528:radiation effects; D008297:Male; D008545:Melanoma / Q000401:mortality / Q000503:physiopathology / Q000532:radiotherapy*; D008875:Middle Aged; D009898:Optic Disk / Q000528:radiation effects; D015996:Survival Rate; D014786:Vision Disorders / Q000209:etiology; D014792:Visual Acuity
D007457:Iodine Radioisotopes