I-125 PLAQUE THERAPY FOR UVEAL MELANOMA - ANALYSIS OF THE IMPACT OF TIME AND DOSE FACTORS ON LOCAL-CONTROL

BACKGROUND. I-125 episcleral plaque therapy has gained wide acceptance for the treatment of uveal melanoma because of its potential to prese rve vision, salvage the globe, and provide good local control. A rigor ous analysis of the optimum radiation dose, dose rate, and overall tre atment time has not been reported with this technique. METHODS. One hu ndred fifty patients with uveal melanoma treated with I-125 plaques be tween 1982 and 1990 and included in the uveal melanoma study (UMS) dat abase of the Wills Eye Hospital were analyzed. Mean patient age was 60 .7 years (range: 17.7-84.6 years). Initial mean tumor size was 9.7 x 8 .5 x 3.7 mm with a range of 4.5 to 21.5 mm in basal dimension and 1.2 to 11.8 mm in height. Mean dose to the tumor apex was 94.77 gray (Gy) (29.5-141 Gy). Mean dose rate to the tumor apex was 92.9 cGy/hr (10-29 2 cGy/hr); the mean dose to the base was 359 Gy (181-692 Gy); the mean dose rare to the base was 348 cGy/hr (112-893 cGy/hr); and mean durat ion of treatment was 124.7 hours (range: 28-333 hours). RESULTS. With a median follow-up of 68 months, there have been 33 local failures. Me an time to local failure was 19 months (range: 6-78 months). Actuarial local central is 81% at 5 years. Multivariate analysis demonstrates s ignificant correlation of local failure with larger tumor dimension (P = 0.0046), close proximity to the optic disc (P = 0.0029), lower radi ation dose to the tumor apex (P = 0.03), lower radiation dose rate to the tumor apex and base (P = 0.01 and 0.03), and longer overall treatm ent time (P = <0.0001). CONCLUSIONS. This retrospective analysis reinf orces the importance of dose rate, minimum tumor dose, overall treatme nt time, maximum tumor basal dimension, and proximity to the optic ner ve in the treatment of uveal melanoma. (C) 1996 American Cancer Societ y.