Uveal Melanoma Treated With Iodine-125 Episcleral Plaque: An Analysis of Dose on Disease Control and Visual Outcomes

Abstract

PURPOSE In the treatment of uveal melanomas, the optimal prescribed dose to maximize disease control, but minimize radiation-related complications is unknown. Historically our institution has treated uveal melanomas to doses less than 85 Gy to the tumor apex even if the apex was less than 5mm in height. Here, we investigate how tumor control and visual outcomes are affected by the radiation dose at the tumor apex. METHODS AND MATERIALS A retrospective review was performed to evaluate patients treated for uveal melanoma with Iodine-125 plaques between 1988 and 2010. Radiation dose is reported as dose to tumor apex and dose to 5 mm. Primary end points included time to local failure, distant failure, and death. Secondary end points included eye preservation, visual acuity, and radiation-related complications. Univariate and multivariate analyses were performed to determine association between radiation dose and the end point variables. RESULTS One hundred ninety patients with sufficient data to evaluate the end points were included. The 5 year local control (LC) rate was 91%. The 5 year distant metastases (DM) rate was 10%. The 5 year overall survival (OS) rate was 84%. There were no differences in outcome (LC, DM, OS) when dose was stratified by apex dose quartile (<69 Gy, 69–81 Gy, 81–89 Gy, >89 Gy). However, increasing apex dose and dose to 5 mm depth were correlated with greater visual acuity loss (p=0.02, p=0.0006), worse final visual acuity (p=0.02, p<0.0001) and radiation complications (p<0.0001, p=0.0009). In addition, enucleation rates were worse with increasing quartiles of dose to 5 mm (p=0.0001). CONCLUSIONS Doses at least as low as 69 Gy prescribed to the tumor apex achieve rates of local control, distant metastasis free survival, and overall survival that are similar to radiation doses of 85 Gy to the tumor apex, but with improved visual outcomes.

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

“…The latter study suggested that dose to the true apical height may render a lower incidence of radiation-related complications. In another retrospective case study of 190 patients, Perez et al [15] showed data stratified by varied dose quartiles (<65.0 to >85.0 Gy) and reported no association between dose to tumor apex and rate of local failure (9%), which was similar to the COMS trial despite having significantly reduced doses in 50% of their patients. By stratifying their treatment groups to different dose quartiles, they also found a direct relationship between radiation dose and ocular toxicity.…”

“…Fourteen studies were retrospective clinical chart reviews [14,15,22,23,24,25,26,27,28,29,30,31,32], and 1 was a prospective, randomized trial, the COMS trial [17]. One retrospective study included patients from the COMS trial [15].…”

“…This dose was adjusted (originally 100.0 Gy) after the Task Group (TG 43) protocol was adopted by the American Association of Physicists in Medicine [12]. The dose of 85.0 Gy for the COMS trial was selected based upon expert consensus [9,11,13,14,15]. The COMS study showed that an eye-preserving, and potentially a vision-preserving, therapeutic regimen with iodine-125 plaque brachytherapy had a non-inferior mortality risk compared to enucleation up to 12 years following treatment [16].…”

Prescribing to tumor apex in episcleral plaque iodine-125 brachytherapy for medium-sized choroidal melanoma: A single-institutional retrospective review

“…The change in prescription point from 5-mm point to tumor apex for tumors ! 5 mm thick allows for the reduction of dose to sensitive (18) in which the same approach as prescribing to the apex of tumor was used. Local tumor control at 5 years was 91% comparable to COMS data.…”

“…The plaque covered the largest basal dimension of tumor with a radial margin of 2e3 mm. The plaque size was determined for each individual patient as one of following six available plaques: 10,12,14,16,18, and 20 mm. The number of seeds corresponding to each plaque was 5,8,13,13,21, and 24, respectively.…”