[Plaque radiotherapy for anterior uveal melanomas]

High-Dose-Rate Yttrium-90 (90Y) Episcleral Plaque Brachytherapy for Iris and Iridociliary Melanoma

Purpose

To describe a pilot study on the use of single-session, high-dose-rate, Food and Drug Administration-cleared, yttrium-90 (Y90) plaque brachytherapy for iris and iridociliary melanoma.

Design

A single-center, clinical case series.

Participants

Six consecutive patients were included in this study. Each was diagnosed with an iris or iridociliary melanoma based on clinical examination with or without biopsy.

Methods

Each tumor was staged according to the American Joint Committee on Cancer criteria and received Y90 eye plaque brachytherapy. The main variables were tumor size, patient age, sex, and method of diagnosis (clinical or biopsy). Surgical techniques, treatment durations, and ocular side effects were recorded. Local control was defined as a lack of tumor growth or regression determined by clinical examinations, including slit-lamp and gonio photography, as well as high-frequency ultrasound measurements. Toxicity parameters included acute and short-term corneal/scleral change, anterior segment inflammation, and cataract progression.

Main Outcome Measures

Local and systemic cancer control, tumor regression, visual acuity, as well as radiation-related normal tissue toxicity.

Results

High-dose-rate Y90 plaque brachytherapy was used to treat small (American Joint Committee on Cancer cT1) category melanomas. Single-surgery high-dose-rate irradiations were performed under anesthesia. Because of short treatment durations, high-dose-rate Y90 did not require the additional procedures used for low-dose-rate plaque (e.g., sutures, amniotic membrane epicorneal buffering, Gunderson flaps, and second surgeries for plaque removal). Only conjunctival recession was used to avoid normal tissue irradiation. High-dose-rate Y90 treatment durations averaged 8.8 minutes (median, 7.9; range, 5.8-12.9). High-dose-rate Y90 brachytherapy was associated with no periorbital, corneal (Descemet folds), or conjunctival edema. There was no acute or short-term anterior uveitis, secondary cataract, scleropathy, radiation retinopathy, maculopathy, or optic neuropathy. The follow-up was a mean of 16.0 (range 12-24) months. Evidence of local control included a lack of expansion of tumor borders (n = 6, 100%), darkening with or without atrophy of the tumor surface (n = 5/6, 83%), and a mean 24.5% reduction in ultrasonographically measured tumor thickness. There were no cases of metastatic disease.

Conclusions

High-dose-rate Y90 brachytherapy allowed for single-surgery, minimally invasive, outpatient irradiation of iris and iridociliary melanomas.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Yttrium-90 Episcleral Plaque Brachytherapy for Choroidal Melanoma

Purpose: To describe the first use of high-dose-rate yttrium-90 disc brachytherapy for choroidal melanoma. Methods: A 72-year-old patient had a cT1-category choroidal melanoma characterized by the presence of orange pigment, increasing subretinal fluid (SRF), and enlarging tumor thickness. It was treated with single-session, light-guided, light-defined yttrium-90-disc brachytherapy. Results: A specialized handheld applicator provided with 4 encircling lights was used to guide plaque placement and localize treatment. Unlike low-dose-rate plaques, high-dose-rate yttrium-90 required only 3 minutes 39 seconds. In this case, treatment did not require episcleral sutures, muscle relocation, outpatient dwell time, or a second surgery. High-dose-rate treatment improved radiation safety by eliminating perioperative exposure to health care personnel, the community, and the family. At the 13-month follow-up, the SRF and tumor thickness were diminished. There was no secondary cataract, radiation retinopathy, maculopathy, or optic neuropathy, and the visual acuity was 20/20. Conclusions: Yttrium-90 brachytherapy allowed for single-surgery, minimally invasive, outpatient irradiation of a choroidal melanoma.

First clinical implementation of Yttrium-90 Disc Brachytherapy after FDA clearance

PURPOSE

Herein, we study if high-dose-rate (HDR) yttrium-90 (⁹⁰Y) brachytherapy could be utilized by medical physicists, radiation oncologists, and ophthalmic surgeons.

METHODS AND MATERIALS

Yttrium-90 (⁹⁰Y) beta-emitting brachytherapy sources received United States Food and Drug Administration clearance for episcleral treatment of ocular tumors and benign growths. Dose calibration traceable to the National Institute of Standards and Technology as well as treatment planning and target delineation methods were established. Single-use systems included a ⁹⁰Y-disc affixed within specialized, multifunction, handheld applicator. Low-dose-rate to high-dose-rate prescription conversions and depth-dose determinations were performed. Radiation safety was evaluated based on live exposure rates during assembly and surgeries. Clinical data for radiation safety, treatment tolerability, and local control was collected.

RESULTS

Practice parameters for the medical physicist, radiation oncologist, and ophthalmic surgeon were defined. Device sterilizations, calibrations, assemblies, surgical methods, and disposals were reproducible and effective. Treated tumors included iris melanoma, iridociliary melanoma, choroidal melanoma, and a locally invasive squamous carcinoma. Mean calculated ⁹⁰Y disc activity was 14.33 mCi (range 8.8-16.6), prescription dose 27.8 Gy (range 22-30), delivered to depth of 2.3 mm (range 1.6-2.6), at treatment durations of 420 s (7.0 min, range 219 s-773 s). Both insertion and removal were performed during one surgical session. After surgery, each disc-applicator- system was contained for decay in storage. Treatments were well-tolerated.

CONCLUSIONS

HDR ⁹⁰Y episcleral brachytherapy devices were created, implementation methods developed, and treatments performed on 6 patients. Treatments were single-surgery, rapid, and well-tolerated with short-term follow up.

Palladium-103 plaque therapy for multifocal iris melanoma: Radiation of the entire anterior segment of the eye

PURPOSE

To investigate the safety and tolerability of total anterior segment palladium-103 (¹⁰³Pd) eye plaque brachytherapy for multifocal iris melanoma.

METHODS

Interventional case series of 11 patients with multifocal iris melanomas. Anterior segment ultrasound revealed tumor size, location, and intraocular margins. Epicorneal amniotic membrane grafts protected the cornea and decreased pain during total anterior segment 103-Pd ophthalmic plaque brachytherapy.

RESULTS

Eleven diffuse iris melanomas were American Joint Committee on Cancer 8th edition-classified as T1 (n = 5, 45.5%) and T2 (n = 6, 54.5%). Plaque radiation was completed to a minimum mean tumor dose of 85 Gy (mean dose rate, 58.1 cGy/h). Ultrasonographic tumor thickness regression was 41% (follow up mean 58.7, median 50, range: 8-139 months). Despite 100% local control and 100% eye retention, one patient (9.1%) developed metastatic disease. Four eyes required cataract surgery. There was no corneal stem-cell deficiency, corneal opacity, radiation maculopathy, or optic neuropathy. While visual acuity prior to treatment was 20/40 or better in 10 (91%), 9 were 20/40 or better (81.9%) at last follow-up. Four (36%) had glaucoma prior to treatment and three eyes developed glaucoma after treatment for a total of 63%.

CONCLUSION

Total anterior segment (¹⁰³Pd) plaque brachytherapy resulted in local control, good visual acuity, eye and life preservation in the treatment of multifocal iris melanoma.

Corneal Substructure Dosimetry Predicts Corneal Toxicity in Patients With Uveal Melanoma Treated With Proton Beam Therapy

PURPOSE

This study examines the relationship between dose to corneal substructures and incidence of corneal toxicity within 6 months of proton beam therapy (PBT) for uveal melanoma. We aim to develop clinically meaningful dose constraints that can be used to mitigate corneal toxicity.

METHODS AND MATERIALS

Ninety-two patients were treated with PBT between 2015 and 2017 and evaluated for grade 2+ (GR2+) intervention-requiring corneal toxicity in our prospectively maintained database. Most patients were treated with 50 Gy (relative biological effectiveness [RBE]) in 5 fractions, and all had complete six-month follow-up. Analyses included Mann-Whitney, χ², Fisher exact, and receiver operating curve tests to identify risk factors for GR2+ toxicity. Bivariate logistic regression was used to identify independent dose-volume histogram (DVH) predictors of toxicity after adjustment for the most important clinical risk factor.

RESULTS

The 6-month PBT GR2+ corneal toxicity rate was 10.9%, with half of patients experiencing grade 2 toxicity and half experiencing grade 3 toxicity, with no grade 4 events. Patients with anterior chamber tumors had a higher risk (58.3%) for toxicity than those with posterior tumors (0%) or posterior tumors extending past the equator (25%, P < .0001). On univariate analysis, larger size according to Collaborative Ocular Melanoma Studies was associated with increased toxicity rate (P < .004). DVH analysis revealed that cutoffs of 58% for V25, 32% for V45, 51.8 Gy (RBE) for maximum dose, and 32 Gy (RBE) for mean dose to the cornea separated patients into groups experiencing and not experiencing toxicity with 90% sensitivity and ≥96% specificity. Bivariate logistic regression indicated that corneal V25, V45, and mean dose independently predicted for toxicity after adjusting for tumor location.

CONCLUSIONS

Patients receiving PBT for anterior uveal melanomas experience a high rate of GR2+ corneal toxicity because of increased corneal dose. Anterior location and corneal DVH parameters independently predict toxicity risk. We propose dosimetric constraints to facilitate treatment planning and toxicity mitigation.