A systematic comparison of dose distributions delivered in iodine-125 plaque brachytherapy and proton radiation therapy for ocular melanoma

Citation:

Trofimov AV, Aronow ME, Gragoudas ES, Keane FK, Kim IK, Shih HA, Bhagwat MS. A systematic comparison of dose distributions delivered in iodine-125 plaque brachytherapy and proton radiation therapy for ocular melanoma. Int J Radiat Oncol Biol Phys 2022;

Date Published:

2022 Jul 22

Abstract:

PURPOSE: To characterize dose distributions with iodine-125 plaque brachytherapy as compared to proton radiation therapy for ocular melanoma, for relevant clinical scenarios, based upon tumor base diameter (d), apical height (h), and location. METHOD: Plaque and proton treatment plans were created for four groups of cases: 1) REF: 39 instances of reference midsize circular-base tumor (d=12 mm, h=5 mm), in locations varying by retinal clock hours, and distance to fovea, optic disc, corneal limbus; 2) SUP: 25 superiorly located; 3) TEMP: 25 temporal; and 4) NAS: 25 nasally located tumors that were a fixed distance from the fovea, but varying in d (6-18 mm), and h (3-11 mm). For both modalities, 111 unique scenarios were characterized in terms of the distance to points of interest, doses delivered to fovea, optic disc, optic nerve at 3 mm posterior to the disc (ON@3mm), lens, and retina. Comparative statistical evaluation was performed with the Mann-Whitney U-test. RESULTS: Superior dose distributions favored plaque for sparing of (i) fovea in large (d+h≥21 mm) NAS tumors; (ii) ON@3mm in REF cases located ≤4 dd (disc diameters) from disc, and in NAS overall. Protons achieved superior dose sparing of (i) fovea, optic disc in REF, SUP, TEMP; (ii) ON@3mm in REF >4 dd from disc, and in SUP, TEMP; (iii) the lens center overall, and lens periphery in REF ≤6 mm from the corneal limbus, and in TEMP, NAS with h≥5 mm. Although protons could completely spare sections of the retina, plaque dose was more target-conformal in the high-dose range (50% and 90% of prescription dose). CONCLUSION: Although comparison between plaque and proton therapy is not straightforward, due to the disparity in dose rate, prescriptions, applicators and delivery techniques, it is possible to identify distinctions between dose distributions, which could help inform decisions by providers and patients.

See also: Oncology, July 2022, All, 2022
Last updated on 07/31/2022