Ultrasonography and transillumination for uveal melanoma localisation in proton beam treatment planning

Abstract

Background/Objective: The success of proton beam treatment (PBT) in uveal melanoma depends in part on the accuracy of tumour localisation. This study determined if using ultrasonography (US) to measure the distance between tumour margin and tantalum ring (DTR) in PBT planning improves local treatment success when compared with using intraoperative transillumination (TI) alone. Methods: Retrospective analysis of patients with uveal melanoma treated at one centre between January 2006 and June 2017 with ≥12-month follow-up (or until treatment failure). Local tumour control was compared among study groups based on methods for measuring DTR: Group 1 (TI alone), Group 2A (postoperative US alone) and Group 2B (combination). Results: Fifty-four eyes (54 patients) with uveal melanomas were included: Group 1 (22 eyes, 41%), Group 2A (11 eyes, 20%) and Group 2B (21 eyes, 39%). Mean age at diagnosis was 64 years [median 66 years, range 23–86 years]. Fifty tumours (93%) involved the choroid, while four involved the ciliary body (7%). In Group 2B, PBT treatment was based on the DTR obtained using US; DTR differed between TI and US by ≥1 mm for 25 rings in 16 eyes and ≥2 mm for 12 rings in 7 eyes. Five-year Kaplan–Meier estimate revealed a difference in local treatment success between Groups 1 and 2, (0.82 vs. 1.0, p = 0.02) with no difference in overall survival estimate, (0.85 vs. 0.83, p = 0.8). Conclusions: US can be used to measure DTR in PBT planning for uveal melanoma. This may improve accuracy of tumour localisation and improve local treatment success.