Regression of tumour cross‐sectional area after brachytherapy for uveal melanoma: relationship between tumour height, status of Bruch’s membrane, isotope and prescription dose

Abstract

Abstract Purpose To describe regression of uveal melanoma by its cross‐sectional area rather than height in relation to characteristics of the tumour and parameters of radiotherapy. Methods For this retrospective observational study, 287 consecutive patients with choroidal and ciliary body melanoma were enrolled. They were treated with iodine or ruthenium brachytherapy from January 2000 to March 2008 and imaged with Innovative Imaging I3 ultrasound using a standard procedure. Images taken at diagnosis and at 6 months, 1, 2 and 3 years were analysed. Tumour height and area were measured with Olympus DP‐Soft from original digitised images as traced by hand. Results The reduction in the cross‐sectional area of the tumour was significantly greater if Bruch’s membrane was broken as compared to being unbroken (P=0.002 at 1 year), if the tumour involved the ciliary body (P=0.009) and, paradoxically, if the prescription dose to tumour apex was smaller (P=0.002). Use of iodine rather than ruthenium isotope (P=0.29) and tumour height were not significantly associated with regression. In a multivariate model, also the type of isotope became significant. Conclusion Reduction in tumour cross‐sectional area depends on several tumour and radiotherapy parameters, which are partially interrelated.