Abstract
Purpose :
In patients undergoing plaque brachytherapy for uveal melanoma, a change in tumor size between the time of initial tumor measurements and the time of plaque placement can result in inadequate radiation dose delivered to the tumor apex. The purpose of this study was to determine whether clinical or imaging tumor characteristics may predict which melanomas may grow rapidly prior to plaque placement, to aid the surgeon in treatment planning.
Methods :
A retrospective chart review was performed of 60 patients who had ultrasonography repeated preoperatively and compared to the tumor dimensions at time of initial evaluation. “Significant” tumor growth was defined as 15% change from initial apical height measurement. Data variables collected were largest basal diameter(LBD), time from initial evaluation to plaque placement, gene expression profile (GEP), presence of retinal invasion, Bruch’s membrane rupture, and tumor location. It was noted if a change in treatment plan was made (such as delaying plaque removal, need for plaque redesign, or a change in planned treatment modality). Statistical analysis was performed with R software and ggplot2. Fisher’s exact test and odds radio analysis were used to examine the correlation between clinical tumor factors and significant tumor growth.
Results :
Of 60 patients, 5(8.3%) had documented significant tumor growth. Among all patients, the average time between initial measurements and plaque brachytherapy placement was 17.3 ± 6.8 days. Days from initial evaluation to plaque placement were correlated with interval tumor growth (p=0.020). However, tumor-related factors such as presence of Bruch’s membrane rupture or retinal invasion, tumor configuration or location, higher apical height, LBD, and GEP were not independently predictive of tumor growth.
Conclusions :
One out of every 12 patients for whom brachytherapy was planned ultimately demonstrated >15% interval growth prior to plaque placement, based on repeat measurements. Likelihood of interval growth was associated with the length of time between plaque planning and placement. Since there were no specific tumor features that could be relied on to predict which tumors would grow, the interval between the time of patient evaluation/radiation planning and the time of surgical plaque placement should be minimized in all patients, and repeat ultrasound measurements immediately prior to surgery may be considered.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.