Stabilised hyaluronic acid gel marker versus surgical clips for tumour bed delineation in breast cancer radiotherapy using MRI-simulation.

Abstract

Compare breast cancer tumour bed (TB) delineation using stabilised hyaluronic acid (sHA) gel and MRI-simulation versus surgical clips and CT-simulation within same patient cohort. Prospective single arm study of patients undergoing breast conserving surgery. Patients had both clips (≥5) and sHA gel markers inserted to define the TB and underwent MRI and CT simulation scans. Six observers delineated the TB aided by gel on MRI, and clips on CT. The primary measure was the inter-observer variability (inter-OV) of the delineated TB using the overlap difference of using clips and CT versus sHA gel and MRI, measured according to the general definition of the conformity index (CI_gen). Of 35 patients recruited, 30 underwent inter-OV analysis of contours and 5 required further breast surgery for positive margins. There was no significant difference in mean CI_gen between TB delineated using gel and MRI versus clips and CT (0.463 vs 0.434, p = 0.235). Observers reported higher usefulness of gel in patients who underwent oncoplastic surgery (median utility score 8.2 vs 6.6, p = 0.024), and higher visibility of gel in patients who had their scans within 6 weeks than beyond post-op (median visibility score 8.1 vs 6.1, p = 0.013). When the cavity visualisation score was higher (4-5), the median utility score of gel was lower (5.54 vs 8.0, p < 0.001), and the mean CI_gen of clips and CT delineated TB was higher (0.64 vs 0.37, p < 0.001). sHA gel has similar inter-OV of TB delineation compared to ≥5 clips, hence is a reliable alternative to clips when MRI-simulation is used.