The use of hyaluronic acid hydrogel as a tumour bed marker in breast-conserving therapy.

Abstract

To evaluate usefulness of hyaluronic acid (HA) hydrogel as a tumour bed marker in breast conserving therapy (BCT). To analyze inter- (Inter-OV) and intraobserver (Intra-OV) variability of contouring boost target volume (CTV_boost) in external beam radiotherapy (EBRT). Thirty-two patients in the HA group and 30 patients in the control group with an early stage breast cancer were included in the study. During the surgery 1-3 ml of HA hydrogel was injected into breast to mark the tumour bed for every patient in the HA group. Moreover, surgical clips were placed underneath the lumpectomy cavity. Patients in the control group were marked only by metal markers. Three radiation oncologists delineated CTV_boost twice for every patient. Three parameters were calculated to quantify contouring variability: coefficient of variation for volumes (COV_V), center of mass displacement (CoMd) and conformity index (CI). There were no significant differences between mean values of COV_V for HA and control group, neither for Intra-OV (0.14 vs 0.13) nor Inter-OV (0.19 vs 0.18) calculations. The mean CoMd were 6.1 mm and 9.1 mm for Inter-OV calculations and 3.9 mm and 6.4 mm for Intra-OV in the HA and the control group respectively. The mean CI for Intra-OV improved from 0.61 to 0.65 and from 0.47 to 0.56 for Inter-OV in the control and HA group respectively. HA hydrogel used as a tumour bed marker improves tumour bed visibility and reduces inter- and intraobserver variability of EBRT boost target volume delineations.