The use of hyaluronic acid hydrogel as a tumour bed marker in breast cancer brachytherapy.
Judyta Wiercińska,
Poland
OC-0629
Abstract
The use of hyaluronic acid hydrogel as a tumour bed marker in breast cancer brachytherapy.
Authors: Judyta Wiercińska1, Janusz Winiecki1, Anna Wronczewska2, Andrzej Lebioda3, Piotr Rhone4, Krzysztof Pławski4, Roman Makarewicz3
1Oncology Center in Bydgoszcz, Medical Physics Department, Bydgoszcz, Poland; 2Oncology Center in Bydgoszcz, Brachyterapy Department, Bydgoszcz, Poland; 3Oncology Center in Bydgoszcz, Brachytherapy Department, Bydgoszcz, Poland; 4Oncology Center in Bydgoszcz, Department of Breast Cancer and Reconstructive Surgery, Bydgoszcz, Poland
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Purpose or Objective
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 brachytherapy (BT) and evaluate
the impact of target volume delineation variability on dosimetric
parameters in breast cancer BT.
Material and Methods
32
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 to 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 (COVV ), center of
mass displacement (CoMd) and conformity index (CI). The dosimetric
impact of contouring variability was determined by using an actual,
executed treatment plan without any changes in dwell positions and
dwell times for other CTV boost delineations and calculating DVH
parameters for these structures. D90 and V100 parameters were chosen
as a metric.
Results
The
study showed decreased differences of the brachytherapy CTV boost
planning. The mean COVV decreased in HA group comparing
to control group from 0.26 to 0.17 for Inter-OV analysis and from
0.14 to 0.12 for Intra-OV analysis. The mean CoMd were 6.2 mm and 8.6
mm for Inter-OV calculations and 4.1 mm and 6.6 mm for Intra-OV in
the HA and the control group respectively. The mean CI for Inter-OV
improved from 0.51 to 0.58 and from 0.62 to 0.69 for Intra-OV in the
control and HA group respectively.
Applying
dwell positions and times from original treatment plan to other CTVs
boost resulted in reduction of D90 and V100 values below the plan
acceptance requirements in both analyzed groups. However, the
decrease in HA group was significantly smaller than in the control
group, both for D90 (78,57% vs 67,60%) and V100 (77,37% vs 68,09%)
for HA and the control group respectively.
Conclusion
HA
hydrogel used as a tumour bed marker reduces inter- and intraobserver
variability of BT boost target volume delineations. The study has
proven, that the delineation variability results in D90 and V100
parameters falling below the recommended threshold. However marking
the tumour bed with HA hydrogel minimized the reduction of impact on
those parameters comparing to the control group.