651 / 1082
S635
ESTRO 36 2017
_______________________________________________________________________________________________
brachial plexus D
max
was 46.7±3.0Gy with median value
46.0Gy while the thyroid gland D
mean
was 20.6±5.3Gy with
median value 20.0Gy.
Conclusion
A significant dose may be received to non-routinely
delineated organs at risk (brachial plexus, coronary artery
& thyroid gland) in post-operative loco-regional
radiotherapy of patients with left breast cancer after BCS.
A significantly higher dose was received to left ADCA in
cases with high MHD & heart V
30
while borderline
significance on ADCA in obese patients where obesity is a
known risk factor for developing coronary artery diseases.
EP-1182 Locoregional treatment of breast cancer with
IMRT: a single center experience
I. Ratosa
1
, A. Jenko
2
, R. Hudej
2
, F. Kos
2
, A. Gojkovic
Horvat
1
, D. Golo
1
, T. Marinko
1
, M.S. Paulin Kosir
1
, J.
Gugic
1
1
Institute of Oncology Ljubljana, Department of
Radiation Oncology, Ljubljana, Slovenia
2
Institute of Oncology Ljubljana, Department of
Radiation Oncology- Section of Medical Physics,
Ljubljana, Slovenia
Purpose or Objective
To evaluate implementation of breast/chest wall and
locoregional lymph nodes irradiation with inverse-planned
IMRT in patients with challenging anatomy.
Material and Methods
Since 2014, 13 patients with challenging anatomy (8 left-,
5 right-sided) were treated with locoregional IMRT on
institutional protocol because standard mono-isocentric
3D-CRT was insufficient in sparing organs at risk (OARs).
Dose prescription to planning target volume (PTV) was 50
Gy in 25 daily fractions; 3 patients were also prescribed
boost dose 10−16 Gy. Treatment planning was done on
Elekta Monaco TPS with Monte Carlo calculation
algorithm. In the IMRT plan 9 beams with the energy of 6
MV were positioned so that the first two beams were
placed tangentially on the PTV (as in a 3D-CRT plan) and
the rest were redistributed equidistantly between the
tangential pair. The cranial part of beams that would pass
through the shoulder into the PTV was blocked with jaws.
Two segmetation methods were used, Step-and-Shoot for
the first 7 patients and Dynamic MLC (dMLC) for the rest.
The primary endpoint in treatment planning was CTV
coverage. Radiation was delivered on Elekta Synergy™
Platform linac for Step-and-Shoot mode and Elekta Versa
HD™ for dMLC mode.
Results
: 12 patients had mastectomy and 1 patient had
lumpectomy. 7 patients had immediate reconstruction: 2
tissue expanders, 5 autologous deep inferior epigastric
perforator flaps. All patients received systemic
chemotherapy. Toxicity was evaluated once weekly. 84 %
(11/13) of patients had G1 skin toxicity, while 15 % had
G2-G3 (2/13) toxicity. In one patient with G3 toxicity skin
dose was intentionally increased with a bolus. 1 patient
had G1 esophagitis and there was no acute lung toxicity.
CTV coverage was within limitations for all patients
(V
93%
PD > 99%). For evaluation PTV (target volume reduced
by 5mm buildup region) the selected target dosimetric
metrics were the following: for left-sided breast
treatment V
95%
PD = 96.8% (standard deviation – SD 3.7%),
V
107%
PD = 3.7% (SD 5.4%) and for right-sided breast
treatment V
95%
= 96.3% (SD 4.7%), V
107%
PD = 1.0% (SD
0.7%). Dosimetric metrics for OARs for the whole group
were: heart D
mean
= 5.6 Gy (SD 3.2 Gy), V
20 Gy
= 4.9% (SD
6.4%), for both lungs D
mean
= 9.6 Gy (SD 1.7 Gy), V
20 Gy
=
15.9% (SD 3.4%), for contralateral lung V
5 Gy
= 8.7% (SD
16.8%) and for contralateral breast D
mean
= 1.7 Gy (SD 1.0
Gy). Dose to the OARs and restrictions are presented
separately for left and right side in table 1.
Conclusion
Conclusion
: IMRT of breast/chest wall and regional lymph
nodes in patients with challenging anatomy is feasible with
acceptable short term toxicity. We had some difficulties
in balancing constraints for OARs and target coverage
especially in left-sided breast treatment. Better results
may be achieved with the introduction of deep inspiratory
breath hold (DIBH) combined with IMRT or even VMAT
technique.
EP-1183 Initial Clinical Experience with a Noninvasive
Breast Stereotactic Radiotherapy Device: the
GammaPod
S. Feigenberg
1
, E. Nichols
1
, Y. Mutaf
1
, W. Regine
1
, S.
Becker
1
, Y. Niu
2
, C. Yu
1
1
University of Maryland School of Medicine, Radiation
Oncology, Baltimore, USA
2
Xcision Medical Systems, Research, Columbia- MD, USA
Purpose or Objective
GammaPod
TM
is a new stereotactic radiotherapy device
dedicated to the treatment of breast cancer. It creates a
radiation focal spot with sharp dose fall-off at the
isocenter by using 36 non-overlapping rotating cobalt-60
beams, and creates a uniform dose coverage by
dynamically moving the focal spot within the breast in the
prone position. A US FDA approved clinical study is being
conducted at the University of Maryland. Herein reported
is the initial experience with this novel device.
Material and Methods
The purpose of this clinical study is to evaluate the
feasibility and safety of using the GammaPod
TM
system to
deliver a focal dose of radiation to a target in the
breast. Of the 17 planned enrollments, 6 patients have
been completed and we expect to complete this trial by
the end of 2016. A single ‘boost’ dose of 8 Gy is delivered
post-operatively to the tumor bed plus a 10mm margin
using the GammaPod
TM
, followed by whole breast
irradiation with either hypofractionation of 15 fractions or
a conventional fractionation scheme of 25
fractions. Eligibility criteria include minimum age of 60,
with Stages I or II breast cancer, lumpectomy volume less
than 30% of the whole breast volume, and the lumpectomy
within the immobilized breast. Prior to treatment, the
affected breast is immobilized with a patented vacuum-