ESTRO 36 Abstract Book

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S641 ESTRO 36
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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
(V93%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 V95%PD = 96.8% (standard deviation – SD 3.7%),
V107% PD = 3.7% (SD 5.4%) and for right-sided breast
treatment V95% = 96.3% (SD 4.7%), V107% PD = 1.0% (SD
0.7%). Dosimetric metrics for OARs for the whole group
were: heart Dmean = 5.6 Gy (SD 3.2 Gy), V20 Gy = 4.9% (SD
6.4%), for both lungs Dmean = 9.6 Gy (SD 1.7 Gy), V20 Gy =
15.9% (SD 3.4%), for contralateral lung V5 Gy = 8.7% (SD
16.8%) and for contralateral breast Dmean = 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. Feigenberg1, E. Nichols1, Y. Mutaf1, W. Regine1, S.
Becker 1, Y. Niu2, C. Yu1
1 University of Maryland School of Medicine, Radiation
Oncology, Baltimore, USA
2 Xcision Medical Systems, Research, Columbia- MD, USA
Purpose or Objective
GammaPodTM 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 GammaPodTM 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 GammaPodTM, 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-
assisted breast cup and imaged on a CT simulator with 1
mm slice thickness. Once the cup is placed, the negative
pressure is maintained until the treatment is
delivered. An inversely optimized treatment plan is
generated while the patient is transported and positioned
in the treatment room. Typical time between the imaging
session and completion of treatment is about 60 minutes.
Results
5 of the first 6 enrolled patients completed the
treatment. One patient’s lumpectomy cavity extended
outside the immobilized portion of the breast and
therefore did not meet the inclusion criteria for the study.
With the sources near its half-life, the treatment time
ranged from 17 minutes to 26 minutes. Dosimetrically, for
the 5 patients who completed their treatment, more than
95% of the prescription dose covered the clinical target
volume, and the maximum dose (D2% ) varied from 13% to
20% of the prescription dose (see figure of sample dose
distribution). With a median follow-up of 3 months, none
of the patients developed treatment related toxicity.
Conclusion
Initial results indicate that the GammaPod system can
deliver a focal dose of radiation to the breast safely. The
vacuum-assisted breast cups were able to maintain the
immobilization between imaging and treatment. With
dynamic dose painting, the dose uniformity rivals that of
external beam partial breast irradiation, but with more
rapid dose fall-off outside the target, leading to
substantially reduced radiation dose to the normal
breast. The ability of delivering a focal dose of radiation
opens the opportunity for single pre-operative irradiation
as an alternative to intra-operative irradiation and pre-
operative radioablation.
EP-1184 HDR boost decreases the risk of breast failure
in invasive breast ca. with close or involved margins
J.L. Guinot 1, M.I. Tortajada1, M.A. Santos1, F. Romero1,
A. Moreno2, V. Campo3, L. Oliver3, P. Santamaria1, J.
Fernandez4, L. Arribas1
1Fundación Instituto Valenciano de Oncologia,
Department of Radiation Oncology, Valencia, Spain
2Fundación Instituto Valenciano de Oncologia,
Department of Radiation Oncology, Alcoy Alicante, Spain
3Fundación Instituto Valenciano de Oncologia,
Department of Radiation Physics, Valencia, Spain
4Fundación Instituto Valenciano de Oncologia,
Department of Radiation Oncology, Cuenca, Spain