ESTRO 36 Abstract Book

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S615 ESTRO 36 2017
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myeloablative chemotherapy prior to stem cell transplant.
Here we report our initial clinical experience regarding
patient setup error and its dosimetric consequences.
Material and Methods
7 patients with advanced hematological malignancies
were treated according to our institutional phase I clinical
trial designed to evaluate the feasibility of IMTMI in
addition to preconditioning chemotherapy regimen.
Patients were immobilized using a customized whole body
mold. The bones are contoured and a 3 mm margin is
added to obtain PTV. Three separate treatment plans, for
the head and neck, chest, and pelvic were generated.
Plans were optimized for 95% PTV coverage with the 95%
of prescription dose. Positioning and alignment of all three
isocenters were confirmed prior to each treatment with
megavoltage orthogonal port films. Residual setup errors
of each patient and each fraction were retrospectively
analyzed by co-registering port films and digitally
reconstructed radiographs. Dosimetric consequences of
setup errors were evaluated by shifting the isocenters
based on the determined setup errors. We applied
previously determined actual isocenter shifts for each
session and recalculated dose distributions to determine
delivered dose distributions. Simulated dose distributions
were then compared with the planned dose distributions.
Results
Setup errors were less than 5 mm, more specifically, they
were, on average, 3.1±0.7 mm, 2.3±0.8 mm, 3.2±0.8 mm
in vertical, longitudinal, and lateral directions,
respectively. Maximum vectoral displacement was 4.6
mm. When the determined isocenter shifts were applied
and the new dose distributions were calculated, the bone
marrow volume that received the 95% of the prescription
dose (V95) was reduced from 99.4% (±0.7%) to 96.8%
(±1.3%), on average. The mean lung dose and the mean
PTV dose changed less than 5%. The change in the
maximum dose ranged between 6% and 19%.
Conclusion
Linac-based IMTMI is clinically feasible affording
significant OAR sparing in a combined chemo-RT
treatment. Based on our clinical experience with the first
7 patients in this study, we found a 3 mm bone to PTV
expansion was adequate to accurately target bone marrow
in IM-TMI treatments.
Electronic Poster: Clinical track: Breast
EP-1139 eliot- boost and conservative surgery followed
by hypofractionated EBRT in breast cancer patients
S. Takanen1, G. Gritti 1, M. Källi1, L. Feltre 1, F. Filippone1,
E. Iannacone 1, L. Maffioletti1, R. Muni1, P. Fabio1, E.M.P.
Mauri2, M. Giovanelli2, L. Burgoa2, A. Paludetti2, C.
Valerii 2, F. Palamara2, M. Ferro2, P. Fenaroli2, S.
Andreoli3 , M. Fortunato3, L.F. Cazzaniga1
1 Azienda Socio-Sanitaria Territoriale Papa Giovanni XXIII,
Radiation Oncology, Bergamo, Italy
2 Azienda Socio-Sanitaria Territoriale Papa Giovanni XXIII,
Breast Cancer Surgery, Bergamo, Italy
3 Azienda Socio-Sanitaria Territoriale Papa Giovanni XXIII,
Medical Physics, Bergamo, Italy
Purpose or Objective
We report preliminary results from a clinical trial aimed
to evaluate the incidence of in-breast tumour recurrence
(IBR) and the acute and late toxicity in patients affected
by early breast cancer (BC), undergoing conservative
surgery and electron intraoperative radiation (ELIOT)
boost, followed by hypofractionated external beam
radiotherapy (EBRT).
Material and Methods
From February 2012 to January 2016, 83 early BC patients
underwent conservative surgery and ELIOT boost, followed
by EBRT at Papa Giovanni XXIII Hospital in Bergamo (Italy).
Patients inclusion criteria are: infiltrating carcinoma
histology (T1-2, N0-1, M0), unifocality or multifocality
(maximum distance between two lesions ≤ 2 cm), PS
(ECOG) ≤ 2, age > 18, premenopausal status.
ELIOT boost was delivered for all patients at the level of
tumour bed by a dedicated linear accelerator NOVAC 7
HITESYS (NRT, Italy), using 9 MeV electron beam, a single
dose of 12 Gy at 90%.
EBRT was given at the whole breast in 13 daily fractions of
2.85 Gy.
Fifteen patients underwent adjuvant chemotherapy and
74 patients underwent hormone therapy.
IBR is any local relapse within the treated breast. Acute
and late toxicity were assessed using RTOG toxicity scale.
Results
Forty-seven patients (56.6%) started EBRT boost in 28 days
after ELIOT boost procedure.
Current median follow up was 23 months and is too short
to evidence any IBR.
After ELIOT, 2 patients underwent mastectomy, after the
identification of another breast metachronous nodule and
BRCA1 mutation respectively. Four patients underwent
conventional scheduled EBRT: 3 for the presence of
unfavourable prognostic disease factors as discovered on
the surgical specimen and 1 for severe post-surgical side
effects.
Most patients had slight local post-surgical oedema: 1
patient had necrosis of the scar area. After EBRT, slight
skin erythema (G1) was evidenced in all patients.
Considering late toxicity, slight scar fibrosis (G1) was
assessed in most patients: 1 patient showed scar
retraction and 1 dehiscence of surgical scar.
Conclusion
The advantages of the ELIOT-boost followed by
hypofractionated EBRT in early BC are the reduction of
treatment duration and skin toxicity with better cosmetic
results, the delineation of tumour bed under direct visual
and palpable evaluation, no adjuvant chemotherapy delay
and the immediate inhibition of cells repopulation. With
these preliminary results, it seems to be manageable with
acceptable acute toxicity. A longer follow up is needed in
order to show IBR and late effects rate.
EP-1140 Dosimetric comparison between Helical
Tomotherapy and IMRT for Bilateral Breast Cancer
M.H. Wang1
1Shuang Ho Hospital, Department of Radiation Oncology,
Taipei, Taiwan
Purpose or Objective
This study aimed to compare treatment between
Tomotherapy and IMRT for bilateral breast cancer.
Material and Methods
We selected 10 patients of breast cancer who were
performed partial mastectomy for study. All patient were
early stage breast cancer pT1~T2. A total dose of 5040cGy
was delivered for definitive breast irradiation of IMRT and
Tomotherapy for each patient in treatment planning
system. In this study, we analyzed comparable treatment
of IMRT vs Tomotherapy for bilateral breast. Bilateral
whole breast dose coverage, Conformity index,
Homogeneity index and dose volume constraints of normal
tissue (Right and Left lung, Heart) were analyzed.
Results
Tomotherapy was better than IMRT for significant
improvements in reducing the volume of normal tissue. In
volume of heart in V20 (Tomo:1.543% versus IMRT: 2.955%;
p=0.023) and in lung volume achieving lower mean lung
dose (MLD) (Rt lung mean dose: Tomo: 6.388 Gy versus
IMRT: 8.828Gy; p = 0.017; Lt lung mean dose Tomo: 6.24
Gy versus IMRT: 7.71Gy; p = 0.013). The conformity indices
(V95%/VPTV) of right and left breast were (1.08 +/- 0.01) &
(1.07 +/- 0.02) in Tomo and (1.07 +/-0.02) & (1.08 +/-
0.01) in IMRT. For homogeneity indices, Tomo were (1.36