464 / 1082
S449
ESTRO 36 2017
_______________________________________________________________________________________________
versa. The figure outlines the normalized (with respect to
the Treatment plans) tallied quantities on patient-by-
patient basis. In 8 out of the 40 maximum doses the
Treatment plans demonstrated lower absolute doses. For
none of the 30 tallied average (or mean) doses the
Treatment plans were better than the Auto plans. The
average differences over the patient cohort range from -
7% to +36%.
Conclusion
Unattended inverse optimization holds great potential for
further personalization and tailoring of radiotherapy to
particular patient anatomies. It utilizes minimum user
time and it can be used at the very minimum as a good
starting point for personalized precision radiotherapy.
PO-0840 Hypofractionated intensity modulated
radiotherapy in patients with immediate breast
reconstruction
D.P. Rojas
1
, R. Ricotti
2
, M.C. Leonardi
2
, A. Viola
1
, S.
Dicuonzo
1
, D. Ciardo
2
, R. Cambria
3
, R. Luraschi
3
, F.
Cattani
3
, C. Fodor
2
, A. Morra
2
, V. Dell'Acqua
2
, V.
Galimberti
4
, R. Orecchia
5
, B.A. Jereczek-Fossa
1
1
European Institute of Oncology - University of Milan,
Department of Radiation Oncology - Department of
Oncology and Hemato-oncology, MIlan, Italy
2
European Institute of Oncology, Department of
Radiation Oncology, MIlan, Italy
3
European Institute of Oncology, Department of Medical
Physics, MIlan, Italy
4
European Institute of Oncology, Department of Surgery,
MIlan, Italy
5
European Institute of Oncology - University of Milan,
Department of Medical Imaging and Radiation Sciences -
Department of Oncology and Hemato-oncology, MIlan,
Italy
Purpose or Objective
The aim of the study (partially supported by a research
grant from Accuray Inc. entitled “Data collection and
analysis of Tomotherapy and CyberKnife breast clinical
studies, breast physics studies and prostate study”) is to
assess the dosimetric benefit of intensity-modulated
radiotherapy (IMRT) in postmastectomy patients with
implant–based immediate breast reconstruction (IBR),
candidates to locoregional radiotherapy with
hypofractionation.
Material and Methods
Data of the first 121 consecutive post-mastectomy
locoregional patients treated with Helical Tomotherapy
between May 2012 and May 2015 with a hypofractionated
scheme (2.67Gy/fr, 15 fractions) have been prospectively
collected. At the time of surgery, all patients underwent
IBR using either temporary tissue expander or permanent
prosthesis.
The impact of immediate breast reconstruction on the
planning was analyzed. Treatment plans were scored in
terms of coverage of the PTVs (chest wall and
supraclavicular region) and sparing of organs at risk
(heart, lungs and contralateral breast). The coverage of
chest wall and supraclavicular region was evaluated
according to the amount of volume receiving the 90% of
the prescribed dose (V
90%
) while the sparing of each OAR
was evaluated according to the number of satisfied
constrains (Tab.1). A plan with optimal coverage of both
PTVs had 2 PTV points, while a plan with optimal sparing
of all OARs had 4 OARs points. An overall score was
assigned to each plan.
Results
71.1% (86/121) of the 121 post-mastectomy radiotherapy
plans had high total scores (total score=6 points) as a
result of an optimal coverage of both chest wall and
supraclavicular region and optimal sparing of all OARs. The
remaining 28.9% (35/121) of plans had a compromised
distribution of dose (total score<6 points). In particular,
13.2% (16/121) of plans fully satisfied all the OAR
constraint but at a cost of moderate coverage of chest wall
(7/121 plans) or supraclavicular region (9/121 plans)
target volumes. On the other hand, 13.2% (16/121) of
plans fully satisfied coverage of both PTVs compromising
the sparing of OARs (heart, ipsilateral lung, or
contralateral breast). The residual 2.5% of plans (3/121)
had both coverage of PTVs and sparing of OARs
compromised.
Conclusion
In patients having implant-based IBR,
IMRT allows optimal
treatment plans in more than 2/3 of cases. Superior
dosimetric results are even more important when