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ESTRO 36 2017
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Conclusion
The reduction of the longitudinal margin from 4 cm to 3
cm can significantly reduce the dose to lungs, while the
reduction to 2 cm can also reduce doses to the heart.
Despite clinical benefit and oncologic outcome remain
unclear, reduction of the longitudinal margins might
provide the opportunity to reduce side effects of CRT for
SCC in upcoming studies.
EP-1824 Elective breast RT including level I & II
lymph nodes: A planning study with the humeral head
as PRV
J. Van der Leer
1
, K. Surmann
1
, M. Van der Sangen
1
, M.
Van Lieshout
1
, C.W. Hurkmans
1
1
Catharina Ziekenhuis, Radiotherapy, Eindhoven, The
Netherlands
Purpose or Objective
The aim of this planning study was to determine a new
technique for elective breast radiotherapy and level I and
II lymph nodes following the new ESTRO delineation
consensus guidelines. According to these guidelines the
humeral head should be spared by introducing a planning
risk volume (PRV) of the humeral head and connective
tissue 10 mm around it.
Material and Methods
We included ten left sided breast cancer patients in our
planning study in Pinnacle
3
v9.8. Each patient was planned
with 16 x 2.66 Gy on the breast PTV (PTVp) and the
elective level I and II lymph nodes (PTVn).
We compared three treatment planning techniques: high
tangential field (HTF), 6-field IMRT and VMAT. The HTF
technique consisted of two open beams with extra
segments and the cranial and posterior border was
extended to include PTVn. Some of the leaves were closed
to spare the humeral head + 10 mm around it (hh+10). For
the IMRT technique we added four additional fields to the
high tangential fields (gantry angle of 330, 30, 80 and 170
degrees) to ensure coverage of the cranial part of the
breast and lymph nodes. The caudal border of these
additional fields was set 1 cm below the attachment of the
clavicle at the sternum. The third technique was a dual
arc VMAT from 305 to 180 degrees.
The plans were made by inverse planning, achieving a
PTVp coverage of V95% ≥ 97% and a PTVn V90% ≥ 95%.
Additionally, the dose to the lungs, heart and right breast
(OARs) has been minimized. hh+10 was included with an
objective of V40Gy < 1 cm
3
for all three techniques.
Results
HTF resulted in an average PTVp V95% of 97.2% and an
average PTVn V90% of 90.4% (see Table 1 and Figure 1).
With the additional fields of the IMRT technique the
coverage of PTVn increased significantly to on average 98%
(p=0.01) while PTVp did not vary significantly (p=0.92).
The dose to the OAR was comparable between the HTF
and IMRT techniques. When using VMAT the coverage of
the PTVn was on average 99.5% (p<0.01 compared to the
HTF and p=0.19 compared to IMRT). The dose to the OARs
however increased as well. The mean dose to the
contralateral breast increased significantly from 0.6 Gy
with HTF and IMRT to 2.3 Gy with VMAT (p<0.01 for both).
Conclusion
Both the 6-field IMRT and the VMAT technique can be used
to spare the humeral head and surrounding tissues as
aimed for in the ESTRO guidelines while still achieving
proper target coverage. The IMRT technique discussed in
our study resulted in a lower dose in the OARs and
consequently this technique has been implemented in our
institute.
EP-1825 Evaluation for the usability of the Varian
Standard Couch modeling using Treatment Planning
System
Y.M. Yang
1
, Y.M. Song
1
, J.M. Kim
1
, J.M. Choi
1
, B.K. Choi
1
1
Samsung Medical Center, Radiation Oncology, seoul,
Korea Republic of
Purpose or Objective
When a radiation treatment, there is an attenuation by
Carbon Fiber
Couch.
In this study, we tried to evaluate the usability of the