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S243
ESTRO 36
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Purpose or Objective
The objective was to study the differences in target
coverage and dose-volume parameters for heart and lung
between Deep Inspiration Breath Hold (DIBH) 3D
Conformal Radiation Therapy (3D-CRT), DIBH Volumetric
Modulated Arc Therapy (VMAT) and free breathing
Intensity Modulated Radiation Therapy (IMRT) in patients
treated with synchronous bilateral breast cancer.
Material and Methods
This planning comparative study was conducted in nine
patients previously treated for synchronous bilateral
breast cancer. These patients were treated with either
DIBH 3D-CRT or IMRT in free breathing. All patients were
treated with whole breast irradiation and those requiring
a boost were given a simultaneously integrated boost
(SIB). Three treatment plans were constructed for each
patient individually; a DIBH 3D-CRT plan, a DIBH VMAT
plan and an IMRT plan in free breathing. DIBH IMRT is
clinically not feasible due to the extended duration of
treatment. Three patients were treated without a boost,
three were treated with unilateral SIB and the remaining
patients were treated with double sided SIB. DIBH 3D-CRT
plans were created using tangential fields for both breasts
and up to three boost fields for each breast, if a boost was
required. IMRT plans were created using 14 fields around
the patient, 24° apart, covering both breasts and
simultaneously covering the boost target in one or both
breasts. DIBH VMAT plans without boost targets were
created using eight 30° arcs, four on each side, oriented
in a tangential design. Four 60° arcs, in a tangential
design, were used in patients with boost targets, two for
each breast, with an additional semi-circle arc on either
side covering the boost targets. The parameters reviewed
were V95% (percentage of volume receiving 95% of the
prescription dose) PTV1 and PTV2 coverage, with PTV1
being the elective target and PTV2 the boost target, the
mean heart dose and heart left ventricle V5 (percentage
of volume receiving 5 Gy), mean lung dose, lung V5 and
lung V20. The parameters were compared using the paired
T-test for normally distributed data and the Wilcoxon
signed rank-test for not normally distributed data. Three
statistical analyses were performed on each parameter,
therefore the Bonferroni correction was applied.
P
≤0.016
was considered statistically significant in this study.
Results
Target coverage of PTV1 and PTV2 were comparable
between the three techniques (table 1), except the V95%
PTV1 left. All dose volume parameters of the heart and
lung were lower for the DIBH VMAT technique (table1) in
comparison with the DIBH 3D-CRT and free breathing IMRT
technique.
Conclusion
DIBH VMAT is the most optimal radiation technique in the
treatment for patients with synchronous bilateral breast
cancer. Both PTV coverage and the sparing of the organs
at risk give better results for DIBH VMAT in comparison
with DIBH 3D-CRT and IMRT in free breathing.
PV-0457 Delay between planning and stereotactic
radiotherapy for brain metastases: margins still
accurate?
C. Bonnet
1
, A. Dr Huchet
1
, E. Blais
1
, J. Dr Benech-Faure
1
,
R. Dr Trouette
1
, V. Dr Vendrely
1
1
Hopital Haut Leveque, Radiotherapy, Pessac, France
Purpose or Objective
Advances in intracranial stereotactic radiotherapy have
led to high gradient dose between tumor and normal tissue
and to dramatically reduced Planning Target Volume (PTV)
margins. Accurate definition of the gross tumor volume
(GTV) for stereotactic radiotherapy of brain metastases is
an essential key for the treatment planning. However, its
underestimation due to tumor growth during the delay
between planning and stereotactic radiotherapy may lead
to treatment failure.
Our purpose was to evaluate the tumor growth kinetics
and its impact during the delay before treatment of brain
metastasis secondary to lung cancer (LC) or melanoma
(ML).
Material and Methods
This retrospective monocentric study included all
consecutive patients (pts) treated for brain metastases
secondary to LC or ML between June 2015 and May 2016.
Margins from GTV to PTV were 2 mm. Imaging at diagnosis
of brain metastasis and preplanning imaging were
compared; GTV corresponding to the contrast
enhancement was analyzed. Linear extrapolation was used
to determinate the n minimum theoretical time leading
the diameter of the tumor to increase more than 4 mm
(T4mm).
Results
Out of 103 pts treated for brain metastasis by stereotactic
radiotherapy, 50 were treated for metastases secondary
to LC (n=26) or ML (n=24). Six pts were excluded because
of lack of imaging data. Median age was 68 years old
(range: 25-92). RPA status was 1 for 1 patient (2%), 2 for
33 pts (79%) and 3 for 8 pts (19%). Systemic treatment was
given at diagnosis for 19 pts (45 %). Radiotherapy was
delivered according to a monofraction scheme for 8 pts (3
LC and 5 ML metastasis), 3-fraction scheme (23 LC, 18 ML)
or 5-fraction scheme (2 LC, 3 ML).
A hundred and eight brain imaging (84 MRI, 24 CT-scan)
were analyzed. Comparison of imaging at diagnosis and
preplanning treatment showed bleeding inside metastasis
for one patient with primary LC; increased tumor volume
for 40 pts (ML n=25 ; LC n=15) ; stability for 11 pts (ML n=1
; LC n=10) and decreased volume for one LC patient.
Median delay between brain imaging at diagnosis and
pretreatment planning were: 28 days (range 8-107) for ML
pts and 31.5 days (range 7-70) for LC pts. Median Volumes
of GTV at diagnosis were 0.5 cm3 (range 0.05-8.6cm
3
) for
ML pts and 0.45cm
3
(range 0.05-6.1cm
3
) for LC pts; median
volumes of preplanning treatment GTV were 1.55 cm
3
(range: 0.2-9.9cm
3
) for ML pts and 0.85 (range 0.2-
10.4cm
3
) for LC patients. Linear extrapolation revealed a
median increase of tumor volume of 0.16 cm3/wk (range
0-0.8 cm3/wk) for ML and 0.06 cm3/wk (range 0-0.5
cm3/wk) for LC. Shorter T4mm was 15 days for ML patients
and 17 days for LC pts.
Conclusion
Maximal delay for treatment appeared to be 15 days for
ML patients and 17 days for LC patients to ensure that
tumor radius has grown less than to 2 mm. Above this
delay, clinicians should reconsider planning of treatment.
PV-0458 FMECA of Cyberknife process: two years’
experience for improvement
S. Cucchiaro
1
, D. Dechambre
1
, T. Massoz
1
, N. Gourmet
1
,
D. Boga
1
, N. Jansen
1
, P. Coucke
1
, M. Delgaudine
2
1
C.H.U. - Sart Tilman, Radiotherapy Departement, Liège,
Belgium
2
C.H.U. - Sart Tilman, STA Quality Departement, Liège,
Belgium
Purpose or Objective
Failure Modes Effects and Criticality Analysis (FMECA) is a
risk analysis allowing the identification of causes and