ESTRO 36 Abstract Book

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S968 ESTRO 36 2017
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evaluations were performed. The maximum doses
received by the rectum wall, bladder wall, bowels and PTV
were analyzed and traced over the five fractions to
determine the total dose distribution over the entire
prescribed treatment.
Results
No contour of any of the OAR was exactly similar when CT
images were fused to each other. Depending on the depth
of the insertion the PTV varied minimally. Each plan was
performed independently and cumulated 2 at a time until
all 5 fractions were added to the initial fraction. There is
a difference between the doses received by the OARs
between treatments and between the points of maximum
does. The PTV volumes vary from fraction to fraction. The
maximum dose varied between 12% and 27% in rectum wall
and bladder wall. The minimum dose varied between 2%
and 7% in rectum wall and bladder wall. The average dose
varied between 9% and 21% in rectum wall and bladder
wall. The cumulative treatment does do not indicate a
total maximum dose exceeding the tolerances for the
rectum and bladder.
Conclusion
The variation in volumes of OARs and isodoses near the
OARs, indicate that the estimated doses to OARs on the
planning system may not be the same dose delivered to
the patient in all the fractions. There are no major
differences between the prescribed dose and the
delivered dose over the total number of fractions.
Variation in the length of the cylinder part implanted into
the vagina and PTV's coverage indicates an inconsistency
in the entire vaginal cuff in all five fractions. In some
cases, the critical organs will benefit if the consecutive
plans will be made after the CT scans are registered with
the initial. All the cases studied indicate the need for more
detailed study in order to establish a protocol of planning.
EP-1788 HDR vs LDR Vaginal brachytherapy: a
comparison in terms of outcomes and toxicity
R. Autorino1, D. Smaniotto1, M. Campitelli1, L.
Tagliaferri1, A. Nardangeli1, G. Mattiucci1, A. Martino1, N.
Di Napoli 1, G. Ferrandina 2, M. Gambacorta1, V. Valentini1
1 Polyclinic University A. Gemelli- Catholic University,
Institute of Radiotherapy, Rome, Italy
2 Polyclinic University A. Gemelli- Catholic University,
Institute of Oncological Gynecology, Rome, Italy
Purpose or Objective
To compare the outcomes in terms of survival and toxicity
for endometrial carcinoma patients treated with either
HDR or LDR vaginal brachytherapy (VBT) after external
beam radiotherapy
Material and Methods
From January 2000 to December 2014, patients with
endometrial cancer after radical hysterectomy +/- pelvic
and/or lombo-aortic lymphadenectomy were treated with
adjuvant radiotherapy (45 Gy, 1.8 Gy/day on the whole
pelvis) and subsequential VBT boost (HDR dose was 7 Gy in
one fraction prescribed to 0.5 cm from the surface of the
applicator; LDR dose was 25 Gy to the vaginal mucosa).
The outcomes of patients were evaluated in terms of local
control (LC), overall survival (OS) and toxicity (according
to CTCAE v 4.0).
Results
We retrospectively analyzed 200 patients treated with
external beam radiation therapy followed by a HDR VBT
boost in 78 patients and LDR VBT boost in 122 patients.
Patients characteristics are summarized in Table 1.With a
median follow-up of 25 months (range 1-163), 5-ys overall
suvival (OS) was 98% vs 97% in LDR and HDR group
respectively (p=0.37) and 5-ys local control (LC) was 93%,
similar in the two groups (p=0.81).At multivariate
analyses, any factors (age, stage, grading) seems to have
impact on OS (p=0.37) and LC (p=0.81). Patients treated
with LDR VBT after external beam radiotherapy had an
higher gastrointestinal acute toxicty; probably, this is due
to development of radiation tecnique over the years of
this study. No differences was found in terms of acute
genitourinary and hematological toxicity. Late toxicity
such as vaginal stenosis was registered during regular
follow-up visit by clinical evaluation. We didn’t find
statistically significant differences between the two
modalities (p=0.67).
Conclusion
With the limits of a restrospective review, there were no
differences in survival and late toxicity outcomes for
patients receiving LDR or HDR brachytherapy. HDR is safe
technique in comparison to LDR modality. A larger
database analysis will confirm outcomes and toxicity of
HDR VBT in postoperative endometrial cancer.
EP-1789 Comparison between MRI based 3D IGABT
planning versus standardised BT planning of cervical
cancer
M. Hedetoft1
1Skåne University Hospital, Department of Radiation
Physics, Lund, Sweden
Purpose or Objective
The aim of this study was to investigate if the introduction
of MRI based Image Guided Adapted Brachy Therapy
(IGABT) treatment planning of cervical cancer in our
hospital, has improved the target coverage and reduced
the dose to Organs at Risk (OAR) in comparison to standard
treatment planning with point A dose prescription.
Material and Methods
In February 2014 the first brachytherapy treatment of a
cervical cancer patient planned with MRI based 3D IGABT
technique, was undertaken in Lund. Until the end of
August 2016, 38 patients have been treated with this
technique resulting in 142 fractions, all of them included
in this study. The tumour stages of the patients included
were IB1 (n=5), IB2 (n=5), IIA (n=7), IIB (n=16), IIIB (n=5).
Each patient received external beam radiation therapy
and 2 or 4 brachytherapy fractions depending on the
tumour stage. For brachytherapy treatments the
interstitial titanium ring and tandem applicator (Varian
Medical Systems) were used. To be able to choose if an
interstitial treatment would improve the tumour coverage
a pre-plan was always done. 21 patients were selected for
intracavitary/interstitial implant and 17 for intracavitary
implant only.
Based on the MRI target volumes, GTV, HR-CTV, IR-CTV
and OARs (bladder, rectum, sigmoid and bowel) were
contoured according to GEC-ESTRO recommendations. The
dwell times were optimised for each fraction, 6.5 Gy/fr
and the plans were evaluated according to DVH criteria
from the EMBRACE II study.
For all fractions the optimised 3D plan was compared to a
2D plan with standardised dwell times, the same pre-plan
that was used for patient treatments before starting with
the IGABT. The standard plan was based on the same MR
images, target volumes and OARs as in the optimised plan.
The DVH criteria used for evaluation were EQD2 D90 for HR-
CTV, D2cm³ for rectum, D2cm³ for bladder, D2cm³ for sigmoid
and D2cm³ for bowel.
Results
All HR-CTVs with volumes <40cm 3 were covered with
>90Gy EQD2 for the standard as well as the optimised
plans. For 10 patients the standard plan coverage even
exceeded 100Gy EQD2. In the optimised plans the dose to
OAR could be decreased for 17 patients while still
maintaining the target coverage .
For larger tumours, HR-CTV >40cm3, the dose coverage
decreased with standard plans while the optimised plans
maintained excellent dose coverage for all plans. With
optimisation a good target coverage was obtained at the
cost of an increased but acceptable OAR dose.
Conclusion
In comparison to standardised plans, MRI-based 3D IGABT
planning substantially improved target coverage for larger