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S979
ESTRO 36
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Purpose or Objective
To retrospectively evaluate the incidence, magnitude,
and dosimetric impact of any air pockets between the
vaginal cylinders and the vaginal mucosa using CT-scan
images.
Material and Methods
120 postoperative vaginal cuff brachytherapy cases were
analyzed for receiving the prescribed dose to 5 mm depth
from the cylinder wall. CT-Based treatment planning was
performed in each fraction. The incidence, vaginal
mucosa displacement and air volume were assessed in
each treatment. A Monte Carlo study has also been done
to evaluate the dosimetric effect of air pockets around the
vaginal cylinder.
Results
In 50 patients, a total of 90 air pockets were observed in
150 procedures. Four patients had pocket free insertion
during the whole treatment sessions. The volume of air
pockets ranged between 0.01 cm3 and 4.5 cm3 with
average value of 2.5cm3, and the maximum displacement
of vaginal mucosa from cylinder surface was between 0.2
and 2 cm with average value of 0.8cm. Thirty patients had
no air pockets on their first fraction but in subsequent
fractions. Twenty patients had incorrect applicator
insertion as they have an air gap between applicator tip
and cylinder dome ranged between 0.3 cm and 1.1 cm with
average value of 0.8 cm. The Monte Carlo dosimetry also
shows that the average dose reduction to the vaginal
surface and 5mm-depth, at the air pocket, is respectively
about 9.2% and 7.3% per 1 mm of the air thickness.
Conclusion
Air pockets between vaginal cylinder and the vaginal
mucosa are observed in the majority of treatment
fractions, and the probability of occurrence varies from
patient to patient and procedure to procedure. The dose
reduction effect of air pockets needs to be considered
especially around the vaginal cuff using imaged based
treatment planning in each fraction and the effect on the
clinical outcome should be put under more investigation.
EP-1782 Effect of the amount of bladder filling on
normal tissue doses in 3D-HDR vaginal vault
brachytherapy
I. Er
1
, S. Kınay
1
, R. Kandemir
1
, F. Obuz
2
, A.N. Demiral
1
1
Dokuz Eylul Univ. Health Sciences Institute, Radiation
Oncology, IZMIR, Turkey
2
Dokuz Eylul Univ. Health Sciences Institute, Radiology,
IZMIR, Turkey
Purpose or Objective
In this retrospective study, it was aimed to compare the
dose volume parameters of organs at risk for the bladder
filling of 50 cc versus 150 cc in high dose rate (HDR) three-
dimensional (3-D) vaginal cuff (VC) brachytherapy (BRT).
Material and Methods
The dosimetric data of the 8 hysterectomized patients
with
gynecological
malignancy
who
received
postoperative pelvic external radiotherapy (RT) + 3-D HDR
VC-BRT between March 2015 and August 2015 were
analyzed. Computerized tomography (CT) sectional
images obtained for VC BRT treatment planning were used
for the study. The proximal 1/3 portion of vagina, drawn
as a layer of 0.5 cm thickness from the vaginal mucosa
(cylinder surface), had been delineated as clinical target
volume (CTV). A total dose of 18 Gy (3x6Gy) had been
prescribed to the CTV. For the study, bladder, rectum,
sigmoid, bowel and CTV were recontoured in a 3-D manner
by the same radiation oncology resident. Then the
contours were controlled and corrected first by a staff
radiation oncologist and then a staff radiologist.
Afterwards, treatment planning was performed by the
medical physicist using BRT treatment planning system.
Mean CTV dose-volume parameters (D90%, D100%,
D50%/D90%, V100%, V150%) for all patients were similar in
the treatment plans for two different bladder fillings.
Bladder V50%, D50% and D2cc, rectum D2cc, sigmoid D2cc,
bowel D50% and D2cc were recorded from the dose-
volume histograms obtained in the treatment planning
system. Paired comparisons were made for the parameters
above for the bladder filling of 50 cc versus 150 cc.
Different bladder fillings were compared using Wilcoxon
Signed-Rank Test in the SPSS 15.0 statistics program.
Results
It was observed that as the amount of bladder filling
increases, bowel is displaced cranially from the
applicator. Bladder D50% decreases (p=0.012) while
bladder D2cc increases (p=0.025) in case of 150 cc bladder
filling instead of 50 cc. Rectum D2cc shows a statistical
trend for increase (p=0.05), however bowel D50%
decreases (p=0.012) in 150 cc bladder filling compared to
50cc.
Conclusion
The statistically significant decrease in bladder and
especially bowel D50% parameters supports filling bladder
with 150 cc instead of 50 cc in 3D VC-BRT.
EP-1783 Acute toxicity with Xoft Axxent Electronic
Brachytherapy (XB) in endometrial or cervical cancer
A. Mendez Villamon
1
, A. Miranda Burgos
1
, M. Gascón
Ferrer
1
, M. Puertas Valiño
1
, S. Lozares Cordero
2
, A.
Gandia Martinez
2
, J. Font Gomez
2
, M. Tejedor Gutierrez
1
1
H.U. Miguel Servet, RADIATION ONCOLOGY, Zaragoza,
Spain
2
H.U. Miguel Servet, MEDICAL PHYSICIST, Zaragoza, Spain
Purpose or Objective
To analyze acute toxicity outcomes after treatment with
Xoft Axxent Electronic Brachytherapy (XB) in postsurgical
endometrial or cervical cancer patients treated at our
medical centre.
Material and Methods
Prospective study in which we selected 29 patients that
received treatment with Xoft Axxent Electronic
Brachytherapy (XB) administered twice a week after
endometrial or cervical cancer surgery, with 3D
planification. The patients were selected from September
2015 to September 2016. They were divided in two groups:
Group 1 (15/29) considered high risk and group 2 (14/29)
considered intermediate risk. Group 1 received external
beam radiotherapy (46Gy) followed by XB (15Gy in 5Gy
fractions) and group 2 received exclusive XB (25Gy in 5Gy
fractions). We analyzed the median dose in bladder,
rectum and sigmoid D2cc, V50, V35 with XB comparing the
doses with Ir-192. The vaginal mucosa, gastrointestinal
(GI) and genitourinary (GU) toxicities were analyzed with
the Common Terminology Criteria for Adverse Events
(CTCAE 4.0) scale.
Results
The median dose in bladder with XB vs. Ir-192 was: 2cc
66,4% vs. 71.6%, V50 7,2 vs. 11.9 Gy, V35 14.8 vs. 26,6. In
rectum XB vs. Ir-192 was: D 2cc 68,4% vs. 73.5% , V50 9.9
vs. 16.7 Gy, V35 19.9 vs. 36. In sigmoid XB vs. Ir-192 was:
D 51.4%vs. 59.8%, V50 12.9 vs. 21.3 Gy, V35 28.8 vs. 41.5.
The median follow-up was six and a half months (range 3-
12 months).
In group 1, acute vaginal mucositis (G1) was observed in
40% of the patients, GI toxicity (G1) occurred in 13% and
GU toxicity (G1, G2, G3) was not present.
In group 2, we observed acute vaginal mucositis (G1 and
G2) in 57% of the patients, GI toxicity (G1) occurred in 7%
and GU toxicity (G1) was present in 29%. There was no
grade 3 or greater toxicity in any of the groups. At 3
months follow-up, all of the patients were asymptomatic.
Conclusion
The dose received by the organs at risk with the Xoft
Axxent Electronic Brachytherapy is less compared to Ir-