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There is little existing data guiding urethral dose
constraint but study in peri-urethral cancer has
demonstrated a higher risk of urethral toxicity in patients
with a urethral EQD2 of >85Gy. Our median EQD2 was
below this level but with a wide range, indicating the
degree of adaptation using image guidance. Given the
poor correlation of applicator angle and length with dose
to OARs choice of applicator should remain dictated by the
patients’ anatomy.
PO-0934 Brachytherapy as part of the conservative
treatment for primary and recurrent vulvar carcinoma
C. Chargari
1,2
, P. Castelnau-Marchand
1
, A. Escande
1
, I.
Dumas
1
, R. Mazeron
1
, P. Maroun
1
, E. Bentivegna
3
, S.
Gouy
3
, A. Cavalcanti
3
, P. Morice
3
, C. Haie-Meder
1
1
Gustave Roussy Cancer Campus, Brachytherapy unit-
Radiation oncology, Villejuif, France
2
French Military Health Services Academy, French
Military Health Services Academy, Paris, France
3
Gustave Roussy Cancer Campus, Department of Surgery,
Villejuif, France
Purpose or Objective
There are only scarce data on the place of brachytherapy
(BT) for treatment of vulvar carcinoma. Our institutional
experience of interstitial BT for vulvar carcinoma patients
is reported.
Material and Methods
Clinical records of patients receiving low-dose rate (LDR)
or pulsed-dose rate (PDR) BT as part of the primary
treatment for primary/recurrent vulvar squamous cell
carcinoma or as part of adjuvant treatment between 2000
and 2015 were included. Patients, tumors and treatments
characteristics as well as clinical outcome were examined.
Results
A total of 26 patients treated with BT were identified. BT
was delivered as part of primary intent treatment for
locally advanced/recurrent cancer in 11 patients, and as
part of adjuvant treatment in 15 patients. Median age at
time of BT was 63 years (range: 41 – 88 years). PDR and
LDR were used in 15 patients and 11 patients,
respectively. BT was performed as a boost to the tumour
bed following EBRT (n=13) or as only irradiation modality
(n=13). Total median dose at the level of primary tumor
was 60 GyEQD2 (range: 55 – 60 GyEQD2). With mean
follow-up of 41 months (range: 5 months – 11.3 years), 11
patients experienced tumour relapse. Ten patients
experienced local relapse as first event, associated with
synchronous extra-vulvar events in 8/10 patients. Three-
year estimated disease-free survival and overall survival
rates were 57% (95%CI: 45–69%) and 81% (95%CI: 72-90%).
All toxicities were grade 2 or less.
Conclusion
Interstitial BT used as part of the primary or adjuvant
treatment of vulvar carcinoma is feasible with a
satisfactory toxicity profile. Prognosis remains however,
dismal, with a high frequency of local and distant failures
in patients with locally advanced tumors.
PO-0935 Modeling to compensate for intra-fractional
bladder dose variations in gynecological brachytherapy
Z. Siavashpour
1
, R. Jaberi
2
, M.R. Aghamiri
1
, C. Kirisits
3
1
Shahid Beheshti University, Medical Radiation
Engineering, Tehran, Iran Islamic Republic of
2
Tehran University of Medical Sciences, Radiotherapy,
Tehran, Iran Islamic Republic of
3
Comprehensive Cancer Center- Medical University of
Vienna, Department of Radiotherapy and Oncology,
Vienna, Austria
Purpose or Objective
Proposing a model to compensate for intra-fractional
bladder dose variations during gynecological (GYN)
brachytherapy.
Material and Methods
Thirty advanced cervical cancer patients treated with HDR
(
192
I source) intracavitary brachytherapy were selected.
Rotterdam applicators (tandem-ovoids) were used for
them. Patients pelvic CT scans were done twice; pre- and
post-treatment (about 30 min after dose delivery), with
applicator in situ. Flexiplan
®
(version 2.6, Isodose control,
the Netherlands) as a 3D treatment planning software was
used. Applicator reconstruction and organs delineation
were done by the same physicist /physician on both image
sets. Totally identical plans (dwell times/positions) were
applied to both image sets and DVH parameters were
recorded; planning aims: 80-90 Gy (EQD2) for D
90
of CTV
HR
and less than 85, 75, and 75 Gy for D
2cm³
of bladder,
rectum, and sigmoid, respectively.
RT-Structure files (in DICOM format) of the patients for
whom intra-fractional dose (D
2cm³
) variations were higher
than 5% were exported from planning system. Applicator-
organs distances along the active length of three
applicators were extracted by some in-house MATLAB
written codes. Source dwell times were extracted from
treatment planning report files (in xps format). A model
was design to propose new source dwell times to
compensate for the bladder wall to applicators walls
distances intra-fractional variations, considering the TG43
algorithm and inverse square law. Some dwell times
acceptance criteria were considered during modeling such
as: D
90
of CTV
HR
and CTV
IR
have not changed to be less than
85 Gy 70 Gy, respectively. New dwell times were applied
to the plans to test their influences on DVH parameters.
Also, the model was further optimized to reduce the
executing time by searching for the most impressive part
of the applicators lengths on bladder dose.
Results
For one third of the considered patients bladder dose
changes were higher than 5%. Mean ± SD of D
2cm³
intra-
fractional relative changes ((D
2cm³(before)
- D
2cm³(after)
)/
D
2cm³(before)
× 100) of these ten cases were 19.3 ± 18.0 %.
After correcting the plans these variations became 10.5 ±
14.5. More bladder dose correction would lead to a
significant decrease in dose to CTV
HR
and was
unjustifiable. Model runtime was about 3 minutes (Intel
corei7 laptop, RAM = 8 GB, CPU = 2 GHz).
Conclusion
A model was developed to correct the bladder dose to be
as similar as possible to the pre-treatment plan one. It is
a semi-online model that can be used in the routine
clinical workflow to reduce the GYN image-guided
adaptive brachytherapy uncertainties. The model can be
generalized to other organs at risk.
PO-0936 Dose effects of draining rectal gas in image-
guided brachytherapy for gynecological cancer
H. Takase
1
, N. Ii
2
, Y. Yamao
1
, T. Kawamura
2
, M. Naito
1
,
Y. Watanabe
2,3
, Y. Toyomasu
2
, A. Takada
2
, H. Tanaka
2
, T.
Yamada
1
, H. Maki
1
, H. Sakuma
4
, Y. Nomoto
5
1
Mie University Hospital, Department of Radiology, Tsu,
Japan
2
Mie University Hospital, Department of Radiation
Oncology, Tsu, Japan
3
Matsusaka central hospital, Department of Radiation
Oncology, Matsusaka, Japan
4
Mie University Graduate School of Medicine,
Department of Radiology, Tsu, Japan
5
Mie University Graduate School of Medicine,
Department of Radiation Oncology, Tsu, Japan
Purpose or Objective
To verify the usefulness of draining rectal gas in image-
guided high-dose-rate brachytherapy for gynecological
cancer, we quantified the dose delivered to the rectum
and urinary bladder with and without draining rectal gas.
Material and Methods
From October 2013 to July 2014, 116 brachytherapy
fractions from 34 patients were performed in our
department for gynecological cancer. After the