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of this phenomenon, encouraging them to adhere to
appropriate PSA surveillance and avoiding unnecessary
and repetitive PSA measurements, biopsies and premature
or inappropriate initiation of salvage therapy during PSAb.
Poster: Brachytherapy: Gynaecolgy
PO-0933 Urethral dose in cervical image guided
brachytherapy
K. MacLennan
1
, M. Zahra
2
, W. Keough
2
1
NHS Lothian, ST6, Edinburgh, United Kingdom
2
NHS Lothian, Edinburgh Cancer Centre, Edinburgh,
United Kingdom
Purpose or Objective
Urethral dose is not currently included in the
recommendations for the dose constraints for organs at
risk (OARs). However, combined external beam and HDR
cervical brachytherapy can result in significant urinary
toxicity. We investigated the urethral dosimetry for
patients treated with HDR brachytherapy.
Material and Methods
Retrospective audit of 117 patients undergoing cervical
brachytherapy for cervical cancer in the Edinburgh Cancer
Centre between 2010-2015. Patients were treated with
45Gy/25 fractions EBRT followed by 3 fractions of CT-
guided HDR brachytherapy with a ring and tandem aiming
for D90 between 80-85Gy. The urethra and peri-urethral
tissues were retrospectively contoured 1cm inferiorly from
bladder neck or to the axial slice corresponding to the
metal connector of ring and tandem device (whichever
most inferior). Dose volume histograms were used to
determine the urethral D2cc and expressed as 2Gy
equivalent (EQD2) using an a/b ratio of 3. A combined
EQD2 dose for external beam and HDR treatment was
calculated. Data was also collected on the length and
angle of the tandem applicator and a paired T-test with
0.05 significance level was used to assess the effect of the
angle or tandem length on the urethral dose.
Results
117 patients aged 21-84. A 30º applicator angle was used
in 12% cases, 45º in 67%, 60º in 21% patients. A 6 cm
applicator was used in 68% patients; 4cm in 32% patients.7
patients had a single fraction of HDR brachytherapy and
converted to a CT planned phase 2 with external beam
radiotherapy. Excluding the phase 2 patients, median
combined dose to HRCTV was 84.03 Gy and to the urethral
d2cc was 50.7Gy (range: 44.8- 173.9Gy)
Comparing the maximum EQD2 to 2cm
3
urethra from the
fractionated treatment by applicator angle and length;
Tandem
Applicator
Angle
30º Tandem
45º Tandem
60º Tandem
Maximum
EQD2 per
fraction to
2cm
3
urethra
Median 1.52 Gy
(range 0.94-4.90)
Median 3.63 Gy
(range 0.70-
60.98)
Median
3.262 Gy
(range 0.76-
23.67)
Total EQD2
2cm
3
urethra 3
fractions HDR
BT
Median 3.59 Gy
(range 1.59-12.30)
Median 8.07 Gy
(range 1.82-
130.75)
Median 6.89
Gy
(range 2.14-
52.81)
T test for angle (30º vs 45º, 45º vs 60º and 60º vs 45º)
suggested a difference in urethral dose using a
30º applicator, with a tendency for lower urethral D2cc
with a 30º angle. (30 vs 45 p = 0.002 and 30 vs 60 p =
0.04).
There was no difference in urethral dose per HDR
fraction according to applicator length (t-test, p = 0.54).
Conclusion
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.