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ESTRO 36 2017
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Conclusion
Five-year clinical outcome of MR-guided HDR-BT boost is
encouraging, providing excellent disease control and lack
of serious late side effects. A slight decline in long-term
urinary QoL was observed.
PO-0932 Prostate-specific Antigen bounce in patients
treated with 125I prostate brachytherapy: Keep calm
A. Pires
1
, D. Moreira
1
, C. Castro
1
, A. Oliveira
1
, J.
Oliveira
2
, L. Trigo
3
1
Instituto Português de Oncologia do Porto Francisco
Gentil- EPE, Radioncology, Porto, Portugal
2
Instituto Português de Oncologia do Porto Francisco
Gentil- EPE, Urology, Porto, Portugal
3
Instituto Português de Oncologia do Porto Francisco
Gentil- EPE, Brachytherapy, Porto, Portugal
Purpose or Objective
Permanent low-dose-rate brachytherapy (BT) with
125
I is
an established curative modality for the treatment of
localized prostate cancer. After treatment, prostate-
specific antigen (PSA) level may fluctuate and temporarily
increase without a clear reason. This phenomenon is
called “PSA bounce” (PSAb) and often causes anxiety in
patient and physician. Our aim was to analyse the kinetics
of PSA in our patients and the association between PSA
bounce and the long term disease outcome after prostate
BT with
125
I.
Material and Methods
We analysed 134 patients treated with
125
I implantation
monotherapy between 2004 and 2006 in a single
institution. All patients had tumour stage T1-T2cN0M0,
Gleason score ≤ 7 and follow-up time was ≥ 9 years.
Patients who received neo-adjuvant hormone
therapy were excluded. PSAb was defined as a rise
beyound 0.2 ng/ml the initial PSA nadir with a subsequent
decline to or below the initial nadir without treatment.
Biochemical failure (BF) was determined using the Phoenix
definition (nadir +2 ng/mL). Associations between PSAb
and the various pre and post-treatment factors were
assessed with logistic regression analysis, the association
between a PSAb and BF was examined with the
log-rank
test and the
Mann-Whitney U
test was applied to test for
difference in the time to a PSA rise between PSAb and BF
patients.
Results
PSAb occurred in 53 (39,8%) patients with a median time
to bounce of 18,8 months. Only 7 (13,2%) patients with
PSAb developed BF, in contrast to 12 (15%) patients
without previous bounce (p = 0,084). Among the pre and
post-treatment factors, only younger age predicted a PSAb
on a multivariate analysis (p = 0.049). PSA levels during
the bounce reached levels as high as 8,85 ng/mL in this
cohort. BF occurred in 19 patients (14,4%). The 9-year
overall survival rate was 83,6%, the 9-year disease-specific
survival was 95,8% and the rate of survival at 9-year
freedom from BF was higher than 90%.
Conclusion
PSAb is a common finding in our population and is
associated with a lower rate of subsequent BF. Patients
should be advised for the eventual PSAb after
permanent
125
I prostate BT. Those who experience a PSAb
are more likely to be younger. The physicians involved in
patients follow-up after prostate BT should also be aware
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