ESTRO 36 Abstract Book

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S514 ESTRO 36 2017
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applicators were inserted, cone beam computed
tomography (CT) images were obtained. Rectal gas was
observed in 11 brachytherapy fractions from 8 patients.
After draining rectal gas with a Nelaton catheter, cone
beam CT images were obtained again. Brachytherapy was
prescribed to point A using standard two-dimensional
dosimetry and planning. To quantify the dose delivered to
the rectum and urinary bladder, three-dimensional dose
distributions were calculated using the images from
before and after draining rectal gas. The dose to the
rectum and urinary bladder was evaluated based on dose-
volume histograms. The influence of the volume of
discharging rectal gas (pre-draining rectal volume – post-
draining rectal volume) on the rectal dose was
investigated. The minimum doses to the maximum
exposed 0.1, 1 and 2 cc (D 0.1cc, D1cc and D2cc) volumes were
evaluated using the dose from point A. Statistical analyses
were conducted using the paired t-test and a linear
regression model.
Results
The mean rectal dose after draining rectal gas was
significantly lower than that before draining. The rectal
doses (D0.1cc, D1cc and D2cc) relative to point A at post-
draining vs. pre-draining were as follows: 106.9% vs.
121.2%, 88.3% vs. 98.6% and 81.5% vs. 90.9%, respectively
(p<0.05). The mean urinary bladder dose was not
significantly different after draining rectal gas from
before. The urinary bladder doses (D0.1cc, D1cc and D2cc)
relative to point A at post-draining vs. pre-draining were
as follows: 136.0% vs. 133.2%, 112.3% vs. 111.8% and
103.3% vs. 102.4%, respectively. The volume of
discharging rectal gas slightly correlated with the rectal
dose at D 0.1cc (R2=0.45); however, no significant
correlation was found for D 1cc or D2cc (R2=0.10 and -0.01,
respectively).
Conclusion
Our data suggested that draining rectal gas is useful for
reducing the rectal dose in high-dose-rate brachytherapy
for gynecological cancer.
PO-0937 HDR image-guided interstitial brachytherapy
for postoperative local recurrent uterine cancer
K. Yoshida1, H. Yamazaki 2, T. Takenaka2, T. Kotsuma3, K.
Masui2, T. Komori1 , T. Shimbo1, N. Yoshikawa1, H.
Yoshioka1, Y. Uesugi4, T. Hamada1, M. Nakata1, H.
Matsutani1, M.M. Ueda3, Y. Tsujimoto3, E. Tanaka 3, Y.
Narumi1
1 Osaka Medical College, Radiology, Takatsuki, Japan
2 Kyoto Prefectural University of Medicine, Radiology,
Kyoto, Japan
3 National Hospital Organization Osaka National Hospital,
Radiation Oncology, Osaka, Japan
4 Kansai University of Welfare Sciences, Rehabilitation
Sciences, Kashiwara, Japan
Purpose or Objective
In order to evaluate the usefulness of high-dose-rate (HDR)
image-guided interstitial brachytherapy (ISBT) for
postoperative local recurrent uterine cancer, we analyzed
our clinical experience.
Material and Methods
We investigated 48 patients treated with HDR-ISBT at
National Hospital Organization Osaka National Hospital
and Osaka Medical College between May 2003 and January
2014. All patients received radical surgery and 10 patients
also received post-operative radiotherapy as previous
treatments. Histologic finding was squamous cell
carcinoma (SCC), endometrioid adenocarcinoma (AD),
mucinous adenocarcinoma (MAD) and the others
(serous/adenosquamous/endocrine/undifferentiated) for
20, 17, 5 and 6 patients. The median maximum tumor
diameter was 25 mm (range; 5-79 mm). In 38 patients who
had non-irradiation history, 23 patients also received
external beam radiotherapy (EBRT). The median ISBT
doses were 54 Gy in 9 fractions as monotherapy and 30 Gy
in 5 fractions as combination of EBRT. In 10 patients who
had irradiation history, lower doses (36 to 48 Gy in 6 to 8
fractions) were selected. We implanted 7–16 (median, 13)
applicators under transrectal ultrasonography guidance.
We used free-hand implantation with ambulatory
technique for later 42 patients. Magnetic resonance
imaging (MRI)-assisted image-based treatment planning
was also performed. Clinical target volumes (CTV) were
the gloss tumor volume with or without 10 mm of vaginal
margin for patients with or without non-irradiation
history.
Results
The median follow-up time was 41 months (range; 4-115
months). The median D90(CTV)s were 91.3 Gy and 75.6 Gy
for patients with or without non-irradiation history. The 4-
year local control and overall survival rates were 78% and
67% for all patients. The 4-year local control rates were
83% and 60% for patients with or without non-irradiation
history (p=0.02). Tumor diameter, primary site and
histology were not significant prognostic factors of local
control. The 4-year overall survival rates were 73, 65, 100
and 20% for SCC, AD, MAD and the others (P=0.06). The
D90(CTV)s were 93.5±24.3 Gy and 81.4±9.2 Gy for local
control and failure patients (p=0.1). Grade ≥3 late
complications occurred in 11 patients (23%). Ileus was only
observed for patients receiving EBRT.
Conclusion
Our treatment result of image-guided HDR-ISBT showed
good local control result. However, previous irradiation
history was a worse prognostic factor of local control.
Dose-volume histogram seems to be useful for dose
prescription.
PO-0938 Should we use point A dose for image-guided
adaptive brachytherapy reporting in cervix cancer?
R. Mazeron 1, I. Dumas2, A. Escande1, W. Bacorro1, R.
Sun1, C. Haie-Meder1, C. Chargari 1
1Institut Gustave Roussy, Radiation Oncology, Villejuif,
France
2Institut Gustave Roussy, Medical Physics, Villejuif,
France
Purpose or Objective
The recent ICRU report 89 recommends continuing the
reporting of point A dose in the era of Image-guided
adaptive brachytherapy (IGABT). The study aim was to
evaluate the interest of such recommendation by testing
the value of point A as a surrogate of volumetric
dosimetric parameters and as a predicting factor of local
control.
Material and Methods
The dosimetric data from patients treated with a
combination of chemoradiation and intracavitory image-
guided adaptive brachytherapy were confronted to their
outcomes. Prescribing followed the GEC-ESTRO
recommendations. Point A was used for reporting, without
specific planning aim. All doses were converted in 2-Gy
equivalent, summing brachytherapy and EBRT doses. The
relationships between the D90 CTV HR and CTVIR and point A
doses were studied. Dose-effect relationships based on the
probit model and log-rank tests were assessed using the
different dosimetric parameters.
Results
Two hundred and twelve patients were included with a
median follow-up of 53.0 months. MRI guidance was used
in 89.6% of the cases. A total of 28 local relapses were
reported resulting in a local control rate of 86.6% at 3
years. Mean D90 CTVHR, D90 CTV IR and point A doses were
respectively: 79.7±10.4 Gy, 67.4±5.8 Gy and 66.4±5.6 Gy.
The mean D90 CTVHR and CTVIR were significantly different
from the mean point A dose (p=p<0.0001, and 0.022
respectively). Both D90 CTV were independent from point
A doses, even in bulky (width >5cm) tumors at diagnosis or
in large CTVHR lesions (≥ 30cm3) Whereas significant
relationships between the probability of achieving local