ESTRO 36 Abstract Book

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S519 ESTRO 36
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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. Mazeron1, I. Dumas2 , A. Escande1, W. Bacorro 1, R.
Sun1, C. Haie-Meder1, C. Chargari1
1 Institut Gustave Roussy, Radiation Oncology, Villejuif,
France
2 Institut 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 D 90 CTVHR 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, D 90 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 D 90 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
control and the D90 CTVHR and CTVIR (p=0.08 and 0.025
respectively) were observed, no significant relationship
between point A dose and local control probability could
have been established (Figure). Moreover, a trend towards
an inverse relation was observed. After sorting patients
according to 3 levels of doses, highest local control rates
werereported in patients with D90 CTVHR ≥85 Gy, whereas
the patients with point A doses ≥ 70 Gy had the worst
outcomes.
Conclusion
In patients treated with IGABT, point A dose is not
predictive of local control, and nor correlated to D 90. It
tends to be inversely related to D90 and therefore to be a
surrogate of the irradiated volume. The pertinence of
reporting point A dose should be questioned.
PO-0939 Comparison of brachytherapy sources of
endometrial cancer: Electronic brachytherapy source
and 192Ir
S. Lozares1, J.A. Font Gómez1, A. Gandía Martínez1, A.
Miranda Burgos2, A. Méndez Villamón 2
1Hospital Universitario Miguel Servet, Medical Physics
and Radiation Protection Department, Zaragoza, Spain
2Hospital Universitario Miguel Servet, Oncologic
Radiotherapy Department, Zaragoza, Spain
Purpose or Objective
To compare 29 endometrial cancer patients treated in our
center with cylindrical applicators and Axxent (Xoft Inc.)
electronic brachytherapy with an equivalent planning
made for Ir-192 source.
Material and Methods
29 patients previously treated with Axxent (50 kV source)
have been replanned with Ir-192 source. The calculation
for both types of sources were performed on BrachyVision
(Varian Inc.) treatment planning system.
The prescription was 5 Gy per fraction applied in 3
fractions or 5 fractions depending on previous
radiotherapy treatment.
The planning parameters of the planning target volume
(PTV) countoured from the cylinder surface to 5 mm along
the active length were evaluated. V150 and V200 data for
PTV and D2cc, V50% and V35% for organs at risk (OAR) were
evaluated, the percentage of the volume receiving 35%
and 50% of the prescription dose, respectively, and D2cc,
highest dose to a 2 cubic centimetre volume of an OAR.
Results for bladder, rectum and sigmoid are showed.