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S196
ESTRO 36 2017
_______________________________________________________________________________________________
2
Hospital Universitario de Gran Canaria Dr. Negrín,
Radiación Physics, Las Palmas de Gran Canaria- Ca, Spain
Purpose or Objective
Vaginal stenosis as consequence of cervical cancer BT
treatment severely impact quality of life. No dose
constraints have been published so far.
Aim of this study is to identify a threshold level for volume
packing and a dose response curve for vaginal stenosis.
Material and Methods
211 consecutive cervical cancer patients treated between
2008-16 (median FU time 42.4 months) with a median age
at BT of 52.6 years (range 23.7- 88.5) were considered. All
pts received 3DRCT (45-50 Gy with weekly concomitant
CDDP 40 mg/m2 when feasible) and tandem ovoids HDR BT
(or intracavitary-interstitial cylinder application when
needed). Patients received simulation CT scan with
radiopaque vaginal tube in place in order to delineate
vagina from a plane tangential to lower border of pubic
bone up to fornix. At BT vaginal packing (VP) was
contoured from a plane tangential to lower border of
pubic bone up above ovoids surface. Vaginal walls were
delineated as a 2 mm expansion of packing subtracted of
packing volume. 85 pts. (group A) received CT based BT (5
fractions of 5,5 Gy), 126 patients (group B) received MR
based BT (4 fractions of 7 Gy). Group A pts had a
treatment slightly optimized to OARs. Group B pts had a
treatment optimized to OAR and HRCTV according GEC
ESTRO recommendations. All patients entered prospective
follow up. Morbidity was scored according CTCAE 4.0
vaginal volume was also measured with appropriate
vaginal cylinders (diameters 10 to 45 mm).To assess the
relationship between vaginal stenosis, VP and vaginal dose
a median VP volume (VPm) among the 5 (group A) or 4
(group B) application each patient received was
calculated. Moreover the cumulative EBRT+BT EQD2 dose
to vagina was calculated. A Logistic model (LM) was used
to analyze data.
Results
Results are summarized in Tab1. In 929 applications a
double exponential fit was noticed between vaginal dose
and VP volume, with a fast growing exponential part
(minimal variations in VP volume corresponding to huge
variations in vaginal dose), and a slow growing exponential
part (variation in VP volume have modest impact on dose).
VP volume cut off values dividing the two parts of the
curve for all considered vagina DVH parameters were
encompassed between 75 and 80 cc.
LM showed good correlation (R
2
=0.97 and 0.96
respectively) between VPm and G3 or G2-3 vaginal
stenosis (Fig1 A_B). Risk of vaginal stenosis G3 or G2-3 was
less than 10% when a VPm volume >82 or 105cc was
obtained. A dose response curve was found for G3 or G2-3
stenosis and vaginal EBRT+BT EQD2 D80 (R
2
0.99 and 0.98
respectively) with a risk of G3 or G2-3 stenosis lower of
10% when EQD2 dose parameters was lower than 63 and
44Gy EQD2 respectively (Fig1 C-D).
Conclusion
At our knowledge this is the first report finding a
correlation between vaginal stenosis, VP volume and
vaginal dose on a relatively large serie. Further studies on
larger dataset are needed to confirm such data
OC-0368 Postoperative vaginal brachytherapy: a
quality assurance dummy-run procedure in the
PORTEC-4 trial
R. Nout
1
, E. Astreinidou
1
, M. Laman
1
, C. Creutzberg
1
1
Leiden University Medical Center LUMC, Department of
Radiotherapy, Leiden, The Netherlands
Purpose or Objective
As part of the quality assurance program in the ongoing
randomized multicenter PORTEC-4 trial a ‘dummy-run’
procedure for vaginal brachytherapy was mandatory
before centers could participate. The aim was to evaluate
whether the CT- or MRI based clinical target volume (CTV)
and organ at risk (OAR) delineations and the standard
treatment plans were according to the trial protocol,
especially since for many centres this involved
introduction of CT-based delineation and planning for
vaginal brachytherapy.
Material and Methods
Pelvic CT and MRI scan of a postoperative endometrial
cancer patient with a cylinder in situ were made available
to participating Dutch centers. Centers were asked to use
their own treatment planning and delineation software
and follow the study protocol in order to: 1) delineate CTV
and OAR’s: bladder, rectum, sigmoid and small bowel; 2)
reconstruct the single line source path; 3) create a
treatment plan prescribing 7 Gy at 5 mm from the surface
of the applicator (point A2, fig 1); 4) perform DVH
analysis. The CTV consisted of the proximal 4 cm of the