ESTRO 36 Abstract Book

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S197 ESTRO 36
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magnetic resonance imaging (MRI) scans reviews were
carried out blind to the clinical data with focus on
radiological parameters potentially correlated to the risk
of VVF (necrosis, tumor height of bladder involvement,
tumor volume). Times were calculated from the date of
diagnosis. Survival were estimated using the Kaplan-Meier
method and the Cox proportional hazards model.
Results
Seventy-one patients were identified. Bladder invasion
was diagnosed either on imaging in 59% or
endoscopically/histologically proven in 41%. All patients
received pelvic external beam radiotherapy (EBRT), 45 Gy
in 25 fractions ± nodal boost to macroscopically involved
lymph nodes. Nineteen of the 21 patients with para-aortic
nodal metastases received para-aortic EBRT. Concurrent
platinum-based chemotherapy (CT) was used in 76%,
neoadjuvant CT was used in 14%. After EBRT, 64 patients
(90%) received uterovaginal BT (low-dose rate in 48%,
pulsed-dose rate in 52%). Eight patients had VVF at
diagnosis. Among the 63 patients without VVF at diagnosis,
14 patients (22.2%) developed VVF later on: four before
(28.6%) and ten (71.4%) after BT (median time to onset:
3.5 months after the start of EBRT). Twelve of the 22
patients (54.5%) who presented VVF, either at diagnosis or
during follow-up, needed surgery (urinary or bowel
diversion ± pelvectomy). Estimated OS, PFS and LCR at 2
years were 57.3% (44.9-68.8), 45.0% (32.3-58.5) and 69.1%
(54.4-80.7) respectively. Presence of para-aortic nodal
metastases was significantly associated with poorer OS on
multivariate analysis (HR=4, p<0.001). Only the presence
of necrosis in the anterior part of the tumor on baseline
MRI was strongly associated with the risk of subsequent
VVF (57% vs O% at 1 year, HR=16.7, p=0.011 on a
multivariate analysis taking into account the tumor
volume). No correlation was found between bladder dose
and risk of VVF.
Conclusion
A curative intent strategy including BT as part of local
treatment is feasible in patients with bladder invasion,
with a rate of 22% of post-treatment VVF. MRI has a strong
predictive value of VVF occurrence. This result has to be
confirmed in an independent cohort. Prognosis remains
poor in regard to lower-staged lesions, with a high risk of
out-of-field failure. Intensification of systemic therapies
should be considered.
OC-0367 Dose-response curve for vaginal stenosis.
Final results of a prospective study.
M. Federico1, A. Tornero2, S. Torres2, B. Pinar1, M. Rey
Baltar1, M. Lloret1, P. Lara1
1Hospital Universitario de Gran Canaria Dr. Negrín,
Radiation Oncology, Las Palmas de Gran Canaria- Ca,
Spain
2Hospital 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 (R2=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 (R2 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).