ESTRO 36 Abstract Book

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S376 ESTRO 36 2017
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to late toxicity, there is no significantly difference in late
GI (RR=1.04, 95%CI: 0.88-1.23, p=0.63) and GU toxicity
(RR=1.10, 95% CI: 0.47- 2.40, p=0.26) at 5-years. Since
severe heterogeneity were existed, we also divided these
studies into dose-escalated and no dose-escalate H-RT
group. Dose-escalated H-RT increased in late GI toxicity
(RR=1.80, 95%CI: 1.32-2.43, p=0.0002) and GU toxicity
(RR=1.38, 95%CI: 1.07-1.79, p=0.01) significantly, while no
dose-escalated H-RT did not (GI: RR=0.82, 95%CI: 0.68-
1.00, p=0.05; GU: RR=0.92, 95%CI: 0.72-1.16, p=0.46).
Conclusion
This meta-analysis provides more reliable evidence that H-
RT decreased biochemical failure rate, while did not
improve overall survival. For dose-escalated H-RT also
decreased BCDF rates, and accordingly increased late GI
and GU toxicity, while for those without dose-escalated H-
RT, there is no difference in BCDF and late GI and GU
toxicity.
PO-0725 Sigmoid colon is an important organ at risk
for high-grade faecal urgency after pelvic radiotherapy
R. Jadon1, P. Parsons2, L. Hanna1, M. Evans1, J. Staffurth1
1 Velindre Cancer Centre, Department of Clinical
Oncology, Cardiff, United Kingdom
2 Velindre Cancer Centre, Department of Medical Physics,
Cardiff, United Kingdom
Purpose or Objective
Faecal urgency is a common symptom after pelvic
radiotherapy negatively impacting quality of life for
survivors of pelvic malignancies. Compared with other
symptoms such as rectal bleeding and incontinence, dose-
volume predictors of faecal urgency are not well
established and have not been discussed in the QUANTEC
reviews. In this study dose-volume predictors of faecal
urgency and constraints to potentially prevent it are
sought.
Material and Methods
Patient-reported late bowel toxicity data was collected
for patients treated with pelvic radiotherapy 12 months
post-treatment using the subjective LENT-SOMA patient
questionnaire. Treatment plans for these patients were
retrospectively analysed with contouring of potential
organs at risk including bowel loops, bowel bag, small
bowel, large bowel, sigmoid, rectum and anal canal.
Dose-volume predictors for these organs were sought using
multivariate logistic regression analysis, with a p-value of
<0.05 considered significant. Constraints from these
significant dose-volume predictors were then determined
to dichotomise patients into those with and without faecal
urgency. Chi-squared analysis was used to assess the
'goodness of fit” of these constraints. The constraints were
re-explored on the 24 months post-treatment toxicity data
for the same patients.
Results
203 patients returned questionnaires including 128
prostate and pelvic node patients, 19 bladder patients, 38
endometrium and 18 cervical cancer patients. 73% were
treated with conformal radiotherapy and 27% with IMRT/
VMAT. Faecal urgency was reported by 52% of patients,
with 41% reporting high grade (grade 3-4 toxicity), defined
as 'daily” (grade 3) or 'constantly” (grade 4). There was no
clear difference in urgency rates by diagnosis or
radiotherapy technique used.
Dose volume parameters of bowel loops, large bowel and
sigmoid were predictive of faecal urgency. However only
sigmoid parameters (V10, V15, V25) could be used to
derive statistically significant constraints below which
toxicity would be clinically acceptable. These constraints
are detailed in the table below. At 24 months these
constraints still demonstrated the ability to dichotomise
patients with and without toxicity, although not
statistically significantly.
Conclusion
These results suggest sigmoid colon to be a responsible
OAR for faecal urgency, and reduction of sigmoid dose may
improve faecal urgency rates for pelvic radiotherapy
patients. Further validation of the constraints derived in
an independent sample of patients is required.
PO-0726 Dose escalation with HDR brachytherapy for
intermediate- and high-risk prostate cancer
R. Chicas-Sett1,2,3, F. Celada1, J. Burgos1, D. Farga1, M.
Perez-Calatayud1, S. Roldan1, E. Collado1, B. Ibañez1, J.
Perez-Calatayud1, A. Tormo1
1La Fe Polytechnic and University Hospital, Radiation
Oncology, Valencia, Spain
2Universidad Católica de Valencia "San Vicente Mártir",
Escuela de Doctorado, Valencia, Spain
3Recoletas Oncology Institute- Campo Grande Hospital,
Radiation Oncology, Valladolid, Spain
Purpose or Objective
Dose escalation by the combined therapy between high-
dose-rate brachytherapy (HDRB) plus external beam
radiation therapy (EBRT) has reported excellent clinical
results, strongly supporting its use in high-risk patients.
We present our experience of dose escalation using a
single-fraction HDRB for intermediate- and high-risk
prostate cancer.
Material and Methods
From August 2010 to September 2015, 332 patients with
National Comprehensive Cancer Network intermediate-
(n=59) and high-risk (n=273) prostate cancer were
evaluated. Median age was 71 years (range 46-84). The
staging was performed via magnetic resonance imaging
(MRI) in every case, as is showed in table1. Patients
underwent a single-fraction HDRB boost of 15 Gy (n=242)
or 9-9.5 Gy (n=90) if seminal vesicles were infiltrated using
real-time TRUS based planning. Four gold fiducials
markers were implanted immediately after HDRB. EBRT 46
Gy/23fx or 60 Gy/30fx was performed 4 weeks after HDRB
to patients who received 15 Gy and 9-9.5 Gy HDRB boost
respectively. All patients received EBRT by Volumetric Arc
Therapy (VMAT) with imaging guided by CBCT. A total of
148 patients (45%) received a dose of 46 Gy to the pelvis
according to the risk pelvic node involvement by ROACH
formula. The constraints recommended by GEC/ESTRO
have been respected in all brachytherapy plans (Rectum
D 2cc ≤ 75Gy; urethra D10 ≤120 Gy EQD2). GI and GU
toxicities were reported according to CTAE v4.0. In all,
290 patients (87%) received neo-concomitant and adjuvant
androgen deprivation therapy. Patients were followed
prospectively and the Phoenix definition was used to
assess biochemical failure