ESTRO 36 Abstract Book

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S684 ESTRO 36
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54.1%-99.9%), we stratified pts into two subgroups to test
a possible correlation with pCR.
Results
Forty-eight pts were treated from March 2002 to October
2011 [M/F: 32/16; median age: 70.5, range: 43-84]. The
median follow-up was 61.5 months (range: 2-136). Ten pts
achieved a pCR (20.8%). No significant differences were
observed based on Ki67 value (lower Ki67: 62.5% pCR;
higher Ki67: 37.5% pCR); Fisher's Exact test: p=0.345).
One-year, 3-year, and 5-year cumulative DFS were 97.9%,
86.0%, and 79.8%, respectively. One-year, 3-year, and 5-
year cumulative OS were 97.8%, 93.5%, and 84.1%,
respectively (fig.1).
Conclusion
In this retrospective analysis no significant correlation was
observed between Ki67 expression and pCR rate after
preoperative chemoradiation. The small sample size and
heterogeneity in neoadjuvant and adjuvant treatment
could explain this result.
EP-1273 Stereotactic body radiation therapy (SBRT)
for pelvic re-irradiation
Y. Augustin1, C. Chaw1, N. Van As1, K. Aitken1
1 Royal Marsden Hospital Trust & Institute of Cancer
Research, Radiotherapy, London, United Kingdom
Purpose or Objective
Re-irradiation of recurrent pelvic disease remains a
challenging clinical problem. SBRT is an attractive
modality for re-irradiation which is being increasingly
utilised in carefully selected patients. However there
remains uncertainty around clinical toxicity, efficacy and
maximum safe cumulative doses to pelvic organs at risk
(OARs).
The primary aim of this retrospective study was to
evaluate treatment related toxicity in patients receiving
SBRT with the Cyberknife platform for pelvic re-irradiation
at our institution. Secondary objectives were to evaluate
efficacy by analysis of local control (LC), distant
progression free survival (DPFS) and overall survival (OS)
parameters.
Material and Methods
Patients receiving re-irradiation with SBRT to pelvic
targets within a previously irradiated external beam
radiotherapy (EBRT) field were retrospectively identified.
Patients treated with prior pelvic brachytherapy were
excluded. Details on primary site, previous EBRT and re-
irradiation dose, toxicity, local control and survival were
obtained on review of the hospital records. Acute (≤3
months) and late toxicity data were retrospectively
collected and assessed using CTCAE v4.0. Local and distant
progression free survival were calculated from the date of
SBRT to the date of radiological progression using standard
RECIST criteria (v1.1).
Results
22 patients (9 prostate and 13 rectal cancer) received
pelvic re-irradiation with SBRT between 25.07.2011 and
20.04.2016. Median age was 66 years (range 30-85 years).
Median follow up was 18.5 months (range 3-58 months).
The median time between primary EBRT and SBRT re-
irradiation was 26 months (range 4-162 months). Median
SBRT dose was 30Gy/3# (range 24Gy-44Gy/3-5#). Prior
EBRT dose ranged from 20Gy/4#-70Gy/35# (median BED
63.72, range 30-84 assuming α/β = 10).
55% patients reported no measurable toxicity. No patients
experienced ≥Grade 3 toxicity.10/22 (45%) patients
experienced acute Grade 1/Grade 2 toxicities including
fatigue, sciatica, nausea, diarrhoea, rectal haemorrhage
and urinary symptoms. Only 1 patient experienced late
toxicity (asymptomatic pelvic insufficiency at 21 months
post SBRT, not requiring intervention).
The 1 and 2 year LC rate were 90%, 85% and DPFS rate 92%,
71% respectively. OS at 1 and 2 years were 91% and 71%
respectively.
Conclusion
Pelvic re-irradiation with SBRT is well tolerated and
effective at controlling local disease. No ≥Grade 3 toxicity
has been observed to date in our patient cohort although
longer term follow up is needed. Further research to
establish safe maximum cumulative doses to OARs for
pelvic re-irradiation is warranted.
EP-1274 Impact of concomitant radiotherapy boost in
locally advanced rectal cancer: dose escalation
M.A. Estornell1, D. Martinez2, V. Morillo3, M. López1, M.
Soler 1, J.L. Monroy1, A.V. Navarro1, A. Soler-Rodriguez1
1Hospital Universitario de la Ribera, Radiation Oncology
Department., Alzira, Spain
2University Hospital.Valladolid, Department of Medical
Physics and Radiation Protection., Valladolid, Spain
3Provincial Hospital. Castellon., Radiation Oncology
Department, Castellon., Spain
Purpose or Objective
The standard preoperative radiation dose for locally
advanced rectal cancer (LARC) is 45-50.4 Gy in 25-28
fractions. The aim of this study is to analyze the
correlation between escalation radiotherapy dose,
pathological complete clinical response (pCR) and
downstaging rate or even its relation with other
parameters of interest as toxicity, surgical margins,
locoregional recurrence-free survival (LRFSD), distant
metastasis free survival (DMFS) and overall survival (OS).
The efficacy of the dose escalation in terms of
pathological tumor response was evaluated as main end-
point.
Material and Methods
Between 2000 and 2013, 287 patients were treated with
preoperative chemoradiotherapy and surgical resection
for LARC in our hospital. 233 patients underwent the
standard chemoradiation schedule (median age 67 years;
stage III 73.3%, stage IV 1.7%; 41.1% low third rectum; 45-
50.4 Gy; 1.8-2 Gy/fraction) and 54 patients were treated
with simultaneous integrated boost-SIB (median age 66
years; stage III 74.5%, stage IV 1.8%; 21.8 % low third
rectum; 45 Gy to the pelvis volume with a 2.17 Gy SIB on
the tumor and macroscopical nodes).