ESTRO 36 Abstract Book

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S670 ESTRO 36 2017
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stage 3 disease. This approach has shown to reduce both
local recurrence rates and increase the rate of sphincter
preservation procedures. Up to 20% of patients 6 weeks
post neoadjuvant CRT have a complete histological
response (pCR). PCR has shown to correlate with better
and sustained oncological outcomes. The feasibility of the
emerging watch and wait management strategy for
patients with pCR will depend on the reliability of
restaging assessments post CRT.
We looked the accuracy of pre-operative MRI in predicting
the rectal cancer tumour stage, node status and complete
clinical response in patients who have undergone
neoadjuvant chemoradiotherapy using histopathologic
analysis as the reference standard.
Material and Methods
We retrospectively identified all patients who underwent
neoadjuvant CRT (50.4 Gy, 1.8 Gy/fraction, in 5.5 weeks,
with continuous infusional fluorouracil 225 mg/m2daily)
for rectal cancer and proceeded to standard TME at our
institution over a 16 month period. Their initial cTNM
staging was collected as was their restaging ycTNM post
CRT (based on diffusion weighted MRI pelvis). The
sensitivity and specificity of the latter at predicting
tumour, nodal and complete clinical response compared
to surgical histology was analysed.
Results
43 patients underwent CRT and subsequent TME over the
time period at our institution. Overall histopathological
response rate was 93% with a pCR rate of 14%. MRI had a
sensitivity of 58% and specificity of 94% at assessing
compete clinical response, 95 CI 40-93%, 80-99%
respectively. At predicting tumour response MRI had
sensitivity of 53% and specificity of 85%, 95 CI 45-80%, 74-
94% respectively. Accuracy of predicting nodal response
were lower with a sensitivity of 43% and specificity of 40%
, 95 CI 30-88%,32-58% respectively. The average modal
time interval between CRT and MRI was 5 weeks while the
average modal time between CRT and surgery was 8 weeks
Conclusion
Our study suggests that MRI alone may not be accurate
enough in assessing clinical stage post neoadjuvant CRT,
and particularly the clinical node status. Imaging alone
will likely be needed to be combined with clinical,
biochemical and endoscopic assessments in order to
improve reliability of post treatment rectal staging.
EP-1258 High precision SIB-IMRT versus conventional
radiotherapy in anal cancer: a propensity score
analysis
F. Arcadipane1, A. Lepinoy2, P. Franco1, M. Ceccarelli3, B.
De Bari2 , L. Lestrade2, G. Furfaro1, M. Mistrangelo 4, G.
Créhange5 , U. Ricardi1
1 Radiation Oncology, Oncology, Turin, Italy
2 Radiation Oncology, Radiation Oncology, Besançon,
France
3 Cancer Epidemiology and CPO Piemonte, Epidemiology,
Turin, Italy
4 Surgery, Surgical Sciences, Turin, Italy
5 Radiation Oncology, Radiation Oncology, Dijon, France
Purpose or Objective
To evaluate clinical outcomes of a simultaneous
integrated boost- intensity modulated radiotherapy (SIB-
IMRT) approach in patients with non-metastatic anal
cancer compared to those of a set of patients treated with
3-dimensional conformal radiation and sequential boost
(CRT).
Material and Methods
A retrospective cohort of 190 anal cancer patients
consecutively treated between March 2007 and October
2015 at 2 academic centres with concurrent chemo-
radiation employing either SIB-IMRT or CRT was analysed.
The SIB-IMRT group consisted of 87 patients, treated with
2 cycles of Mitomycin and 5-Fluorouracil using a SIB-IMRT
based schedule of 42-45 Gy/28-30 fractions to the elective
pelvic lymph nodes and 50.4-54 Gy/28-30 fractions to the
primary tumor and involved nodes, based on pre-
treatment staging.
The CRT group comprised 103 patients, treated with
Mitomycin or Cisplatin and 5-Fluorouracil or Capecitabine
concurrent to CRT with 36 Gy/20 fractions to a single
volume including gross tumor, clinical nodes and elective
nodal volumes, and a sequential boost to primary tumor
and involved nodes of 23.4 Gy/13 fractions.
We determined colostomy-free survival (CFS) and overall
survival (OS), loco-regional recurrence and distant
metastases rates for each radiation modality. Cox
proportional-hazards model addressed factors influencing
OS and CFS. Propensity score-matched analyses were
performed to compare SIB-IMRT and CRT.
Results
Median follow-up for the entire patient group was 32
months. Average overall treatment time was 42 days in
the SIB-IMRT group and 59 days in the CRT group. Patients
treated with CRT had significantly higher stage and lower
grading. The overall survival at the time of analysis was
74%, similarly for the two groups. Three-year colostomy-
free survival was 66% for all patients, with no significant
difference between the two groups (61% for SIB-IMRT and
74% for CRT, Log-Rank 0.85). The cumulative incidence of
colostomies showed that the majority of events occurred
within 18 months in both groups. We found no significant
difference in terms of outcomes by univariate analysis and
a propensity score analysis adjusted for disparities
between the groups.
NA:Not Available
Tab. 1 Patient and treatment characteristics and pattern
of failure