ESTRO 36 Abstract Book

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S676 ESTRO 36
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EP-1256 Local ablative radiotherapy for liver
metastasis: factors affecting local control and survival
C. Petersen1, T. Gauer1, T. Frenzel1, M. Todorovic1, A.
Krüll1, M. Blaschczyk1
1 University Medical Center Hamburg - Eppendorf UKE,
Department of Radiation Oncology, Hamburg, Germany
Purpose or Objective
The liver is a common site of metastases from most
common solid malignancies. Currently available systemic
treatment regimens, result in transient to long-term
disease control, raising the question of further local
management. Secondary resection and thermo-ablation
may contribute to long-term survival or allow at least a
relevant chemotherapy-free interval. These approaches
are often limited. With stereotactic body radiotherapy
metastases can be treated with high efficiency in only a
few sessions. Here we evaluate the feasibility of high-dose
stereotactic body radiation therapy for liver metastases in
patients not eligible for surgery focussing on colorectal
cancer patients.
Material and Methods
Between July 2012 and December 2015, 33 patients with
56 liver metastases (range 1-4) were treated with SBRT.
Primary tumor mostly consists of colorectal cancer (59%)
and others (lung-, breast-, pancreatic cancer). Median
time between diagnosis of liver metastases and SBRT was
11 months (range 0-57 months). To receive precise
information about target localization, 3 gold fiducial
markers were implanted in 30 out of 56 lesions (54%). To
analyze respiratory tumor motion, 4D-CT scans were
performed for all patients. Gross tumor volume contours
of 10 breathing cycles were transferred to the average CT
of the CD-CT data, forming the internal target volume
(ITV). Planning target volume was obtained by adding a 4
mm margin. SBRT was delivered in VMAT technique using
Varian TrueBeam linear accelerator. Most common
fractionation schedule was 5 x 11 Gy (90% isodose covering
the PTV).
Results
The median follow-up for all patients was 13 months. The
overall local control rate for all 56 metastases was 86%
with a total of 7 failures. In univariate analysis, the
implantation of fiducial markers was predictive for local
control (p=0.029). During follow up period, tumor
progression developed in 28 cases (83%). In 13 cases new
intrahepatic lesions occurred (47%), in 10 cases extra
hepatic lesions (36%) and in 5 cases intra- and extra
hepatic lesions (18%). Overall survival rate was 58%,
median overall survival was 21 months. Univariate analysis
showed statistical significance for OS concerning histology
(colorectal vs. other) and gross tumor volume (</> 20
ccm).
Conclusion
Liver SBRT is effective and yielded good local control. The
SBRT procedure is a valid option for patients with
oligometastatic disease and should be considered as an
alternative to surgical treatment or other local ablative
techniques.
Electronic Poster: Clinical track: Lower GI (colon,
rectum, anus)
EP-1257 A look at pre-operative MRI accuracy at
predicting rectal cancer staging post
chemoradiotherapy
K. Nugent1, R. McDermott 1, M. Higgins1, B. O'Neill1
1 St Lukes Radiation Network, Radiation Oncology,
Dublin, Ireland
Purpose or Objective
Neoadjuvant chemoradiotherpy (CRT) has become
standard in the treatment of rectal cancer patients with
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. Mistrangelo4, G.
Créhange5, U. Ricardi1
1Radiation Oncology, Oncology, Turin, Italy
2Radiation Oncology, Radiation Oncology, Besançon,
France
3Cancer Epidemiology and CPO Piemonte, Epidemiology,
Turin, Italy
4Surgery, Surgical Sciences, Turin, Italy
5Radiation 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