ESTRO 36 Abstract Book

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S682 ESTRO 36
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Conclusion
The system appears to be able to compensate the
disomogenities due to the presence of magnetic field
through the use of optimizer.
EP-1268 Tumor response according to NK cell change
during preoperative chemoradiotherapy in rectal
cancer
J. Heo1, Y.T. Oh1, O.K. Noh1, M. Chun1, J.E. Park2, S.R.
Cho 3
1 Ajou University School of Medicine, Radiation Oncology,
Suwon, Korea Republic of
2 Ajou University School of Medicine, Pediatrics, Suwon,
Korea Republic of
3 Ajou University School of Medicine, Laboratory
Medicine, Suwon, Korea Republic of
Purpose or Objective
The objective of this prospective study was to evaluate
the relationship between the circulating lymphocyte
subpopulation counts during preoperative
chemoradiotherapy (CRT) and tumor response in locally
advanced rectal cancer.
Material and Methods
In this prospective study, from August 2015 to June 2016,
10 patients treated with preoperative CRT followed by
surgery were enrolled. Patients received conventional
fractionated radiotherapy (50.4 Gy) with fluorouracil-
based chemotherapy. Surgical resection was performed at
4 to 8 weeks after the completion of preoperative CRT.
The absolute blood lymphocyte subpopulation was
obtained prior to and after 4 weeks of CRT. We analyzed
the association between a tumor response and change in
the lymphocyte subpopulation during CRT.
Results
Among 10 patients, 2 (20%) had evidence of pathologic
complete response. In 8 patients with clinically node
positive, 4 (50%) had nodal tumor response. All
lymphocyte subpopulation counts at 4 weeks after CRT
were significantly lower than those observed during
pretreatment (p < 0.01). A high decrease in NK cell count
during CRT (baseline cell count − cell count at 4 weeks)
was associated with node down staging (p = 0.034).
Conclusion
Our results suggest that the change of lymphocyte subset
to preoperative CRT may be a predictive factor for tumor
response in rectal cancer.
EP-1269 Comparison of 2 and 3 arc VMAT versus fixed
field IMRT and proton beam therapy in anal cancer
C. Kronborg1, E.E. Wilken2, J. Hansen 1, L. Nyvang 1, J.B.
Petersen1, E. Serup-Hansen2, K.L.G. Spindler1
1 Aarhus University Hospital, Oncology, Aarhus C,
Denmark
2 Herlev and Gentofte Hospital, Oncology, Herlev,
Denmark
Purpose or Objective
Chemoradiotherapy is the standard treatment for
squamous cell carcinoma of the anus (SCCA) and is the
source of both acute and late toxicity. Advanced
radiotherapy treatment techniques aim at reducing dose
to organs at risk (OAR) while maintaining target coverage
and dose homogeneity. Further, VMAT techniques shorten
delivery time considerably. We compared dosimetric
advantages of fixed field IMRT, 2 and 3 arc VMAT and
additional 3- and 4-field pencil beam scanning proton
therapy.
Material and Methods
Twenty patients with SCCA treated at two different
centres were included. Standard treatment was 64-51,2
Gy/32 F or 60-49,5/30 Gy/F delivered with 2 or 3 arc VMAT
technique and concurrent chemotherapy according to
local practice. Alternative treatment plans were
generated for all patients using 5- or 6- fixed field IMRT
and 3 arc VMAT (All Varian Eclipse planning system). Four
patients with doses above normal constraints (ex high V40
Gy to the bowel) were selected for additional proton
therapy planning; both 3- and 4- field plans were
generated (Eclipse ver. 10 Multi Field Optimization
(IMPT)). Bowel was delineated as potential bowel cavity
and bladder as total circumference.
Results
Target volume coverage and homogeneity were
comparable between the different planning techniques.
We compared multiple dose volume parameters to OAR
including V40 Gy and V50 Gy to the bowel cavity, V45 Gy
to the bladder, mean dose to femoral heads using IMRT, 2
arc VMAT and 3 arc VMAT techniques and found no
significant differences in any parameter. Both 3- and 4-
field proton treatment plans demonstrated significant
sparing on V40 Gy to the bowel cavity: median volume
using 2 Arc VMAT was 667 cc, 3- and 4-field proton therapy
522 cc and 535 cc respectively. V45 Gy to the bladder was
also considerably lower using protons: 2 arc VMAT 49,3%
vs. 23,4% and 28,5% using 3- and 4-field proton therapy.
Mean dose to femoral heads was significantly lower with
proton therapy while V40 Gy and V30 Gy to the sacral bone
were comparable.
Conclusion
We found dosimetric equality on the selected parameters
for OAR when comparing 2 arc VMAT with fixed field IMRT
and 3 arc VMAT, and no differences between 2 and 3 arc
VMAT either. VMAT reduces overall treatment time and is
a feasible option for standard treatment planning in SCCA.
In four patients with high V40 Gy to the bowel proton
treatment plans proved superior in V40 Gy to the bowel,
V45 Gy to the bladder, and mean dose to femoral heads
with the potential to reduce subsequent toxicity. Data on
acute toxicity will be presented at the meeting.
EP-1270 Clinical outcome of non-metastatic rectal
cancer patients with extremely high CEA level
S.H. YOUN1, D.Y. KIM1, T.H. KIM1, S.Y. KIM2, J.H. BAEK 2,
Y.J. CHA2, H.J. CHANG2, M.J. KIM2, S.C. PARK2, J.H. OH2
1National Cancer Center, Proton Therapy Center,
Goyang-si-, Korea Republic of
2National Cancer Center, Center for Colorectal Cancer,
Goyang-si-, Korea Republic of
Purpose or Objective
To investigate clinical outcome of non-metastatic rectal
cancer patients with extremely high pretreatment serum
CEA level after radical surgery following preoperative
chemoradiotherapy
Material and Methods
A total of 959 patients with clinical stage II-III rectal
cancer who underwent preoperative chemoradiotherapy
followed by radical surgery between October 2001 and
July 2011 were retrospectively analyzed. There were 332
patients with elevated pretreatment serum CEA level (>
5ng/ml) and among them, we defined 23 patients with CEA
level of > 50 ng/ml as an extremely high pretreatment CEA
group. Overall survival rate, relapse-free survival rate,
locoregional recurrence-free survival rate and distant
metastasis-free survival rate were compared between
pretreatment CEA levels of 5-50 ng/ml and > 50 ng/ml.
Results
Median follow-up duration was 69 months (range, 3-165).
The five-year survival rate were 80.5% and 73.4%, and the
10-year survival rate were 64.5% and 73.4% in patients
with pretreatment serum CEA level of 5-50 ng/ml and > 50
ng/ml, respectively ( p = 0.672). The extremely high CEA
group (> 50 ng/ml) had significantly lower relapse-free
survival rate (RFS) at 5-year and 10-year than patients
with CEA level of 5-50 ng/ml (5-year RFS 70.6% versus.