181 / 1096
S168
ESTRO 36
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Figure: Contouring with the aid of MRI and CT. Red: GTV.
Green: pancreatic head. Blue: duodenum.
Conclusion
MRI-guided SBRT for pancreatic cancer with individually
evaluated margins is technical feasible and safe, with no
treatment related grade ≥3 toxicity. New strategies are
applied, including an individual corset to reduce breathing
motion, MRI based contouring and simulation of motion-
integrated dose distributions.
PV-0322 Rapid Early Response of Gastroesophageal
Junction Tumors During Real-time MRI-Guided
Radiotherapy
H. Musunuru
1
, S. Rosenberg
1
, J. Bayouth
1
, K. Mitteur
1
, M.
Ritter
1
, B. Paliwal
1
, M. Witek
1
, A. Baschnagel
1
, N.
Uboha
2
, S. Lubner
2
, N. Loconte
2
, P. Harari
1
, M. Bassetti
1
1
University of Wisconsin Hospital and Clinics, Radiation
Oncology, madison, USA
2
University of Wisconsin Hospital and Clinics, Medical
Oncology, Madison, USA
Purpose or Objective
Multimodality comprehensive therapy has become the
standard of care for locally advanced esophageal and
gastroesophageal junction tumors. Tumor response to
chemoradiation correlates with outcomes, however full
response information generally awaits esophagectomy.
Intra treatment predictors of response may allow
improved personalization of therapy. Daily MRI allows
direct quantification of GEJ tumor size. The aim of this
study is to evaluate volumetric changes in gross tumor
volume (GTV) for gastroesophageal junction (GEJ) cancer
patients undergoing MRI-guided radiation therapy, as part
of neoadjuvant chemoradiotherapy
Material and Methods
Five GEJ adenocarcinoma patients underwent MRI during
simulation and with each treatment fraction immediately
prior to radiation delivery. The GTV primary was
contoured on MRI scans at fractions 5, 10, 15, 20 and 23
and compared to the baseline GTV (Fig 1). Change in GTV
across time was expressed as percentage difference
(between baseline and different fractions and between
individual fractions) and in terms of absolute volume(cc).
Results
Median age and follow-up period for this cohort were 68
years and 46.5 days. The treatment regimen consisted of
weekly carboplatin (AUC 2mg/ml/min) and paclitaxel
(50mg/m
2
) with concurrent radiotherapy, 50.4Gy in 28
fractions in three patients and 41.4Gy in 23 fractions in
the remaining two patients. The earliest decrease in GTV
(% change) was noted at fraction 10 when compared to
baseline (Mean -52%, SD 4.6%; Fig 2A). Evaluation of
percentage change in the GTV between different fractions
(i.e. fraction 5 and fraction 10 etc.) also showed that the
earliest change occurred between fractions 5-10 (Table 1).
Mean (SD) of GTV at baseline and at fractions 5, 10, 15, 20
and 23 were 94.7cc(15.4), 93.9cc(14.8), 46.3cc(7.8),
39.7cc(6), 33.2cc(4.7) and 33.2cc(4.7), respectively.