ESTRO 36 Abstract Book

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S61 ESTRO 36 2017
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Material and Methods
This is a multicentric Rare Cancer Network
) retrospective study launched in
February 2016. Demographic, therapeutic and outcome
data of 48 adult PS pts treated in 13 European and
American Institutions were collected in a common
database and then analysed. Median age was 64.5 years
(range: 22 - 87). Curative surgery was delivered in 35 pts
(prostatectomy = 19, cystoprostatectomy = 16), usually
with lymphadenectomy (n = 24). Curative radiotherapy
(RT) was delivered in 24 pts, as neoadjuvant (n = 2),
postoperative (n = 17), or as definitive treatment (n = 5).
Ten pts received neoadjuvant (n = 3) or adjuvant (n = 7)
chemotherapy. None of the patients received hormonal
therapy.
Results
Median follow-up was 67 months. Five-year local control
(LC), overall survival (OS), cancer-specific survival,
disease-free survival, and metastases-free survival rates
were 48.9%, 45.2%, 52.4%, 29.7%, and 31.2%, respectively.
Irradiated patients presented better 5-year LC (63.8% vs
38.8%, p = 0.2) but its impact was not confirmed in the 35
pts receiving curative surgery. In the subgroup of pT3-T4
patients treated with curative surgery, RT significantly
improved the 5-year LC (45.7% vs 0%, p = 0.007) and OS
(48% vs 0%, p = 0.014) rates. cT4 pts presented a
significantly lower 5-year OS (60.1% vs 29.5%, p = 0.001)
and LC (70.2% vs 11.4%, p < 0.001) rates. Histologic type
did not significantly influence the LC and OS, but pts
presenting a prostatic stromal sarcoma, a
rhabdomyosarcoma, or a sarcomatoid carcinoma showed a
trend toward a worse outcome (5-year LC [31.9% vs 59.2%]
and OS [28% vs 70%]).
Conclusion
Adult PS has a bad prognosis. More advanced diseases
present lower LC and OS rates. Curative RT should be
considered part of the multidisciplinary approach to PS.
Poster Viewing : Session 3: Treatment planning
PV-0131 MR-only prostate external radiotherapy
treatment planning - a multi-center/multi-vendor
validation
E. Persson 1, C. Gustafsson1,2, F. Nordström3, M. Sohlin3,
A. Gunnlaugsson4 , K. Petruson5, N. Rintelä6, K. Hed6, L.
Blomqvist7, B. Zackrisson7, T. Nyholm7,8, L.E. Olsson 2, C.
Siversson 9, J. Jonsson7
1 Skåne University Hospital, Hematology- Oncology and
Radiation Physics, Lund, Sweden
2 Lund University, Medical Physics, Malmö, Sweden
3 Sahlgrenska University Hospital, Medical Physics and
Biomedical Engineering, Gothenburg, Sweden
4 Skåne University Hospital, Oncology, Lund, Sweden
5 Sahlgrenska University Hospital, Oncology, Gothenburg,
Sweden
6 Karolinska University Hospital, Medical Radiation
Physics and Nuclear Medicine, Stockholm, Sweden
7 Umeå University, Radiation Sciences, Umeå, Sweden
8 Uppsala University, Immunology- Genetics and
Pathology, Uppsala, Sweden
9 Spectronic, Medical, Helsingborg, Sweden
Purpose or Objective
An important prerequisite for MRI only radiotherapy is the
generation of a synthetic CT (sCT) from MRI-data. This
study aims to validate the use of MriPlannerTM, a software
for MR to sCT conversion, for 170 prostate cancer patients.
Performed within the Swedish consortium Gentle
Radiotherapy, this multi-center study enables a large-
scale validation of calculated synthetic CTs for multiple
vendors. This is a presentation of the full results of the
MR-Only Prostate External RAdiotherapy (MR-OPERA)
study.
Material and Methods
The four participating centers had MriPlannerTM
(Spectronic Medical AB, Helsingborg, Sweden) installed as
a cloud based service. The software makes use of an atlas-
based generation method, called the statistical
decomposition algorithm, which generates sCTs from T2-
weighted MR-images. Study participation did not affect
treatment prescription, and the patients followed the
routine clinical workflow.
A T2-weighted MRI, covering the external body contour,
was added to the clinical MRI scan protocol. The MR-image
was sent from the MR-scanner workstation to the
MriPlannerTM platform. The generated sCT was
automatically returned to the treatment planning system.
A total of four different MR-scanners from two vendors and
two magnetic field strengths were included in the study.
For each patient, a CT-treatment plan was created and
approved according to clinical practice. The generated
sCT was rigidly registered to the CT, the structures
transferred, and the clinical treatment plan was
recalculated on the sCT. Separate external contours were
generated based on the sCT and CT images respectively.
The dose distributions from the CT-plan and the sCT-plan
were compared based on a set of DVH-parameters and
with gamma evaluation. Treatment techniques included
VMAT, IMRT and conventional treatment using two
commercially available treatment planning systems.
Results
The overall (multi-center/multi-vendor) mean difference
between sCT and CT dose distribution were 0.23%±0.42%
for PTV mean, 0.04%±0.27% for bladder mean and
0.16%±0.42% for rectum mean (1 s.d). Gamma evaluation
showed a mean pass rate of 99.12%±0.63% in the complete
body volume and 99.97%±0.13% in the PTV volume using a
2%/2mm global gamma criteria (1 s.d). The four centers
showed similar results. All evaluated DVH-criteria were
shown to be equivalent at a 95% confidence interval using
a two one-sided test of equivalence for paired samples.
Conclusion
The results of the MR-OPERA study showed that an MRI
only workflow using the MriPlanner was dosimetrically
accurate for a variety of vendors, field strengths and
treatment techniques. Minimal differences were observed
between sCT and CT dose distributions, and in comparison
to other uncertainties in radiotherapy, they can be
considered negligible. The proposed method will allow for
a straightforward implementation of an MRI only workflow
for external prostate radiotherapy at most clinics.
PV-0132 Comparison of planned versus simulated
delivered dose in IMRT for endometrial cancer
I. White1, D. McQuaid1, A. Dunlop1, N. Hopkins1, M.
Caputo1, S. Mason1, S. Lalondrelle1
1The Institute of Cancer Research and The Royal Marsden
NHS Foundation Trust, Radiotherapy, Sutton, United
Kingdom
Purpose or Objective
To quantify the planned versus the delivered radiation
dose using deformable image registration of cone beam CT
(CBCT), in patients treated with IMRT for endometrial
cancer.
Material and Methods
1. Post-hysterectomy patients treated with adjuvant IMRT
(4500cGy in 25 fractions) for endometrial cancer were
retrospectively dose tracked using CBCT on a commercial
treatment planning system (RayStation v5, Raysearch
Laboratories).
2. CBCTs were acquired days 1-4 and then weekly except
when error >5mm.
3. Rigid registration between the planning CT and each
CBCT was performed based on treatment position.
4. CBCT electron density values were established.