ESTRO 36 Abstract Book

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S291 ESTRO 36 2017
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needed to study the impact of the combination on overall
survival and PFS.
PV-0551 PSMA PET/CT vs MRI for GTV delineation in
prostate cancer: a comparison with histology
C. Zamboglou1, V. Drendel2, C.A. Jilg 3, H.C. Rischke1, B.
Teresa I.4, T. Krauss5, M. Werner 2, M. Bock6, M. Langer5,
P.T. Meyer4, A.L. Grosu1
1 Medical Center - University of Freiburg, Department of
Radiation Oncology, Freiburg, Germany
2 Medical Center - University of Freiburg, Department of
Pathology, Freiburg, Germany
3 Medical Center - University of Freiburg, Department of
Urology, Freiburg, Germany
4 Medical Center - University of Freiburg, Department of
Nuclear Medicine, Freiburg, Germany
5 Medical Center - University of Freiburg, Department of
Radiology, Freiburg, Germany
6 Medical Center - University of Freiburg, Department of
Radiology- Medical Physics Division, Freiburg, Germany
Purpose or Objective
The exact delineation of the intraprostatic tumour burden
is crucial for treatment planning in primary prostate
cancer (PCa). We compared 68Ga-HBED-CC-PSMA PET/CT
with multiparametric MRI (mpMRI) for gross tumour
delineation in patients with primary PCa based on slice by
slice correlation with histopathological reference
material.
Material and Methods
Patients with histopathologically proven primary PCa
underwent 68Ga-HBED-CC-PSMA PET/CT (n=10) and MRI
(n=7) followed by radical prostatectomy. Resected
prostates were scanned by ex-vivo CT using a special
localizer and prepared for histopathology in a customized
cutting device. Invasive PCa was delineated on a HE
stained histologic tissue slide and matched to ex-vivo CT
to obtain gross tumor volume (GTV-)histo. Ex-vivo CT
including GTV-histo and MRI data were matched to in-vivo
CT(PET). Consensus contours based on MRI (GTV-MRI),
PSMA PET (GTV-PET) or the combination of both (GTV-
union/-intersection) were delineated. In each in-vivo CT
slice the prostate was separated into 4 equal segments
(total 340 segements) and sensitivity and specificity for
PSMA PET and mpMRI were assessed by comparison with
histological reference material. Furthermore, the spatial
overlap with GTV-histo was measured. In the case of
multifocal PCa (4/7 patients), SUV values (PSMA PET) and
b-values (diffusion weighted MRI) were obtained for each
lesion.
Results
GTV-histo was detected in 225 of 340 segments (66%).
Sensitivity and specificity for GTV-PET, GTV-MRI, GTV-
union and GTV-intersection were 75% and 87%, 70% and
82%, 82% and 67%, 55% and 99%, respectively. GTV-histo
had on average the highest overlap with GTV-union
(57±22%), which was significantly higher than overlap with
GTV-MRI (p=0.016) and GTV-PET (p=0.016), respectively.
In every patient with multifocal PCa there was one lesion
which had both the highest SUV and the highest b-value
(mean and max), which was always the largest lesion in
histology.
Conclusion
68 Ga-HBED-CC-PSMA PET/CT and mpMRI showed high
sensitivity and specificity in detection of primary PCa. The
combination of both methods performed even better in
terms of sensitivity (GTV-union) and specificity (GTV-
intersection). A good spatial overlap with GTV-histo was
observed for PSMA PET/CT and mpMRI alone which was
significantly improved by GTV-union. Further studies are
warranted to analyse the impact of these preliminary
findings for therapeutic (focal therapy) strategies in
primary PCa.
PV-0552 Urethra-sparing SBRT for prostate cancer:
acute toxicity results from a randomized phase II trial
T. Zilli1, S. Jorcano2, S. Bral3, C. Rubio4, A. Bruynzeel5, A.
Oliveira 6, U. Abacioglu7, H. Minn 8, Z. Symon9, R.
Miralbell1,2
1Hôpitaux Universitaires de Genève, Radiation Oncology,
Geneva, Switzerland
2Teknon Oncologic Institute, Radiation Oncology,
Barcelona, Spain
3Onze-Lieve-Vrouwziekenhuis, Radiation Oncology, Aalst,
Belgium
4Hospital Universitario Sanchinarro, Radiation Oncology,
Madrid, Spain
5VU University Medical Center, Radiation-Oncology,
Amsterdam, The Netherlands
6Portuguese Institut of Oncology, Radiation Oncology,
Porto, Portugal
7Neolife Medical Center, Radiation Oncology, Istanbul,
Turkey
8University Hospital Turku, Radiation Oncology, Turku,
Finland
9Sheba Medical Center, Radiation Oncology, Ramat Gan,
Israel
Purpose or Objective
To present the acute toxicity results from a prospective
multicenter phase II randomized trial of short or
protracted urethra-sparing stereotactic body radiotherapy
(SBRT) for localized prostate cancer (PCa).
Material and Methods
From 08/2012 to 12/2015, 170 patients (pts) from nine
European centers with cT1c-3a N0 M0 PCa and a low risk
of nodal involvement (≤20%, according to Roach et al.)
were recruited and randomized according to two different
overall treatment time (OTT) schedules: either 9 days
(arm A, 84 pts), or 28 days, once-a-week, the same week-
day (arm B, 86 pts). The prescribed dose was 36.25 Gy in
5 fractions of 7.25 Gy to the prostate ± seminal vesicles in
both arms. The prostatic urethra, with a surrounding
margin of 3 mm, received a lesser dose of 5 x 6.5 Gy = 32.5
Gy. All patients were treated either with a VMAT or IMRT
technique under stereotactic conditions using Novalis
linacs and ExacTrac image-guided technology.
Genitourinary (GU) and gastrointestinal (GI) toxicity
(CTCAE v4.0 grading scale), IPSS, and QoL scores (EORTC
QLQ-PR25) were assessed at baseline, at the 5th fraction
(5fx), and 12th weeks (12W) since SBRT start.
Results
82 (median age 70 years) and 83 (median age 69 years)
pts, respectively, from arms A and B, were retained for
this analysis. Low-, intermediate-, and high-risk
presentation was respectively 22%, 63%, and 15% (arm A)
and 22%, 64%, and 14% (arm B). A 6-months androgen
deprivation was used in 44% and 45% of the pts in arm A
and B, respectively. The toxicity stopping rule of the study
during the first 3-months was never activated. In both
arms, Grade 1 GI toxicity increased from baseline to 5fx
(from 19.5% to 38% and from 23% to 32% for arms A and B,
respectively) returning back to baseline by W12 (18% for
Arm A and 25% for Arm B). Only 2 cases of grade 2 GI
toxicity (2.5%) were observed at 5fx in arm A. Grade 2 GU
toxicity rates at baseline, 5fx, and W12 were 2%, 17%, and
11% vs. 5%, 19% and 6% in arms A and B, respectively
(mainly moderate irritative and voiding symptoms). Only
one grade 3 GU toxicity was observed at W12 in arm B
(desobstructive TURP in a patient with a preexisting
history of acute urinary retention). Median IPSS scores at
the same endpoints were 6, 10, and 6 vs. 6, 10, and 7 for
arms A and B, respectively, with similar IPSS-based QoL
rates at baseline and W12 (80% of pts satisfied). No
changes in EORTC QLQ-PR25 scores for GU, GI, and sexual
domains were observed in both arms between baseline and
W12.