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dose levels (24 Gy, 30 Gy and 36 Gy all in 3 fractions) using
a time-to-event continuous reassessment method design.
Pazopanib was continued post-radiotherapy as
maintenance therapy until disease progression.
Results
Thirteen patients were enrolled, with a median follow-up
of 19 months. Their median age was 66 years, with 54%
male and 46% female patients. No dose-limiting toxicities
were noted at dose levels 1 or 2. Of 7 patients at dose
level 3, 1 patient experienced a dose-limiting toxicity
consisting of grade 4 hypoglycemia. Grade 3 to 4
pazopanib-related adverse events (AEs) occurred in 38% of
patients (8%, 0%, 32% for respectively dose level 1, 2 and
3).
Table:
Treatment-related
adverse
events
Local control was achieved in all irradiated lesions, we
noted a complete local response in 1 irradiated lesion
(8%), partial response in 6 irradiated lesions (46%), and
stable disease in 6 irradiated lesions (46%) as best
response. Mean duration of local control was 23 months
(95% confidence interval 16 - 31). Assessment of responses
outside the radiation field revealed that 5 of 13 patients
(38 %) developed a partial response, 7 patients (54 %) had
stable disease and 1 patient (8%) had progressive disease
as best response. Median progression-free survival (PFS)
was 6.7 months (95% confidence interval 3 - 10).
Figure: Local control of irradiated lesions and distant
response of non-irradiated lesions: best response
Conclusion
SBRT in combination with pazopanib treatment is well-
tolerated with long-term local control and favourable
response rates outside the radiation field. Larger trials are
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. Zamboglou
1
, V. Drendel
2
, C.A. Jilg
3
, H.C. Rischke
1
, B.
Teresa I.
4
, T. Krauss
5
, M. Werner
2
, M. Bock
6
, M. Langer
5
,
P.T. Meyer
4
, A.L. Grosu
1
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
68
Ga-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
68
Ga-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.