ESTRO 36 Abstract Book

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S141 ESTRO 36
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Purpose or Objective
Prostate cancer is the most frequent malignancy in
African-Caribbean men, a population sharing common
genetic traits with African-American (AA) but presenting
also genomic and epidemiologic specificities. Despite
socio-economic disparities with French mainland, all
patients were treated within the French state-financed
equal-access healthcare system. In this study, we report
biochemical outcomes of patients treated by
brachytherapy in our department from 2005 to 2014 in an
African-Caribbean population
Material and Methods
370 consecutive patients receiving I125 brachytherapy as
a curative treatment for early-stage (localized) disease
between 2005 and 2014 were recorded. Selected patients
presented with low risk disease: initial PSA (iPSA) < 10
ng/mL, clinical stage <= T2a, Gleason <7. Patients with
intermediate risk of recurrence were also included on a
case to case basis with PSA <15 or Gleason 7 (3+4).
Biochemical failure free-survival (BFFS) was defined
according to the ASTRO nadir+2 definition.
Results
The 3-year and 5-year BFFS for the entire cohort were
98.3% and 91.6% respectively. For patients with low and
intermediate-risk disease, the 5-year BBFS rates were 92.1
and 90.8%, respectively. In univariate and multivariate
analysis, only Gleason score ( ˂7 vs 7; P = 0.030 ˂0.05) was
a significant predictor of biochemical failure. The overall
rate of late and acute grade 2 or higher Genito-urinary
toxicity was 12.6% and 10.3 %.
Conclusion
In this large single-center series, brachytherapy achieved
excellent rates of medium-term biochemical control in
both low- and selected intermediate-risk localized
prostate cancer in African-caribean patients.
Brachytherapy seems to be an excellent choice of
treatment, with excellent outcomes and limited morbidity
for African-Caribbean populations. To our knowledge, our
series is the first presenting brachytherapy results in this
specific population.
OC-0274 Comparison of MRI/CT fusion and CT for
prostate post-implant dosimetry using sector analysis
N. Katayama 1, M. Takemoto2, A. Takamoto3, S.
Sugiyama1 , K. Hisazumi1, K. Watanabe1, H. Ihara1, K.
Katsui 1, Y. Nasu3, S. Kanazawa3
1 Okayama University Graduate School of Health Sciences,
Department of Radiology, Okayama, Japan
2 Himeji Red Cross Hospital, Department of Radiotherapy,
Himeji, Japan
3 Okayama University Graduate School of Health Sciences,
Department of Urology, Okayama, Japan
Purpose or Objective
Anatomical structures are well defined, so MRI/CT fusion
is considered the best method for postimplant dosimetry
of permanent prostate brachytherapy. We compared the
results obtained from MRI/CT fusion-based dosimetry with
those of CT-based dosimetry using sector analysis, and
analyzed the factors associated with the difference of the
whole prostate dose between the two dosimetry. This is
the first report which evaluated those factors using 3-
Tesla MRI in which contouring and fusion are thought to be
more accurate than in 1.5-Tesla MRI.
Material and Methods
The subjects were 81 consecutive patients treated with
144 Gy of brachytherapy alone using loose I-125
radioactive seeds. For postimplant analysis, CT and MRI
scans were obtained at 1 month after implantation. CT
and 3-Tesla T2-weighted MR images were fused and
aligned on the basis of seed distribution in MRI/CT fusion-
based dosimetry. Dosimetry was computed for the whole
prostate and for the prostate divided into anterior and
posterior sectors of the base, mid-gland, and apex (Fig.
1). The volumetric and dosimetric results were compared
between MRI/CT fusion-based and CT-based dosimetry
using a paired t test. Factors associated with the absolute
value of the difference of D90 between the two dosimetry
(|D90MRI/CT - D90CT|) were analyzed by multiple
regression. P values of <0.05 were defined to be
significant.
Results
D90 (176.7 Gy vs 173.0 Gy; p = 0.003) and V100 (97.2% vs
96.5%; p = 0.013) were significantly higher in MRI/CT
fusion-based dosimetry than in CT-based dosimetry.
Prostate volume (28.5 mL vs 30.8 mL; p < 0.001) was
significantly lower in MRI/CT fusion-based dosimetry than
CT-based dosimetry. Sector analysis showed a decrease in
MRI/CT fusion D90 at the anterior base (154.9 Gy vs 166.5
Gy; p < 0.001) and the posterior apex (169.7 Gy vs 177.6
Gy; p < 0.001), and increase in MRI/CT fusion D90 in the
anterior mid-gland (195.2 Gy vs 181.7 Gy; p < 0.001), the
posterior mid-gland (196.1 Gy vs 193.9 Gy; p = 0.030), and
the anterior apex (198.7 Gy vs 175.0 Gy; p < 0.001).
|D90MRI/CT - D90CT| was largest at the anterior apex
sector among 6 sectors (27.2 Gy). On multivariate
analysis, |D90MRI/CT - D90CT| of whole prostate are
associated with |prostate volume (PV)MRI/CT - PVCT| (p
= 0.036), |D90MRI/CT - D90CT| at the posterior base
sector (p = 0.035), |D90MRI/CT - D90CT| at the anterior
mid-gland sector (p = 0.011), and |D90MRI/CT - D90CT| at
the anterior apex sector (p = 0.004) (Table 1).
Conclusion
Several postimplant dosimetric variables were
significantly different on MRI/CT fusion vs CT. The
differences between the two methods of PV, D90 at the
posterior base, anterior mid-gland, and anterior apex
sectors may greatly influence the difference of D90 of the
whole prostate.
Proffered Papers: Physics treatment verification
OC-0275 Testing an MR-compatible afterloader for MR-
based source tracking in MRI guided HDR
brachytherapy
E. Beld1, P.R. Seevinck2, J. Schuurman3, F. Zijlstra2, M.A.
Viergever2, J.J.W. Lagendijk1, M.A. Moerland1
1UMC Utrecht, Department of Radiotherapy, Utrecht,
The Netherlands
2UMC Utrecht, Image Sciences Institute, Utrecht, The
Netherlands
3Elekta NL, Veenendaal, The Netherlands
Purpose or Objective