ESTRO 36 Abstract Book

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S380 ESTRO 36 2017
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73.8 Gy (all with 3DCRT), while 86 received WPRT at a
median dose of 50.4 Gy (45% by standard 3D box and 55%
by static field IMRT), plus a consequential 3D-CRT boost to
PB up to 75.6 Gy. The indication of both WPRT and of
adjuvant androgen deprivation (AAD), prescribed to 158
pts for a median of 14 months, was at the discretion of
each treating physician
Results
Median overall FU was 111 months. Owing to the gradual
introduction of WPRT over time, the cohort receiving
WPRT had a significantly shorter follow-up (90 vs 124
months, p<0.0001) and received significantly higher RT
dose (median 75.6 vs 73.8 Gy). All the remaining
prognostic variables were evenly distributed. At
univariable analysis SRT dose ≥75.6 Gy was the only
variable predictive of significantly increased 7-year bRFS
in the overall population and in the two subsets of pts with
PSA at SRT (PSA@SRT) ≤0.50 or >0.50 ng/mL. WPRT led to
a significant improvement in 7-year bRFS in the overall
population (84 vs 72%, p=0.02) and in the 144 pts with a
PSA at SRT >0.50 ng/mL (83% vs 64%, p=0.01). At
multivariable analysis (MVA) SRT dose ≤73.8 Gy,
pathologic stage ≥T3a, GS ≥7 and higher PSA@SRT, but not
WPRT, emerged as covariates independently predictive of
reduced post-SRT bRFS in the overall population. The
independent benefit deriving from higher SRT doses and
WPRT was confirmed in the 2 subsets of pts with PSA@SRT
≤ and >0.50 ng/mL, respectively. No benefit whatsoever
emerged from AAD (Fig 1).
In order to identify the subset benefiting most from WPRT
(Fig. 2) and dose-escalation, their roles were investigated
in the subset of 184 pts with at least 1 risk factor among
those individuated at MVA (GS ≥7, pT≥3a, and PSA at SRT
>0.50 ng/mL). In this subset MVA confirmed the
independent role of WPRT (HR 0.47, p=0.04) and SRT doses
≥75.6 Gy (HR 0.46, p=0.03).
Neither WPRT nor higher SRT doses led to any significant
increase of either acute or late toxicities.
Conclusion
Despite its retrospective nature, this study lends support
to the use of both WPRT and SRT doses ≥75.6 Gy in the
salvage setting in node-negative patients with ≥1 risk
factor among PSA at SRT >0.50 ng/mL, Gleason score ≥7
and pathologic stage ≥T3a.
PO-0731 Comparison of two fractionation schemes in
prostate cancer patients treated with robotic SBRT
F. Akyol1, P. Hurmuz1, G. Ozyigit 1
1Hacettepe University- Faculty of Medicine, Department
of Radiation Oncology, Ankara, Turkey
Purpose or Objective
The aim of this study is to evaluate the long term
treatment results of two different fractionation schemes
and PSA bounce phenomenon in our patients treated with
robotic stereotactic body radiotherapy (rSBRT) for
prostate cancer.
Material and Methods
We evaluated the medical records of 106 patients who
were treated between June 2007 and June 2015 for
prostate cancer in our department with CyberKnife™.
D’Amico risk classification system (1998) was used to
group patients. In the low risk (LR) group (n=54) 20
patients received androgen blockade (AB) (for volume
reduction or else purposes). In the intermediate risk (IR)
group (n=52) 42 patients received neoadjuvant/adjuvant
AB. According to our institution’s treatment protocol
rSBRT was delivered in 5 fractions to a total dose of 36.5
Gy either sequentially (n=58) or every other day (n=48).
‘Cavanagh definition’ (≥0.2 ng/mL) was used to define
‘PSA bounce phenomenon’.
Results
Median follow up time was 56 months. Only one patient
died due to pulmonary thromboembolism. Two patients in
the LR group and 3 patients in the IR group had PSA
relapses. In the whole group 5 year biochemical relapse
free survival (BRFS) rate was 93.4% (LR; 97.1% vs. IR;
89.2%; p=0.6). Five year BFRS rate in patients treated with
sequential scheme was 92% compared to 100% for every
other day scheme (p=0.3). PSA bounce phenomenon was
observed in 17 patients (16%) and among them only one
patient had PSA relapse. Five year BRFS rate was 89% in
patients with PSA bounce phenomenon compared to 94.2%
in patients without bounce (p=0.9). There was no
difference in the incidence of PSA bounce for different
treatment schemes. All of the patients received the
planned rSBRT dose without any breaks in the treatment
schedule due to toxicity. Late grade III gastrointestinal
system toxicity was observed in 4 patients (3 sequential,
1 every other day scheme; p=0.6). No patients reported
late grade III genitourinary toxicity.
Conclusion
Our rSBRT treatment protocol was very well tolerated with
high rates of 5 year BRFS rates. PSA bounce phenomenon
may also be observed after rSBRT for prostate cancer. We
did not find a relation between PSA bounce and
biochemical relapse. The fractionation scheme of the
rSBRT in our protocol did not affect the treatment results
and toxicity.
PO-0732 Toxicity and outcome in moderately
hypofractionated radiotherapy for 590 prostate cancer
patients
A. Maucieri1, B.A. Jereczek-Fossa2, D. Ciardo1, C. Fodor 1,
P. Maisonneuve3, A. Surgo1, S. Volpe 2, G. Marvaso1, A.
Vavassori1, A. Viola2, G. Musi4, O. De Cobelli5, R.
Orecchia6
1European Institute of Oncology, Department of
Radiation Oncology, Milan, Italy
2European Institute of Oncology - University of Milan,
Department of Radiation Oncology, Milan, Italy
3European Institute of Oncology, Division of
Epidemiology and Biostatistics, Milan, Italy
4European Institute of Oncology, Department of Urologic