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S726
ESTRO 36
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Purpose or Objective
Salvage radiotherapy (SRT) is the only potentially curative
therapy available for patients experiencing biochemical
recurrence after radical prostatectomy (RP), and likely
more effective when offered early at low PSA levels. This
work aims to retrospectively assess clinical outcome and
toxicity of patients treated with delayed SRT to
radiologically and/or histologically proven macroscopic
local recurrence.
Material and Methods
We report on a cohort of 56 patients with radiologically
detected isolated macroscopic local recurrence on MRI
and/or CT scan and treated with SRT between 2001 and
2015. Histological confirmation was available in 35 (63%)
patients. A dose of 64-66 Gy (2 Gy/fr) was delivered to the
prostatic bed followed by a dose escalation to 72-74 Gy (2
Gy/fr) to the site of macroscopic disease using image-
guided IMRT (IG-IMRT). Patients were treated with
concomitant short-course (6 months) of androgen
deprivation therapy. Biochemical relapse-free survival
(PSA nadir + 0.2 ng/ml; bRFS) and clinical relapse-free-
survival (cRFS) were calculated using Kaplan-Meier
method. Baseline, acute and late urinary and
gastrointestinal (GI) toxicity rates were reported using
CTCAE v4.
Results
Median age at SRT was 71 years (57-81). Out of 56
patients, 9 (16%) had pT3b disease and 19 (34%) had
positive surgical margins. Sixteen patients (29%) had
Gleason score ≥ 8 at RP. The median time from RP to SRT
was 58 months (5-172). Median pre-RT PSA was 2.8 ng/ml
(0.2-29). At a median follow-up of 39 months (8-153) post-
SRT, 20 patients (36%) had biochemical failure and 8 (14%)
developed distant metastasis. Median time to BF after SRT
was 30 months (13-116). The 3- and 5-year bRFS were
70.5% and 53,5%, respectively. The 3- and 5-year cRFS was
89.2% and 80%, respectively. High-risk patients (pT3b
and/or Gleason score ≥ 8) had 3- and 5-year bRFS of 54%
and 27%, while 3- and 5-year cRFS was 66.7% and 44.4%,
respectively. Univariate and multivariate analyses showed
that Gleason score ≥ 8 and perineural invasion were
associated with lower bRFS (p=0.005 and 0.046,
respectively). High-risk patients presented lower bRFS and
cRFS when compared to lower risk patients (p= 0.03 and
0.001, respectively). At baseline, 4 patients (7%) had
grade 3 urinary toxicity. Twelve patients (21%) developed
grade ≥ 2 acute urinary toxicities. Three patients (5%) had
grade 2 acute GI toxicities. No grade ≥ 3 acute GI toxicity
occurred. Nine patients (16%) had grade ≥ 2 late urinary
toxicities. No grade ≥ 2 late GI toxicity was reported.
Conclusion
Delayed SRT using dose escalated IG-IMRT to isolated
macroscopic local recurrence is associated with poor
oncological outcomes particularly in high risk patients
(i.e. pT3b and/or Gleason score ≥ 8). Toxicity profile
seems to be acceptable at a medium term follow up.
Patients with high risk features should be strongly
considered for earlier and intensified treatment
approaches.
EP-1355 Comparing toxicity in IMRT and particle
therapy of prostate cancer in a ROCOCO in silico trial
Y. Van Wijk
1
, E. Roelofs
2
, B. Vanneste
2
, S. Walsh
2
, P.
Lambin
2
1
Maastricht university, School for Oncology and
Developmental Biology, Maastricht, The Netherlands
2
MAASTRO clinic, Radio Oncology, Maastricht, The
Netherlands
Purpose or Objective
Studies have shown that dose escalation has positive
effect on tumour control probability when treating high
risk prostate cancer. However, due to the higher dose in
the rectum, the normal tissue complication probability
(NTCP) for gastral intestinal (GI) toxicity is increased. The
goal of this study is to investigate whether radiotherapy of
high-risk prostate cancer with light-ion particles results in
reduced NTCP when compared to IMRT. A comparison
between doses and NTCP was made for three modalities:
IMRT, proton therapy (IMPT) and carbon-ion therapy (IMIT)
(figure
1).
Material and Methods
Twenty-five consecutive patients with T3-T4 prostatic
cancer were included for high-dose radiotherapy. Proton
and Carbon-ion treatment planning was performed by the
ROCOCO trial partners following a strict clinical protocol,
prescribing 78 Gy (biologically equivalent dose) to the
target and compared pair-wise to generated IMRT
treatment plans. All 75 plans were analysed centrally to
compare the dose in the rectum (the main organ at risk)
and the NTCP for late rectal bleeding.
A validated multi-factorial NTCP model used the mean
dose (Gy) in the rectum and the percentage of the rectum
receiving more than 75 Gy (V75) as dosimetric predictors.
It also included a set of clinical predictors such as
haemorrhoids and hormonal therapy.
Results
An overview of the results is shown in table 1.
The mean dose in the rectum resulting from the IMRT,
proton and carbon-ion plans was 42.9 Gy [range: 30.8-47.2
Gy], 30.8 Gy [range: 23-45.2 Gy] and 18.9 Gy [range: 11.8-
33.3 Gy] respectively. The V75 for the IMRT, proton and
carbon-ion was 3.2% [range: 0.3-10.8 %], 2.1% [range: 0.5-
4.3 %] and 1.9% [range: 0.6-3.9 %] respectively. Both
proton and carbon-ion plans showed improvement with
respect to the IMRT plans in both dosimetric parameters,
and for carbon-ions it showed an improvement when
compared to protons.