ESTRO 36 Abstract Book

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S723 ESTRO 36 2017
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The results demonstrate that bladder filling helps limit
dose to the small bowel, and therefore is of paramount
importance that every effort is made to ensure
consistency of bladder filling for patients who are
undergoing pelvic IMRT.
EP-1363 Clinical efficacy of a dose escalated and
hypofractionated pelvic IMRT study in prostate cancer
A. Khan1,2, K. Thomas3, L. Truelove4, M. Ferreira1,2, S.
Gulliford5, H. McNair6, C. Parker2, R. Huddart1,2, D.
Dearnaley1,2
1 Institute of Cancer Research, Division of Radiotherapy
and Imaging, Sutton, United Kingdom
2 Royal Marsden NHS Trust, Academic Urology Unit,
Sutton, United Kingdom
3 Royal Marsden NHS Trust, Research Data management
and statistics unit, London- United Kingdom, United
Kingdom
4 Institute of cancer research and Royal Marsden NHS
Trust, Bob Champion Unit, Sutton, United Kingdom
5 Institute of cancer research and Royal Marsden Hospital,
Joint Department of Physics, London, United Kingdom
6 Institute of cancer research and Royal Marsden NHS
trust, Department of physics, London, United Kingdom
Purpose or Objective
The role of pelvic lymph node (PLN) radiotherapy in high-
risk localised prostate cancer remains controversial. The
dose to PLN is limited by bowel toxicity and the use of
intensity modulated radiotherapy (IMRT) has been
developed to improve the therapeutic ratio. The IMRT
trial was a phase I/II trial conducted in 426 patients at a
single centre, with the aim of exploring dose- escalated
and hypofractionated regimes of pelvic irradiation. We
report the long term outcomes of this trial cohort.
Material and Methods
Eligible patients had high risk (>T3a, Gleason ≥8 or PSA
≥20) disease with an estimated risk of lymph node
involvement of ≥30%, or lymph node positive
disease. IMRT was inverse planned to give 70-74Gy in 35-
37 fractions to the prostate and sequential patient cohorts
received 50Gy (n=25), 55Gy (n=70) and 60Gy (n=138) to
the pelvis in 35-37 fractions using a simultaneous
integrated boost technique. Positive lymph nodes received
an additional 5Gy boost. The remaining patients received
60Gy in 20 fractions to the prostate and 47Gy in 20
fractions over 4 weeks (n=64) or 47Gy in 20 fractions over
5 weeks (n=129) with an additional 4Gy boost to positive
lymph nodes. All patients received long course androgen
deprivation therapy, commencing at least 6 months before
radiotherapy. Biochemical failure was defined according
to the Phoenix criteria of the nadir +2ng/ml. Local
recurrence was confirmed with MRI and/or histological
confirmation. Distant staging with CT, MRI, nuclear
medicine bone scan or choline-PET CT was performed in
patients with biochemical relapse to establish all sites of
relapse.
Results
426 patients were recruited between 09/08/2000 and
09/06/2010 and the median follow up for the whole cohort
at the time of analysis was 7.6 years. Median age was 65
years (IQR 60-70 years) and median presenting PSA was
21.4 ng/ml (IQR10.2-42.8 ng/ml). The total number of
failure events was 169. Freedom from biochemical
/clinical failure at 5 years was 71% (95% CI 66%-75%). The
5 year prostate cancer specific survival was 92% (95% CI
89%-94%) and overall survival was 87% (95% CI 84%-90%).
Table 1 demonstrates the distribution of all documented
sites of relapse in each cohort.
Conclusion
Pelvic IMRT with dose escalation and hypofractionation is
associated with a low rate of pelvic recurrence. Freedom
from biochemical/clinical failure , cancer specific survival
and overall survival appear favourable, but high dose
pelvic IMRT requires testing in a phase 3 trial.
EP-1364 Substratification of prostate cancer risk
groups by core involvement and T stage may alter
prognosis
A.B. Hopper1, J.P. Einck1
1University of California San Diego, Radiation Medicine
and Applied Sciences, San Diego, USA
Purpose or Objective
Stratification of prostate cancer patients into low,
intermediate and high risk groups has shown to be an
important tool for prognostic outlook and treatment
planning. The intermediate and high risk groups have been
shown to be quite heterogenous though, and
substratification of these two groups may offer improved
guidance. Recent research has shown that a five group risk
stratification system may outperform the traditional three
group system in predicting prostate cancer specific
mortality, though this study did not use detailed staging
information or % core involvement (Gnanapragasam et al.
PLoS Medicine 2016). We sought to evaluate a five tiered
system, specifically substratification of intermediate (IR)
and high risk (HR) patients, using more detailed
information with regard to stage and biopsy core
involvement.
Material and Methods
378 intact PCa patients classified as IR or HR were treated
with radiotherapy at our institution between Jan 2005 and
Dec 2013, excluding any patients with prior metastases or
positive nodes on imaging. 48 patients were designated
as favorable (fIR) within the IR category with only one IR
factor, no predominant Gleason 4 pattern and % of cores
involved ≤ 50%. 147 patients were unfavorable IR (uIR)
with any Gleason pattern 4+3, >50% of cores involved or
multiple IR factors. 78 patients were favorable HR (fHR)
with only one of Gleason 4+4, PSA > 20, or clinical stage
T3. 105 patients were unfavorable HR (uHR) with a
combination of multiple HR factors or any Gleason 5
pattern (GS 9 or 10). Recurrence was defined using the
Phoenix criteria of PSA nadir + 2 ng/mL. Kaplan-Meier
analysis was used to compare biochemical progression free
survival (bPFS) between substratification groups. Median
follow up was 47 months.
Results
Log-rank testing showed no significant difference in total
bPFS between fIR and uIR groups (p=0.293). fHR and uHR
groups were found to have significantly different bPFS
(Figure 1, p=0.036). Overall comparison between the 4
groups showed a significant effect on bPFS (p = 0.038).
Pairwise analysis showed that there was not a significant