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ESTRO 36 2017
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The latest data from large prospective phase III hypo-
fractionation studies, such as the CHHiP trail, support the
notion that the α/β ratio for prostate cancer might be as
low as 1.5Gy, and therefore offer the opportunity to
utilise hypo-fractionation to broaden the therapeutic
ratio. Additionally, highly conformal treatment plans and
reduced margins due to advanced image guidance as well
as the use of adaptive approaches further decrease the
doses administered to the organs at risk. The broadened
therapeutic ratio and the highly conformal planned and
accurately administered treatment plans allow for further
dose escalation to the prostate while maintaining low
toxicity. However, with the rectum and the bladder being
- more or less - directly adjacent to the prostate there is
still a need for an approach to further reduce the dose
delivered to the organs at risk.
Reviewing the current literature reveals that spacers offer
an invasive, but safe and effective way to partly overcome
the spatial proximity by introducing additional material
between the prostate and the rectum. The increased
distance – which is mostly reported to be in the range of
approximately 1 cm – is clearly correlated to a significant
reduction of administered doses and the volumes of the
rectum receiving high doses respectively; including the
anterior rectal wall which can otherwise hardly be spared.
Especially the clinically important volumes receiving a
high percentage of the prescribed dose or an EQD
2
of more
than 60 or 70 Gy, which could lead to severe acute and
late side effects can be significantly reduced. Several
studies clearly demonstrate these dosimetric benefits of
the different materials currently available. Nevertheless,
there is a certain learning curve that has to be absolved
to fully exploit the potential of such spacers. Another
property that all of them share is that the materials are
resorbed after a certain time. While all the different
materials/approaches such as hyaluronic acid, hydrogels
or balloons are fundamentally based on the same principle
– to create a space between the prostate and the anterior
rectum wall – each has slightly different characteristic.
The spacer balloon (Bioprotect
TM
) for example, has been
shown to result in an advantageous dose distribution
compared to spacer gels; however, it also has been shown
to shrink substantially during the course of a treatment,
thus losing some of its initial advantage.
Factors such as the detailed course of the resorption,
together with the handling during injection/placement,
the achievable increase of the distance, the actual shape
and its stability, the possible influence on prostate
movements, as well as the possible toxicity/side effects
inflicted by the spacer itself are the factors that need to
be considered when comparing the different
materials/approaches.
According to the available literature, there is no evidence
yet that one material is generally superior to the others,
showing only slightly different properties that need to be
weighted to choose the one fitting the respective
requirements. However, several of the properties still
need to be further evaluated and compared offering
interesting research opportunities.
SP-0494 Using a MRI-guided radiation therapy system
for prostate cancer patients
O. Bohoudi
1
, A. Bruynzeel
1
, S. Senan
1
, B. Slotman
1
, M.A.
Palacios
1
, F. Lagerwaard
1
1
VUMC, Radiotherapy, Amsterdam, The Netherlands
Recently, stereotactic MR-guided adaptive radiation
therapy (SMART) for prostate cancer has been clinically
implemented at our center, using the MRIdian system
(Viewray, Inc, Cleveland OH). This dedicated device
combines a split-bore 0.35T MRI which has real-time
imaging possibilities, and a radiotherapy delivery system
consisting of a ring gantry with three multileaf collimator-
equipped 60Co heads. An integrated Monte Carlo-based
treatment planning system in combination with an
independent adaptive QA system, allows for online
adaptive (re-)planning based on the actual daily anatomy
for optimal dose delivery. We report on the first year of
clinical experience with SMART for prostate patients. Here
we describe the clinical implementation and workflow,
provide details on daily plan adaptation and gated
radiation delivery under real-time MRI-guidance.
Symposium: Young ESTRO meets ESTRO School
SP-0495 Introduction of FALCON (Fellowship in
Anatomic delineation and CONtouring) online
contouring system as a tool for e-learning
J.G. Eriksen
1
1
Odense University Hospital, Department of Oncology,
Odense, Denmark
Heterogeneity in contouring of target volumes and organs
at risk is one of the major uncertainties for modern
radiotherapy planning. Competencies in delineation
requires both knowledge and skills obtained under
supervised practice in the clinic. Several online
possibilities for training contouring exists and can be a
valid supplement in training and maintaining of skills in
delineation. The ESTRO teaching programs called FALCON
(Fellowship in Anatomic delineation and CONtouring) –
using the EduCase platform - is presented.
SP-0496 Role of radiotherapy in the treatment of
stage IIIA/pN2 non-small cell lung cancer
L. Käsmann
1
1
University of Lübeck, Department of Radiation
Oncology, Lubeck, Germany
Lung cancer is the leading cause of cancer mortality,
surgery and radiotherapy play key roles in curative
treatment of this disease. Stage III comprises a
heterogeneous group of tumours and an optimal
multimodal treatment is warranted. However, the role of
postoperative radiotherapy in the treatment of stage
IIIA/pN2 non-small cell lung cancer (NSCLC) remains
controversial. Pre-operative staging based on endoscopy
and the use of FDG-PET has improved in the last decade.
Radiotherapy technology is also emerging with 4D-CT
simulation and cone beam CT for image-guidance resulting
in improved survival. Meta-analysis of the PORT phase III
studies using several radiotherapy technique (Cobalt, 2D-
planned, 3D-conformal) show conflicting data. In the first
part of this presentation we will outline the controversy
of radiotherapy in the treatment of stage IIIA/pN2 non-
small cell lung cancer according to the latest literature
and international guidelines. Besides we will present an
interesting case with focus on treatment planning, target
definition as well as delineation guidelines using the e-
learning programmes "Falcon" and "Dove" for a practical
overview.
SP-0497 Role of radiotherapy in the treatment of
stage IIIA/pN2 non-small cell lung cancer
B. Jeremic
1
1
Belgrade, Serbia,
Stage III non-small cell lung cancer (NSCLC) is a
heterogeneous disease presentation based on the range of
patient and tumor characteristics. Concurrent radio-
chemotherapy (RT-CHT) is the standard treatment
approach for inoperable stage III NSCLC. However, in
certain favorable subsets of patients with Stage III, namely
those with low burden stage disease (i.e. IIIA/pN2), there
seems to be greater potential for cure. In this setting,
treatment regimens consisting of surgery alone or in
combination with adjuvant CHT- and/or RT have been
historically among the most common approaches used,