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Conclusion
We reveal a critical pathway linking ATM and SPOP in
regulation of prostate cancer initiation and therapeutic
responses to radiation. This also provides the first
evidence for a pathophysiological relevant mutation
linked to ATM phosphorylation in the DDR.
Award Lecture: Jack Fowler University of Wisconsin
Award
OC-0375 Dosimetric quantification of the „true“ ano-
inguinal lymphatic drainage of anal cancer patients
H. Dapper
1
, G. Habl
1
, M. Mayinger
1
, M. Oechsner
1
, S.E.
Combs
1
, D. Habermehl
1
1
Klinikum rechts der Isar der Technischen Universität
München, Department of Radiation Oncology, München,
Germany
Purpose or Objective
The ano-inguinal lymphatic drainage (AILD) to the inguinal
lymph nodes is located in the subcutaneous adipose tissue
on the medial thigh. Even though those node-vessels are
very thin and hardly to detect with lymphangiography, this
fact is described and shown in standard anatomy atlases.
New fluorescence-imaging methods like the indocyanine-
green-method corroborate this fact. Anal cancer (AC)
patients undergo a combined chemoradiation (CRT)
protocol and the clinical target volume (CTV) encompasses
the inguinal lymphdrainage because of its affection in
about 30% of all patients. Current contouring atlases
suggest delineation of the primary tumor region, the
mesorectum, inguinal and iliacal lymph nodes but do not
advise the inclusion of the true AILD. Aim of this work was
the retrospective analysis of the incidental dose to the
AILD in an anal cancer patient cohort who underwent
definitive CRT with VMAT-IMRT and using structure sets
according to current guidelines.
Material and Methods
VMAT-IMRT plans of 10 anal cancer patients who had been
treated with CRT during 2014 and 2016 were analyzed. On
these plans we created a new volume, the expected ano-
inguinal lymph drain (AILD). Based on anatomic
descriptions, we connected the soft tissue between the
anus and the inguinal vessels with the following
demarcations: The caudal demarcation was defined 2 cm
below the tuberculum minus. The cranial end of AILD was
at the level of the symphysis (anal) or where no more soft
tissue connection between anus and inguinal could be
identified (inguinal). Ventral demarcation was the femoral
skin, dorsal was the transition of the gluteal muscles to
the subcutaneous adipose tissue. The lateral demarcation
was the adductor muscles (anal) and the medial femur
bone or at least 0.5 cm around femoral vessels (inguinal).
We examined dose parameters (minimum, maximum,
median, V10, V20, V30, V40, V45, V50) that were
delivered to the AILD target volume and the AILD outside
of the previous PTV (AILD-PTV) as represented in the dose-
volume histogram.
Results
All of the 10 patients received at least 39.6 Gy to the
inguinal lymph nodes, 45 Gy to the iliacal lymph nodes and
50.4 Gy to the primary tumor side. The median volume of
AILD and AILD-PTV was 1066 cm3 and 689 cm3,
respectively. Mean Dmin, Dmax and Dmean were 5.5 Gy,
58.1 Gy and 38.4 Gy for AILD and 5.5 Gy, 55.2 Gy and 31.1
Gy for AILD-PTV, respectively. Mean V30, V40, V45, V50
for AILD was 71%, 55%, 45% and 31%, respectively. For
AILD-PTV it was 57%, 29%, 18% and 5%, respectively.
Conclusion
At least 71% of the volume of the expected AILD received
at least an expected required treatment dose of 30 Gy
incidentally. Especially the caudal parts of the created
volumes, with a clear distance to the previous PTVs,
received an inadequate therapeutic dose. Concerning the
low number of locoregional relapses in AC patients after
definitive CRT one has to balance increased skin side
effects by including the AILD into the standard CTV against
a rigid oncological-anatomical interpretation of the local
lymphatic drainage.
Award Lecture: Company Award Lectures
OC-0376 Trajectory Optimization in Radiotherapy
Using Sectioning (TORUS)
C. Locke
1
, K. Bush
1
1
Stanford Cancer Center, Radiation Oncology, Stanford,
USA
Purpose or Objective
One of the most challenging problems in trajectory
optimization for radiotherapy is properly handling the
synchronization of the medical accelerator’s dynamic
delivery. The initial coarse sampling of control points
implemented in a Progressive Resolution Optimization
type approach (VMAT) routinely results in MLC aperture
forming contention issues as the sampling resolution
increases. IMRT based solutions such as 4Pi avoid MLC
synchronization issues through use of a static gantry, but
inevitably suffer from longer treatment times. This work
presents an appoach to optimize continuous, beam-on
radiation trajectories thorough exploration of the
anatomical topology present in the patient and formation
of a novel dual metric graph optimization problem.
Material and Methods
This work presents a novel perspective on trajectory
optimization in radiotherapy using the concept of
sectioning (TORUS). TORUS avoids degradation of 3D dose
optimization quality by mapping the connectedness of
target regions from the BEV perspective throughout the
space of deliverable coordinates. This connectedness
information is then incorporated into a graph optimization
problem to define ideal trajectories. The unique usage of
two distance functions in this graph optimization permits
the TORUS algorithm to generate efficient dynamic
trajectories for delivery while maximing the angular flux
through all PTV voxels. 3D dose optimization is performed
for trajectories using the Varian’s Photon Optimizer
(version 13.6.23).
Results
The TORUS algorithm is applied to three example
treatments: chest-wall, scalp, and the TG-119 C-shape
phantom. When restricted to only coplanar trajectories
for the chest-wall (dose distributions shown in Figure 1)
and scalp cases, the TORUS trajectories are found to
outperform both 7 field IMRT and 2 arc VMAT plans in
delivery time, organ at risk sparing, conformality, and
homogeneity. When the coplanar restriction is removed
for the TG-119 phantom and the static non-coplanar
trajectories are optimized, TORUS trajectories have
superior sparing of the central core avoidance with shorter
delivery times, with similar conformality and