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salvage HDRB was based on the Phoenix definition. All
non-failure patients were followed for a minimum of 5
years. Eighteen different clinical risk features were
collected from each patient. Machine Learning was used
to identify subpopulations that would most likely to
remain biochemically disease free after the
treatment. Decision tree algorithms were constructed
using Matlab R 2011a. The complexity of the decision tree
was fine-tuned by selecting the optimum number of
observations per terminal node that minimized
the “Leave One Out Cross-Validation” estimation of the
deviance. Results were compared to those obtained using
Ensemble Methods. Random permutation experiments
were also performed to estimate the probability that the
tree found was the result of random variations.
Results
A subpopulation of patients with a high risk of biochemical
failure after salvage HDRB was identified. Those patients
with a fraction of positive nodes from those sample that
was greater than 0.354 and disease free interval less than
4.12 years had a failure rate after salvage HDRB of 0.75 vs
0.38 for the remainder of the population,
Figure 1
. The
probability that the conclusions reached in this paper are
not due to random fluctuations is 0.7,
Figure 2
.
Figure1.
The Optimal Decision Tree obtained for
predicting failure after Salvage HDRB.
Figure 2.
Random permutation of output labels. 1000
iterations were created in each case were the outcome of
was randomly permuted. Not correlation between
features and outcome should be present in this case. The
probability of obtaining a cross-validated leave one out
error smaller than the one obtained by the tree in Figure
1 was calculated.
Conclusion
Patients with a fraction of positive nodes higher than 0.35
and a disease free interval bigger than 4.12 years are at
higher risk of biochemical failure after salvage HDBR.
Machine Learning is effective in identify subtle variables
that can affect the treatment outcome.
Proffered Papers: Breast
OC-0177 Brachytherapy for the Palliation of Dysphagia
Owing to Esophageal Cancer: A Systematic Review.
L. Fuccio
1
, D. Mandolesi
1
, A. Farioli
1
, C. Hassan
2
, L.
Frazzoni
1
, A. Guido
3
, F. Violante
1
, C. Pierantoni
1
, A.
Galuppi
3
, F. Bazzoli
1
, A. Repici
4
, A. Morganti
3
1
S.Orsola-Malpighi University Hospital, Department of
Medical and Surgical Sciences, Bologna, Italy
2
Nuovo Regina Margherita Hospital, Gastroenterology
Unit, Rome, Italy
3
S.Orsola-Malpighi University Hospital, Radiation
Oncology Unit, Bologna, Italy
4
Humanitas Research University Hospital, Endoscopy
Unit, Rozzano MI, Italy
Purpose or Objective
The management of dysphagia owing to eso phageal
cancer is challenging. Brachytherapy has been proposed as
an alternative option to stent placement. We performed a
systematic review to examine its efficacy and safety in the
resolution of dysphagia.
Material and Methods
Prospective studies recruiting at least 20 patients with
malignant dysphagia and published up to April 2016 were
eligible. The dysphagia-free survival (DFS) and adverse
event rates were pooled by means of a random effect
model.
Results
Six studies for a total of 9 treatment arms (623 patients)
were eligible for inclusion. After 1 month since treatment,
the DFS rate was 86.9% [95%CI: 76.0%–93.3%]; after 3
months, it was 67.2% [95%CI: 56.1%–76.7%]; after 6
months, it was 47.4% [95%CI: 38.5%–56.5%]; after 9
months, it was 37.6% [95%CI:30.0%–45.9%]; and, finally,
after 12 months, it was 29.4% [95%CI: 21.6%–38.7%]. The
heterogeneity between studies was high at 1-, 3- and 6-
month assessment; the values of I
2
were 86.3%, 80.0% and
57.8%, respectively. The meta-regression analysis showed
total radiation dose and number of fractions as the only
positively influencing factors. Severe adverse event rate
was 22.6% (95%CI 19.4–26.3). The main reported adverse
events were brachytherapy-related stenosis (12.2%) and
fistula development (8.3%). Two cases (0.3%) of deaths
were reported due to esophageal perforation.
Conclusion
Brachytherapy is a highly effective and relatively safe
treatment option therefore its underuse is no longer
justified. Further studies should investigate the optimal
radiation dose and number of fractions able to achieve the
highest DFS rates.
OC-0178 Demonstration of Catheter Insertion Using
Electromagnetic Guidance in Breast Brachytherapy
H. Brastianos
1
, T. Vaughan
2
, A. Lasso
2
, M. Westerland
1
, J.
Gooding
1
, T. Ungi
2
, G. Fichtinger
2
, C. Falkson
1
1
Queen's University Cancer Research Institute, Radiation
Oncology, Kingston- Ontario, Canada
2
Queen's University, School of Computing, Kingston-
Ontario, Canada
Purpose or Objective
Accelerated partial breast irradiation using multi-catheter
interstitial brachytherapy may be used for early stage
breast cancers. To ensure ideal dosimetry over the tumor
bed, the catheters need to be placed in parallel with equal
spacing. The breast is a deformable organ; thus, placing
catheters in the correct position is challenging. To ensure
adequate spacing and position, we will apply real-time
electromagnetic guidance (EM) in combination with
ultrasound (US) to optimize the catheter insertions. This
study will discuss the use of electromagnetic tracking
catheter with ultrasound to insert catheters in phantoms.