ESTRO 36 Abstract Book

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S93 ESTRO 36
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in 8 (6%) and unknown in 3 (2,5%) patients. Late skin
toxicity was registered in 29 (23,4%) patients, grade 1-2 in
28 (22,5%), grade 3 in 1 (0,8%). Late toxicity was
significantly related to the skin administered doses (≤ 55%
vs. > 55%, P < 0.05).
Conclusion
PBI delivered with 192Ir HDR-BRT in selected breast cancer
patients was associated to high local control and survival
with excellent cosmetic outcomes. An appropriate
patient selection and skin dose ≤ 55% provided optimal
clinical outcomes.
OC-0182 2nd breast conserving therapy with
interstitial BT vs mastectomy for treatment of local
recurrences
V. Smanykó1, N. Mészáros1, M. Ujhelyi2, G. Stelczer 1, T.
Major1, Z. Mátrai2, C. Polgár1
1 National Institute of Oncology, Center of Radiotherapy,
Budapest, Hungary
2 National Institute of Oncology, Center of Surgery,
Budapest, Hungary
Purpose or Objective
To compare the clinical outcomes of second breast
conserving therapy (BCT) with perioperative high-dose-
rate (HDR) interstitial brachytherapy (iBT) versus salvage
mastectomy (sMT) for the treatment of ipsilateral breast
tumor recurrences (IBTRs).
Material and Methods
Between 1999 and 2016, 92 patients who presented with
an IBTR after previous BCT were salvaged either with
reexcision and perioperative HDR multi-catheter iBT
(n=35) or sMT (n=57). In the BCT + HDR iBT group a median
of 7 (range: 4-23) catheters were implanted
intraoperatively. A total dose of 22 Gy in 5 fractions of 4.4
Gy was delivered to the tumor bed with a margin of 1-2
cm perioperatively on 3 consecutive days. Similar
proportion of patients received adjuvant chemotherapy in
the two groups (17% after BCT + HDR iBT vs 21% after sMT)
and/or hormonal treatments (71% vs 70%, respectively).
Five-year oncologic outcomes (including ultimate local
tumor control, regional tumor control, disease-free
survival [DFS], cancer specific survival [CSS], and overall
survival [OS]) were estimated by the Kaplan-Meier
method. Survival curves were compared with the log-rank
test.
Results
Mean follow up time was 63 months (range: 2-183) in the
BCT + HDR iBT group vs 30 months (range: 4-164) in the
sMT group. The mean diameter of IBTRs was 16.8 mm
(range: 2-70) vs 24.5 mm (range: 2-60), respectively.
There was no significant difference in any other patient
(e.g. age, menopausal status) or IBTR related (e.g. grade,
vascular invasion, margin status, receptor status)
parameters between the two groups. Three out of 35
(8.6%) and 7 out of 57 (12.3%) second local recurrences
occurred in the BCT + HDR iBT and the sMT group,
respectively. The 5-year actuarial rate of second local
recurrence was 7.4% after BCT + HDR iBT vs 17.5% after
sMT (p=0.11). The respective 5-year rates of regional
recurrence were 7.2% vs 5.3% (p=0.17). The 5-year
probability of DFS, CSS, and OS were 69.7% vs 73.5%
(p=0.79), 74.9% vs 80.5% (p=0.72), and 74.9% vs 69.6%
(p=0.73), respectively. At the time of analysis data on
cosmetic results were available for 31 patients (88.6%) in
the BCT + HDR iBT group. Among these, 3 (9.7%), 16
(51.6%), 5 (16.1%), and 7 (22.6 %) patients had excellent,
good, fair, and poor cosmetic results. Grade 2 and 3 late
skin toxicity occurred in 2 (5.7%) and 1 (2.9%) patients,
while grade 2 and 3 fibrosis developed in 9 (25.7%) and 1
(2.9%) patients. Asymptomatic fat necrosis was detected
in 11 (31.4%) women.
Conclusion
Second BCT + HDR iBT is a safe and feasible option for the
management of IBTRs resulting similar 5-year oncologic
outcomes compared to standard sMT. HDR iBT may
decrease the risk of second IBTR with acceptable cosmetic
results and low rate of late side effects.
Poster Viewing : Session 4: Brachytherapy
miscellaneous
PV-0183 Microbrachytherapy: even more localised dose
profiles?
R. Brown1,2, X. Franceries1,2 , M. Bardiès1,2
1INSERM, UMR1037 CRCT- F-31000, Toulouse, France
2Université Paul Sabatier, UMR1037 CRCT- F-31000,
Toulouse, France
Purpose or Objective
Owing to its intrinsic ability to deliver increased dose rates
to tumours whilst respecting organ at risk (OAR)
constraints, brachytherapy (BT) is being increasingly used
for the treatment of radioresistant tumours.
A new form of BT, microbrachytherapy (MBT), is proposed
for small tumours. For this treatment, the grains used in
BT are replaced by a solution containing β-emitters. More
injections can be used with MBT than grains with BT,
allowing for greater precision when targeting the tumour.
As with all forms of radiotherapy, treatment planning is
required. In this work, a method of generating optimal
MBT treatment plans is proposed.
Material and Methods
The non-dominated sorting genetic algorithm II (NSGA2)
[1] is used to generate treatment plans. This is a multi-
objective algorithm, permitting the objective functions to
be optimised independently.
Two objective functions were used: the first to minimise
the fraction of the tumour receiving less than the target
absorbed dose (60 Gy) and the second to minimise the
number of injections.
The algorithm was validated on a spherical tumour of
20 mm radius. 20 mm was chosen because it represents
the typical size of tumour that could be targeted with this
new technique.
Results
The evolution of the Pareto front during the optimisation
of the spherical tumour is shown in Figure 1. The
optimisation finished after 200 iterations (generations),
and so the final Pareto front represents the final results of
the optimiser.
Each point along the Pareto front represents a different
treatment plan. The front can be seen as a set of
compromises; it is impossible to decrease one objective
function without increasing another. This enables the user
to a posteriori decide relative objective importance and,
hence, choose the ideal treatment plan for each patient.
As an example, the treatment plan using 30 injections was
chosen. Its absorbed dose distribution through the central
slice is shown in Figure 2. To highlight the steep absorbed
dose gradient obtained with this treatment concentric
spherical shells, surrounding the tumour were also
included. Very satisfying treatment plans have been
defined using this new method of MBC.