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ESTRO 36
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Results
The median plane Dmax dose was 1.33 Gy (40% of 3.4Gy,
range 0.24-3.74 Gy) and showed moderate correlation
with grade of skin marks (0.505, p value 0.000). Similarly,
the closest distance of the CTV, prescription isodose
(Figure 2) and first-last dwell position was 1.74 (range
0.32-6.58), 1.09 (range 0.02-5.71) and 1.55 (range 0.25-
4.58) cm respectively all of which also showed moderate
correlation (-0.444, -0.471 and -0.495 respectively, p
value 0.000 for each). 70.1% (61/85) planes with Dmax
<40% of prescribed dose showed invisible or faint marks
and 72.1% (62/88) planes with Dmax >40% of prescribed
dose showed clear or prominent marks (p = 0.001). 86.4%
(19/22) planes with closest distance from CTV <0.7 cm and
91.4% (32/35) planes with closest distance from 85%
Isodose < 0.5 cm showed clear or prominent marks (p =
0.001). There was very high correlation between closest
distance from CTV 0.7 cm and closest distance from
isodose 0.5 cm (0.715). Taking 1.33 Gy (40% of prescription
dose per fraction) as a cut –off value for plane Dmax
resulting in clear-prominent implant marks on ROC curve
resulted in sensitivity 65% and specificity 60%.
Conclusion
This study highlights the need for minimization of dose to
the skin E-E site for reducing the risk of clear or prominent
skin marks which affect cosmesis. Wherever possible it is
advisable to edit the CTV to maintain a safe distance
between the prescription isodose from the skin E-E points.
However, larger sample size needs to be studied to
increase sensitivity and specificity of the E-E dose
constraint.
PO-0924 HDR boost in CT3 breast carcinoma with
neoadjuvant chemotherapy and conserving therapy
F. Romero
1
, J. Guinot
1
, M. Santos
1
, M. Tortajada
1
, P.
Santamaría
1
, L. Oliver
1
, V. Campo
1
, L. Arribas
1
1
Fundación Instituto Valenciano de Oncología, Radiation
Oncology, Valencia, Spain
Purpose or Objective
Locally advanced tumors with conservative surgery have a
higher relapse rate than early tumors. We analyze the
clinical outcome of HDR brachytherapy boost in patients
at high risk for tumor size, in terms of local control,
adverse effects and cosmetic results.
Material and Methods
Between February 1999 and October 2011, forty two
patients with 43 tumours, consecutively diagnosed with
cT3 infiltrative breast carcinoma were treated with
neoadjuvant systemic treatment, conservative surgery
and Whole Breast Irradiation (WBI) (50 Gy) followed by
High Dose Rate (HDR) interstitial brachytherapy boost (3 x
4.4 Gy at 85% isodose) in two days, with rigid needles.
Survival rates were calculated using the Kaplan-Meier
method, and the Cox proportional hazards model to
demonstrate the infuence of tumor response to
neoadjuvant chemotherapy.
Results
Median age was 48 years (30-77). Median follow-up was 95
months (8-201). The average lesion size was 56.7 mm (50-
100) before receiving any treatment. Local Control (LC) at
5 and 10 years was 87.1%. Overall Survival (OS) at 5 and
10 years was 85.7% and 72.4% respectively. Cancer-
Specific Survival (CSS) to 5 and 10 years was 85.7% and
75.8%. Disease-Free Survival (DFS) was 74,4% and 62,7% at
5 and10 respectively. Twenty-five tumor lesions (58 %) had
a complete response after neoadjuvance. There were no
significant differences in terms of local control depending
on the tumor response to neoadjuvant chemotherapy (p =
0.66). Nor concerning overall survival (p = 0.52) or cancer-
specific survival (p = 0.74). Grade 1 early toxicity was
38.5% and Grade 2 was 12.8%. There were no early Grade
3-4 toxicity. For late toxicity, 7/43 (16.3%) of patients had
fibrosis. Some of the patients reported induration from
surgery. There were no trophic skin changes. Good or
excellent cosmesis was recorded in 95.3% of patients.
Conclusion
Adding HDR brachytherapy boost to conserving therapy
allows preservation of breast in 87% of locally advanced
breast tumors (cT3) at 10 years, with good cosmetic
outcome.
This technique is effective and well tolerated.
PO-0925 Timing of post-implant analysis in permanent
breast seed implant: results from a serial CT study
E. Watt
1
, M. Peacock
2
, L. Conroy
1
, S. Husain
3
, A.
Frederick
1
, M. Roumeliotis
3
, T. Meyer
3
1
University of Calgary, Department of Physics &
Astronomy, Calgary- Alberta, Canada
2
University of British Columbia, Division of Radiation
Oncology, Vancouver- British Columbia, Canada
3
University of Calgary, Department of Oncology, Calgary-
Alberta, Canada
Purpose or Objective
Permanent breast seed implant (PBSI) is a novel, one-day
procedure for the treatment of early-stage breast cancer.
In this technique, stranded
103
Pd seeds are permanently
implanted in a volume surrounding the post-lumpectomy
seroma. Post-implant dosimetry is used to assess implant
quality, but the timing for this analysis is performed
inconsistently across cancer centres. The use of different
time points for analysis limits the ability to combine
results for long-term outcome studies. The purpose of this
study is to determine the most appropriate timing for
post-implant dosimetry.
Material and Methods
Ten patients underwent CT scans at 0 (immediately after),
15, 30, and 60 days post-implant. Each post-implant CT
scan was deformably registered to the planning scan to
obtain the seroma contour (clinical target volume, CTV)
using MIM Maestro
TM
(MIM Software, Inc., Cleveland OH).
This contour was reviewed and adjusted as necessary by a
radiation oncologist. Using the TG-43 dose calculation
formalism, a postplan was generated for each scan. For