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ESTRO 36 2017
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EP-1834 Dose to internal mammary nodes compared to
dose to heart and lung for breast cancer patients
M. Berg
1
, M. Christensen
2
, M. Andersen
2
, N. Kiilerich
2
1
Vejle Hospital, Department of Medical Physics, Vejle,
Denmark
2
University College Lillebaelt, Department of Radiology
and Radiotherapy, Odense, Denmark
Purpose or Objective
Prioritization of internal mammary nodes (IMN) over dose
to the heart and ipsilateral lung for patients having left-
sided radiotherapy (RT) to the residual breast and regional
lymph nodes left-sided breast cancer has changed in
Denmark after the data from the DBCG-IMN study was
released in 2014 [1]. In that study it was shown that in
general patients benefit more from having IMN included in
the fields compared to the risk of ischemic heart disease.
We wanted to evaluate the clinical relevant changes
caused by this new practice in our clinic.
Material and Methods
The dose plans for 45 consecutive patients (20 patients
before and 25 after the new practice, respectively) were
retrospectively evaluated with respect to V5Gy, V20Gy,
V40Gy and mean dose for the heart (MHD), V20Gy and
mean dose (MLD) for the ipsilateral lung and V45Gy
(prescription dose) for IMN. According to national
guidelines the following constraints should be aimed at:
V20Gy ≤ 10% and V40Gy ≤ 5% for the heart, V20Gy ≤ 35%
for the ipsilateral lung and MLD ≤ 18 Gy. After the change
according to local guidelines V20Gy should not exceed 40%
for the ipsilateral lung.
Results
Changing the clinical practice trying to increase V45Gy to
IMN has resulted in higher median dose to the heart for all
parameters investigated – see Table 1. Median MHD
increased from 1.50 Gy to 1.85 Gy corresponding to 16.4%
and 20.1% increase in rate of major coronary event,
respectively [2]. The V20Gy and V40Gy constraints for the
heart was violated in one and two cases compared to four
and three before and after, respectively. V20Gy for the
ipsilateral lung was larger than 35% for one patient before
compared to seven patients after the change. V20Gy never
exceeded 40% for any patient. MLD was larger than 18 Gy
for one patient before and in no cases after. The median
volume of IMN receiving the prescription dose (45 Gy) of
higher increased from 74.7% to 87.8%.
Conclusion
Paying more focus to increasing V45Gy for IMN resulted in
better target coverage at the expense of higher doses to
heart and ipsilateral lung. However the increased dose to
heart and lung is believed to be justified by better survival
due
to
better
target
coverage
of
IMN
.
[1] CT-planned internal mammary node radiotherapy in
the DBCG-IMN study - benefit versus potentially harmful
effects, Thorsen
et al
, Acta Oncologica, 2014; 53: 1027-
1034
[2] Risk of Ischemic Heart Disease in Women after
Radiotherapy for Breast Cancer, Darby
et al
, N Engl J Med
368:11 987-998
EP-1835 Independent verification of treatment
planning system calculations
E. Dąbrowska
1,2
, B. Brzozowska
1
, A. Walewska
2
, P.
Kukolowicz
2
, A. Zawadzka
2
1
Faculty of Physics University of Warsaw, Department of
Biomedical Physics, Warsaw, Poland
2
Maria Sklodowska-Curie Memorial Cancer Center and
Institute of Oncology, Department of Medical Physics,
Warsaw, Poland
Purpose or Objective
In accordance to the EURATOM directive 97/43 (EURATOM,
1997) there must be an independent dose verification
procedure for quality assurance in all clinical radiotherapy
routines. Referring to Report of AAPM Task Group 114, this
procedure can be performed e.g. by second treatment
planning system (TPS). The aim of this study was to
compare and quantify the differences in dose distribution
obtained with two commercially available radiotherapy
TPS: the Eclipse (Varian) and the Oncentra MasterPlan
(Nucletron).