Introduction
Breast cancer is one of the most common three cancer
types worldwide, as well as being the most common
cancer type among females.[] Adjuvant radiotherapy
is the standard treatment method in patients
undergoing breast-conserving surgery because it reduces
the risk of local recurrence and prolongs overall
survival.[-] Besides its important role in the
treatment regimen and numerous benefits, it shows
important side effects in normal tissue. Particularly,
the anterior heart is exposed to an intense dose during
left breast (LB) irradiation.[] Besides the anterior
heart, the left anterior descending coronary
artery (LADCA), lungs, and contralateral breast are
also exposed to considerable radiation.[] Darby et
al.[] reported that some changes may occur in the
heart exposed to ionizing radiation within followups.
Ischemic heart disease may develop within longterm
follow-up periods due to exposure of the heart
and LADCA to radiation dose and decrease the quality
of life. Besides, it has been detected that the risk
for various cardiac events, coronary artery disease,
and furthermore lung cancer has proceeded for long
years depending on treatment and dosage in the patients
who received radiotherapy (RT) for LB cancer
compared with right breast radiation.[] Because the
risk for fatal cardiovascular diseases increases due to
the proximity of the treatment field to the heart and
coronary vessels in LB cancer radiotherapy. The anterior
part of the heart and LADCA are exposed to
high doses during irradiation, particularly in the use
of classical treatment methods.[-]
Modern treatment techniques have been developed
and are currently still developed to decrease
heart, LADCA, lungs, and contralateral breast doses
in the radiotherapy of particularly LB cancer and
reduce the risk for potential subsequent cardiac toxicity,
ischemic diseases, radiation pneumonia, and
furthermore a secondary cancer.[] Respiratory
motion seriously affects dose distribution in RT for
LB cancer. Respiratory motion causes differences in
the distance between the volume that receives a high
dose and the heart. Deep inspiration breath-hold
technique (DIBH) eliminates the impact of breathing
motion by detaching the heart, LADCA, and lungs
from the target volume.[] However, the voluntary
breath-hold technique alone without definite standardization
may not be optimal because of differences
during treatment and between RT fractions. This
problem can be solved by management and monitoring of breathing. The use of an infrared surface marker
placed without the need for an invasive intervention
and a camera system that monitors this marker
during treatment and compares it with the reference
position has a higher safety than voluntary breathholding
or other systems.[-]
On the other side, it is known that the use of
intensity-modulated radiation therapy (IMRT) and
Volumetric Modulated Arc Therapy (VMAT) as
modern RT techniques provides a highly confirmed
dose distribution on the target volume and decreases
doses to organs-at-risk such as the heart and lungs.
[-] In recent years, IMRT is commonly used
instead of three-dimensional conformal RT (3DRT)
due to the achievement of regular dose distribution
on the target volume after breast-conserving surgeries
and reduction of doses to organs-at-risk in breast
cancer.[-] VMAT is one of the novel treatment
techniques and has been noticed to provide better
conformity and homogeneity on target volume coverage
with simultaneous modulation of multileaf collimator
(MLC) movement compared to IMRT and
also to present advantages in dose distribution to
organs-at-risk and delivery time reduction.[] Despite
the advantage of delivering a high dose to the
target volume and a low dose to the organs-at-risk,
it has been reported that standard VMAT may cause
malignancies by increasing doses to the contralateral
breast and contralateral lung compared with tangential-
based methods. Therefore, VMAT cannot be the
first treatment option in breast cancer.[] Tangential
VMAT (TVMAT) is a very novel treatment method
developed by modifications on VMAT considering
its disadvantages. Even though it seems similar to
tangential-based treatments, they provide high dose
at the target volume, low dose to organs-at-risk, and
delivery time reduction. Moreover, it eliminates the
disadvantages of VMAT in the contralateral organs.
Yu et al.[] have also reported that doses to OAR in
VMAT were higher than in TVMAT.
There are only a limited number of studies that compare
the techniques DIBH-TVMAT and free breath
(FB)-TVMAT based on respiratory monitoring. To our
knowledge, our comparison will be the study with the
largest number of patients that has dosimetrically compared
TVMAT applied using the DIBH technique with
TVMAT applied using the FB technique. In addition,
it has been aimed to demonstrate that TVMAT applied
using the DIBH technique reduces the dose to organs
at risk such as the heart, left lung, LADCA, and right
breast and can be safely implemented.
Methods
Sixty-one patients were included in the study. The patients
were selected according to the following inclusion
criteria:
The patients;
1. who had undergone breast-conserving surgery between
January 2016 and January 2020 and received
adjuvant RT
2. who could hold their breath in deep inspiration after
breath-hold guidance
3. whose CT images could be taken in both deep inspiration
and free-breath
4. with good performance status
The exclusion criteria for the patients were as follows:
1. who could not hold their breath in deep inspiration
after breath-hold guidance
2. who had undergone mastectomy
3. who had previously received RT for breast or another
field
Breast RT was performed in 44 patients, whereas
17 patients received RT to breast, Level I, II, and III
axillary lymph nodes, supraclavicular lymph nodes
(SCLN), and internal mammary lymph nodes (IMLN).
All the patients who received lymph node irradiation
were Stage II or III. The patients were fixed with hands
over head in the supine position on the carbon fiber
breast board using elbow boards. Radiopaque markers
were placed into the imaging area before the imaging
procedure. Computed tomography (CT) slices were acquired
with a 16-slice CT scanner (Siemens Somatom
Emotion Duo). The CT acquisition slice was 3 mm in
thickness. The imaging field started from the first cervical
vertebra of the upper spine and elongated to the
second lumbar vertebra of the lower spine.
Breath-Hold Guidance
Each patient was guided about breath-holding by a
training nurse one week before CT imaging. Breathhold
guidance involved instruction of the patients on
how to hold their breath and how to initiate breathing.
CT scans were obtained by holding breath at
deep inspiration and free-breathing in the successful
patients in breath-holding. The breath-holding level
was encountered by breath-hold monitoring with an
infrared reflecting block and cameras inserted into
the xiphoid process using the real-time position management
(RPM) System (Varian Medical System, Palo
Alto, USA). The field of the infrared reflecting block
was marked on the patient's skin. A test procedure was
performed prior to CT imaging by having the patients hold their breath twice for 20 seconds. CT imaging was
initiated in DIBH in the patients who completed the
test procedure successfully. At the onset of the imaging
session, a gating window was specified as 1.5 mm below
and above the breath-hold level to medium to be used
during treatment. Immediately after this procedure,
free-breath images were obtained in the same position.
CT scan images, the respiratory curve, and gating window
were recorded after CT imaging and analyzed in
the Eclipse Version 13.6.23 Treatment Planning System
(Varian Medical System, Palo Alto, USA).
The Determination of the Target Volume and
Organs-at-risk
The determinations of the organs-at-risk and target
volume were carried out according to the delineation
guidelines of the Radiation Therapy Oncology Group
(RTOG)[] and the Danish Breast Cancer Cooperative
Group.[] Primarily the heart, LADCA, right and left
lungs, esophagus, right breast, and spinal cord were contoured
as the organs-at-risk. The clinical target volume
(CTV) was contoured for each patient by the same radiation
oncologist in both DIBH and FB. The CTV included
LB glandular tissue of the patients who would receive
only breast irradiation whereas LB glandular tissue,
Level I-III lymph nodes, IMLN, and SCLN were included
in the patients who would receive irradiation to the
regional lymph nodes. The breast glandular tissue was
determined utilizing the sternum and mid-axillary line
at medial and lateral aspects in the CT images, respectively.
The latissimus dorsi muscle was excluded from
the treatment field. All the patients received an additional
boost dose to the tumor bed. Seroma and surgical
clips were contoured for the determination of the tumor
bed to be applied boost dose (gross tumor volume after
lumpectomy). The cranial and caudal margins of SCLN
were contoured as the caudal aspects of the cricoid cartilage
and clavicular head, respectively. The thyroid gland
and trachea were definitely excluded from the treatment
field. Axillary lymph nodes were contoured taking the
pectoralis major and minor muscles as a reference. The
cranial and caudal margins of IMLN were specified as
the superior aspect of the 1st rib and cranial aspect of the
4th rib, respectively. The planning target volume (PTV)
was generated by adding a 5-mm margin to the CTV
through three-dimensional expansions. The PTV was
cropped from the skin by a 3-mm margin.
Treatment Planning
All patients were distributed into two groups. The
treatment plans were created separately for each patient
both in DIBH and FB.
DIBH-TVMAT and FB-TVMAT plans were designed
using a mono-isocentric technique with two
partial arc rotations for patients whose only breast and
tumor bed would be irradiated. The first arc started at
275.8-309.3 degrees and stopped at 131.6-172.5 degrees
in DIBH-TVMAT plans. The second arc was fully
inverted to the first arc. The same entrance and exit
angles were used in FB-TVMAT plans. The collimation
angles of 30 and 330 degrees were used in the first and
second arcs, respectively.
DIBH-TVMAT and FB-TVMAT plans were also
designed using a mono-isocentric technique with two
partial arc rotations for patients whose breast, tumor
bed, and RLN would be irradiated. The first arc started
at 285-311.4 degrees and stopped at 124.3-175 degrees
in DIBH-TVMAT plans. The second arc was fully inverted
to the first arc. The same entrance and exit angles
were used in FB-TVMAT plans. The collimation
angles of 30 and 330 degrees were used in the first and
second arcs in this group, respectively.
The total dose defined for the breast was 50 Gy
with 2 Gy per fraction per day for the group in which
RT was applied to only the breast. A dose of 60 Gy
with 2.4 Gy per fraction per day was defined for the
tumor bed by the simultaneous integrated boost
(SIB) technique. The purpose of the treatment plan
was described as receiving 95% of the defined dose
by at least 98% of PTV applied as 50 Gy whereas that
was receiving 95% of the defined dose by at least 98%
of PTV applied as 60 Gy.
The total dose defined for breast+RLN was 50 Gy
with 2 Gy per fraction per day for the group in which
RT was applied to breast and RLN. A dose of 60 Gy
with 2.4 Gy per fraction per day was defined for the
tumor bed by SIB technique. The purpose of the treatment
plan was described as receiving 95% of the prescribed
dose by at least 98% of PTV applied as 50 Gy
whereas that was receiving 95% of the prescribed dose
by at least 98% of PTV applied as 60 Gy.
The treatment planning was created for each patient
primarily with DIBH-TVMAT. The treatment
plans were created using Eclipse Version 13.6.23 Treatment
Planning System (TPS) (Varian Medical System,
Palo Alto, USA). The treatment plans were performed
using 6MV photon energy. Gantry settings were the
same for DIBH-TVMAT and FB-TVMAT. The first
essential target of the treatment plan was 98% coverage
of PTV by 98% of the defined dose. The second
essential target of the plan was to keep the doses at
the lowest possible level for the organs-at-risk while
the first essential target was achieved. No bolus dose was administered to any of the patients. The target
volumes, dose concentrations for the organs-at-risk,
and our priorities were as shown in the table (Table
1). The optimization was stopped when these criteria
were met, and the plan was accepted as the final plan
(Figs. 1, 2). Similar conformity and homogeneity were
achieved for each plan. In addition, quality assurance
(QA) was carried out for each plan. The grid size for
dose calculation was 2.5 mm. The progressive resolution
optimizer (Version 13.6.23) and analytical anisotropic
algorithm (Version 13.6.23) were used for the
optimizations of TVMAT.
Table 1 Critical organ dose limitations for DIBH-TVMAT
and FB-TVMAT
Fig. 1. The dose distribution in the axial, sagittal and coronal views of the case applied 50
Gy to the breast and 60 Gy to the tumor bed by simultaneous integrated boost (SIB)
technique after left breast-conserving surgery. (a) TVMAT plan with deep inspiration
breast-hold technique. (b) TVMAT plan with free-breathing technique.
TVMAT: Tangential-based volumetric modulated arc therapy.
Fig. 2. The dose distribution in the axial, sagittal and coronal views of the case applied 50
Gy to the breast and regional lymph nodes, and 60 Gy to the tumor bed by simultaneous
integrated boost (SIB) technique after left breast-conserving surgery. (a)
TVMAT plan with deep inspiration breast-hold technique. (b) TVMAT plan with
free-breathing technique.
Dosimetric Evaluation
All DIBH-TVMAT and FB-TVMAT plans were evaluated,
and dosimetric parameters were determined.
The heart volumes that received 5, 10, 25, and 30 Gy
doses, mean and maximum doses (V5, V10, V25,
V30, Dmean, Dmax), and the values of LADCA (V4, V5,
V10, V25, V30, Dmean, Dmax), left lung (V5, V10, V20),
right lung (Dmean, D2%), and right breast (Dmean) as the
organs-at-risk were obtained from the dose-volume
histogram (DVH). These values were compared comprehensively
only in the group that received irradiation
to breast and breast+RLN (Figs. 3, 4). In addition,
dosimetric analyses and comparisons were carried out
for the organs-at-risk after SCLN irradiation for these
two groups. Equivalent doses of 2 Gy fractionation
(EQD2) were calculated for the organs-at-risk and target
volumes to perform an accurate dosimetric comparison
since the SIB technique was implemented.
Fig. 3. The dosimetric comparison between dose-volume histograms of organs-at-risk and target volumes in DIBH-TVMAT
and FB-TVMAT plans of the case applied 50 Gy for the breast and 60 Gy for the tumor bed after left breastconserving
surgery.
DIBH: Deep inspiration breath-hold technique; TVMAT: Tangential-based volumetric modulated arc therapy; FB: Free-breath.
Fig. 4. The dosimetric comparison between dose-volume histograms of organs-at-risk and target volumes in DIBH-TVMAT
and FB-TVMAT plans of the case applied 50 Gy for the breast and regional lymph nodes and 60 Gy for the
tumor bed after left breast-conserving surgery.
Statistical Analysis
Data were analyzed using IBM SPSS Version 24.0
(SPSS Inc., IL, USA) statistical software. The distribution
normality of the continuous variables was tested using visual (histogram and probability analyses) and
analytical (Kolmogorov-Smirnov/Shapiro-Wilk tests)
methods. Mean and standard deviation were used for
normally distributed data. The doses determined for the treatment plan of each patient group created using
DIBH-TVMAT and FB-TVMAT were analyzed with a
Paired-sample T-test. The dosimetric analyses following supraclavicular irradiation between two groups were
carried out using an Independent T-test. A p-value of
<0.05 was accepted as the statistical significance level.
Informed Consent and Ethics Committee Approval
Informed consents were obtained from all patients. Institutional
evaluation board approval and Ethics Committee
Approval were obtained for the present study.
Results
The median age of the 44 patients who received RT for
only the breast was 54 (36-74) years. Invasive ductal carcinoma was present in 33 (75%) of the patients who
received RT for the breast. Of those patients, 22 (50%)
had a Grade 2 tumor, whereas 25 (56.8%) patients
were evaluated to be in the Luminal A group. Thirty
(68.2%) of the patients who received RT for the breast
were Stage IA. The median age of the 17 patients who
received RT for the breast+RLN was 49 (29-63) years.
Ten (58.8%) were premenopausal. The patient and tumor
characteristics were summarized in Table 2.
Table 2 Patient and tumor characteristics
The Comparison between DIBH-TVMAT and
FB-TVMAT in the Patients Who Received RT for
Only the Breast
The values obtained for the organs-at-risk and PTV
were listed in Table 3.
Table 3 Dosimetric parameters and differences between DIBH-TVMAT and FB-TVMAT plans
regarding doses to organs-at-risk including heart, left lung, right lung and right
breast obtained from dose-volume histogram in the patients applied radiotherapy
for only the breast (Δ)
Heart and LADCA: The comparison between the two
plans regarding heart values revealed that the mean heart
dose was 5 Gy in the DIBH plan, whereas it was found
to be 8.8 Gy in the FB plan (p=0.000). According to this
result, the mean heart dose decreased by 3.7 Gy (42%)
after the implementation of DIBH. The heart volume that
received 25 Gy was 1.2% in the DIBH plan, whereas that
volume was 7% in the FB plan (p=0.000). The maximum
heart doses were 36.4 Gy and 49.3 Gy in the plans applied
with DIBH and FB techniques (p=0.000), respectively.
These results indicated a 25% reduction. The comparison in terms of mean LADCA doses showed that the mean
LADCA dose in DIBH plans was 14.8 Gy, whereas it was
21.9 Gy in FB plans. An increase of averagely 7.1 Gy corresponding
to 32% was detected in FB plans (p=0.000).
An average 22% reduction was encountered in LADCA
maximum doses in DIBH plans.
Ipsilateral lung, Contralateral lung, and right
breast: Ipsilateral lung volumes that received 5 Gy in
DIBH and FB plans were found to be 59% and 65%,
respectively (p=0.001). The V20 value for the DIBH
technique was 18.6% Gy, whereas that value was 19.7%
Gy for the FB technique (p=0.003). Thus, an improvement
of 5% was achieved by the DIBH technique in
V20 values. Even though the lung volume that received
10 Gy showed a 2% decrease by the DIBH technique,
no statistical significance was detected (p=0.2).
The mean right lung values for DIBH and FB
treatment plans were found to be 3.3 Gy and 3.9 Gy,
respectively (p=0.000). The ipsilateral lung D2% value
was detected to be 11.9% in DIBH plans. That value
corresponded to an average dose reduction of 4%
compared with FB plans. However, no statistical significance
was determined (p=0.4).
A 0.5 Gy (7%) reduction was detected between
DIBH and FB plans regarding the mean right breast
dose (p=0.003).
The Comparison between DIBH-TVMAT and FBTVMAT
in the Patients Who Received RT for the
Breast+Regional Lymph Nodes
The values obtained for the organs-at-risk and PTV
were listed in Table 4.
Table 4 Dosimetric parameters and differences between DIBH-TVMAT and FB-TVMAT plans
regarding doses to organs-at-risk including heart, left lung, right lung and right
breast obtained from dose-volume histogram in the patients applied radiotherapy
for the breast and regional lymph nodes (Δ)
Breast and LADCA: The mean heart dose was
found to be 5.5 Gy in the treatment plan using the
DIBH technique. A dose reduction of 3.4 Gy corresponding
to 38% was encountered compared with
FB (p=0.000). The most significant dose reductions
were noticed in the values of the volume that received
25 Gy. The mean values in DIBH and FB plans were
6.4% and 1.2%, respectively. This result indicated an
81% reduction (p=0.000). The same reduction was
determined also in the values of heart V5, V25, and V30. The comparison regarding mean LADCA doses
showed reductions of 6.2 Gy (27%) and 11.4 Gy (23%)
in the Dmean and Dmax values, respectively (p=0.000;
p=0.000). A reduction of 27% was also detected in the
volume that received a 25 Gy dose (V25) compared
with the FB plan (V25) 27% (p=0.000).
Ipsilateral lung, Contralateral lung, and Right
Breast: The most surprising results were obtained in
the left lung doses of the group that received breast-
+RLN irradiation. The comparison between DIBH and
FB plans indicated an average 7% reduction only in the
lung volume that received a 5 Gy dose, and this reduction
was found statistically significant (p=0.001). However,
the reduction in the values of V10 and V20 was
not statistically significant.
The evaluation of the right lung doses revealed
a reduction of 0.8 Gy corresponding to 18% in the
mean lung dose applied in the DIBH plan (p=0.007).
The comparison between DIBH and FB plans regarding
D2% values showed a 9% reduction; however, that
result was not found statistically significant (p=0.2).
Another noticeable organ-at-risk was the right breast.
A 0.3 Gy reduction was detected in the mean contralateral
breast dose by the comparison between
DIBH and FB plans; however, this reduction was not
evaluated to be statistically significant (p=0.2).
The Comparison between the Effects of DIBHTVMAT
and FB-TVMAT Techniques Applied in
Supraclavicular Lymph Node Irradiation for the
Organs-at-risk
Heart and LADCA: The integration of SCLN into the
treatment field had no impact on the heart volumes that
received 10, 15, 25, and 30 Gy doses, as well as Dmean
and Dmax dose values, in the irradiated patients using the
DIBH-TVMAT technique. However, mean V5 values
were found to be 37.5% and 29.5% in the DIBH-TVMAT
plan, and the only increased value of V5 was statistically
significant after SCLN irradiation (p=0.002) (Table 5).
On the other side, differently from the DIBH-TVMAT,
no impact of SCLN irradiation using the FB-TVMAT
plan was encountered on the dosimetric parameters of
the heart. Similarly, with heart doses, a statistically significant
increase was detected only in the V5 value using
the DIBH-TVMAT plan after SCLN irradiation in the
comparison between LADCA doses regarding SCLN irradiation
(p=0.002). No impact of SCLN irradiation using
the FB-TVMAT plan was encountered on LADCA
regarding the dosimetric parameters (Table 6).
Table 5 The dosimetric parameters of the organs-at-risk
including heart, left lung, right lung and right
breast obtained from dose-volume histogram
for DIBH-TVMAT plan in the patients with and
without supraclavicular lymph node RT
Table 6 The dosimetric parameters of the organs-at-risk
including heart, left lung, right lung and right
breast obtained from dose-volume histogram for
FB-TVMAT plan in the patients with and without
supraclavicular lymph node RT
Ipsilateral Lung, Contralateral Lung, and Right
Breast: SCLN irradiation was found to significantly
affect mean left lung, V5, V10, and V20 values in
both DIBH-TVMAT and FB-TVMAT plans (p=0.000; p=0.000; p=0.02, respectively). An adverse result was
monitored in the right lung. SCLN irradiation showed
no statistically significant effect on right lung Dmean
doses with DIBH and FB planning (p=0.2; p=0.2, respectively).
Even though reductions were encountered
in mean right breast doses using both DIBH and FB
plans, these reductions were not statistically significant
(p=0.5; p=0.8, respectively) (Table 5, 6).
Discussion
The present study was carried out using the RPM system
as one of the most reliable and easily applicable
methods of the DIBH technique. All patients showed
compliance with the DIBH procedure throughout
the study. To our knowledge, it is the largest singlecenter
patient study in which DIBH was integrated
into the TVMAT technique with breath monitoring,
and dosimetric analyses were carried out in patients
irradiated for breast+RLN after breast-conserving
surgery. The impact of SCLN irradiation has also
been evaluated comprehensively in the study. Both
DIBH-TVMAT and FB-TVMAT planning were reviewed,
and dosimetric parameters of the doses to
organs-at-risk were compared. According to the
study outcomes, both whole-breast and breast+RLN irradiations applied in combination with TVMAT
and DIBH were found to significantly reduce the
doses applied to the heart, LADCA, ipsilateral, and
contralateral lungs. In both DIBH and FB planning,
dramatic decreases were noticed not only in mean
heart doses but also in V5, V10, V25, V30, and Dmax
values of the heart in both groups. The reduced doses
of the contralateral breast were detected by the implementation
of DIBH in patients irradiated for only
the breast, while a 5% reduction was monitored in
patients irradiated for breast+RLN; however, this reduction
was not found statistically significant.
Many retrospective studies have demonstrated that
RT implemented to breast+RLN using the DIBH technique
in LB cancer patients caused significant reductions
in doses applied to the heart and coronary veins.
[-] Al-Hammadi et al.[] included patients who
had undergone both breast-conserving surgery and
mastectomy in their single-center study that evaluated
dosimetric parameters in patients who applied the voluntary
DIBH technique. In some patients, the RLN was
included in the irradiation area, while in other parts, RT was applied only to the breast/chest wall. In that study,
patients were not divided into groups for the evaluation
of dosimetric parameters, although different fields
were irradiated, and statistical analyses were carried
out for all patients. Similarly, with our study, the mean
heart dose regressed from 6.1 Gy to 3.2 Gy, indicating
a 50% reduction was encountered. The mean LADCA
doses in DIBH and FB plans were found to be 23 Gy
and 14.8 Gy, respectively. The differences between V10,
V20, and V30 values were found statistically non-significant
according to the dosimetric comparison between
voluntary breath-hold and free-breathing plans
in the left lung. However, right lung and right breast
doses were not tested. In our study, left lung V5 and
V20 values were detected to be reduced after DIBHTVMAT
planning in the group that implemented RT
for only the breast, whereas significant reductions were
determined only in V5 values of the group irradiated
for breast+RLN. Dmean values of the right lung and right
breast were monitored to be significantly decreased
by the DIBH-TVMAT technique in the group that
implemented RT for only the breast. Contrarily, only
the right lung Dmean dose significantly decreased in the
group that applied RT to breast+RLN.
Al-Hammadi et al.[] also determined that the
mean left lung and V20 values decreased after the exclusion
of the supraclavicular fossa from the RT field in
patients who applied both DIBH and FB. On the other
side, our study results indicated a significant decrease
in V5, V10, and V20 values of the ipsilateral lung in
both DIBH-TVMAT and FB-TVMAT plans. Additionally,
similar to this study, the exclusion of SCLN
from the RT field had no impact on mean and maximum
heart doses in the planning with both DIBH and
FB. Furthermore, dosimetric parameters of the right
lung and right breast were not affected by the exclusion
of SCLN from the RT field. Only heart V5 and LADCA
V5 values were detected to be increased after the addition
of SCLN to the irradiated field in DIBH planning.
Even though most parameters appeared to be correlated,
some values seemed to be higher in that study. We
used the parameters in our study obtained by the implementation
of 60 Gy RT to the tumor bed using the
SIB technique. Al-Hammadi et al.[] implemented 50
Gy RT in all patients, and calculations were carried out
on this dosage in their study. The groups were not differentiated
in performing dosimetric evaluations and
statistical analyses. This aspect is an important factor
for the different outcomes of their study.
Lin et al.[] also included patients with both left
and right breast cancer in their large case series. In this
study, the comparisons were conducted without differentiation
regarding treatment planning techniques and
tumor laterality. The concurrent evaluation of the right
and LB treatment plans indicated a 50% reduction in
mean heart doses using DIBH compared with FB. In
our study, an improvement was achieved in both heart
and organ-at-risk doses after using DIBH, according to
the evaluation of only LB.
On the other hand, 3-D conformal, IMRT, hybrid
IMRT, and standard VMAT techniques were compared
in some studies.[-] The applicability of novel techniques
has been researched also in recent studies.[-]
In one of those studies, Dumane et al.[] treated breast
cancer patients with a breast implant using DIBH-TVMAT
while regional lymph nodes were also added to the
RT field and compared dosimetric parameters. In their
study, they implemented 50 Gy RT in all patients. Mean
heart doses in DIBH and FB plans were 8.2 Gy and 5.3
Gy, respectively. In other words, a mean reduction of
2.9 Gy was detected. In our study, the mean heart dose
decreased from 8.9 Gy to 5.5 Gy according to the comparison
between DIBH-TVMAT and FB-TVMAT plans
in patients who received RT to breast+RLN. In other
words, a mean reduction of 3.4 Gy was determined. In addition, a boost dose of 60 Gy RT was administered to
the tumor bed. Similarly, in this study, the reduction in
the value of V5 of the ipsilateral lung using the DIBHTVMAT
plan was significant, whereas the reduction
in the V20 value was statistically non-significant in the
group that had RLNs added to the RT field. However,
the contralateral breast Dmean dose reduction was not
found statistically significant in that study, whereas we
identified a decrease in contralateral breast Dmean values.
Virén et al.[] implemented 50 Gy RT to the breast
in their study on LB cancer and compared the standard
tangential field-in-field (FinF) plan, tangential intensity-
modulated radiotherapy plan, TVMAT plan with
two dual arcs, and continuous VMAT (CVMAT) plan
with a dual arc using FB without the DIBH technique.
They reported that CVMAT decreased ipsilateral lung,
heart, and LADCA doses more than other techniques,
whereas it increased the low doses applied to the contralateral
lung and breast volumes. Contrarily, they
stated that TVMAT increased both dose coverage and
homogeneity without increasing low contralateral lung
and breast dose-volumes. They noted that TVMAT
could be a safe treatment method for this reason. Yu et
al.[] have shown the superiority of the TVMAT technique,
particularly in patients that had RLNs added to
the treatment field. TVMAT planning has been recommended
considering its contribution to dose homogeneity
and its therapeutic effect.
Yu et al.[] included 14 patients who underwent
breast-conserving surgery and 50 Gy RT to the breast
in their study and compared DIBH-TVMAT and FBTVMAT
planning. The use of 4 partial arcs was preferred
in the study. We used 2 partial arcs in our study
to shorten the treatment process and thereby increase
the quality of breath-holding. In that study, the mean
heart dose after 50 Gy RT in DIBH-TVMAT and FBTVMAT
plans were 7.9 Gy and 3.2 Gy, respectively. A
50% reduction was observed in ipsilateral lung V30
value, whereas mean contralateral lung and contralateral
breast doses were similar to our study.[]
Another crucial subject is the system applied for
breath-holding. Voluntary breath-holding is a system
completely left to the patient"s initiative without the requirement
of any equipment and progresses with coaching
instructions. It can be performed in institutions that
do not have adequate equipment. Bartlett et al.[]
compared ABD-DIBH and voluntary BH in their study
carried out with 23 patients and reported that set-up errors
were insignificant. However, although these errors
appear to be insignificant, errors that may emerge due
to the patient"s initiative should not be underrated. The ABC system is a spirometer-based system. It forces the
patient to hold their breath. Therefore, it may be discomforting
for the patient. Besides, it is not suitable
for patients with anxiety. This situation may affect dose
distribution. The patient does not experience such complaints
with the use of the RPM system. Hamming et
al.[] evaluated the accuracy and applicability of surface-
guided RT accompanied by cone-beam CT-based
monitoring. The comparison between CBCT and SGRT
data revealed positioning errors below 5 mm, and SGRT
has been reported to be a reliable option for patients.
The limitation of our study was the non-use of
an intravenous contrast agent during CT simulation.
Wennstig et al.[] evaluated the interobserver differences
during contouring coronary arteries. They
reported in their study that minimal differences may
occur between observers in contouring performed
without contrast enhancement.
Conclusion
Compared with FB-RT, the DIBH technique provides
significant dose reduction applied to the heart, LADCA,
ipsilateral lung, contralateral lung, and contralateral
breast. The DIBH technique, accompanied by RPM, not
only increases patient comfort but also minimizes both
intrafractional and interfractional variability thanks to
monitoring. Thereby, it assures regular dose distribution
in the target volume and decreases toxicity. Besides, the
TVMAT technique increases homogeneity and dose
coverage as well as VMAT. However, it does not increase
the doses to the volumes of the organs-at-risk in contrast
to VMAT. The technique in which DIBH was integrated
into TVMAT in LB cancer patients may be accepted as
the standard treatment approach in due course.
Ethics Committee Approval: The study was approved by
the Erciyes University Clinical Research Ethics Committee
(no: 2020/31, date: 15/01/2020).
Authorship contributions: Concept - D.A., M.T.A.; Design
- D.A., M.T.A.; Supervision - D.A., M.T.A.; Funding
- D.A., M.T.A.; Materials - D.A., M.T.A.; Data collection
and/or processing - D.A., M.T.A.; Data analysis and/or interpretation
- D.A., M.T.A.; Literature search - D.A.; Writing
- D.A.; Critical review - D.A., M.T.A.
Conflict of Interest: All authors declared no conflict of interest.
Use of AI for Writing Assistance: Not declared.
Financial Support: None declared.
Peer-review: Externally peer-reviewed.
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