Localisation of Tumor Bed and Its Impact on Dosimetry for Tumor Bed Boost Irradiation in Patients Treated With Breast Conserving Surgery Using Different Techniques
Conditions: Breast Carcinoma
Sponsor: Tata Memorial Centre

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Localisation of tumor bed and its impact on dosimetry for tumor bed boost 
irradiation in patients treated with breast conserving surgery using different 
techniques 
 
Principal Investigators: Dr. Ashwini Budrukkar 
 
 
 
 
Co-Investigators:Dr.ArbaazPatwe 
Dr.TabassumWadasadawala 
Dr. Rajiv Sarin 
Dr. Rakesh Jalali 
Dr.Santam Chakraborty 
Mr.RiturajUpreti 
Mrs.UditaUpreti 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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Introduction: 
For patients with early stage invasive disease, surgery can either be a breast conserving 
resection of the primary tumor or a mastectomy. Several randomised prospective clinical 
trials have indicated that breast conserving surgery with whole breast radiation provides 
long term outcomes equivalent to those of mastectomy1,2,3,4. The goal of breast conserving 
surgery is to remove the primary tumor with surgical margins that are free from invasive or 
insitu disease. A secondary goal is to provide the best possible cosmetic outcome without 
retraction, nipple displacement, or excess volume loss from the procedure. For some 
women with larger breasts, oncoplastic surgery can be used in which local tissue 
rearrangements are performed at the time of surgical resection to maintain optimal breast 
aesthetics 
Radiation is essential component of breast conserving therapy. The use of RT improved 
recurrence free, breast cancer specific survival and overall survival in both patients with 
negative and positive axillary lymph nodes in the most recent metaanalysis of Early Breast 
CancerTrialists Collaborative Group(EBCTCG)5 which included trials begun before 2000.It 
included data from 42080 patients with breast cancer treated in 78 clinical trials that 
investigated locoregional treatments between 1952 and 1995.Among those patients were 
7311 patients treated in 10 trials comparing radiation vs no radiation after breast conserving 
surgery and 9933 patients treated in 25 trials comparing radiation vs no radiation after 
modified radical mastectomy. In the trials that investigated radiation as a component of 
breast conserving therapy, radiation was shown to reduce the risk of local recurrence by 
two thirds and to improve the absolute 15 year overall survival rate by 6% (41% versus 
35%).Similarly for patients with positive lymph nodes treated with modified radical 
mastectomy, radiation reduced the risk of locoregional recurrence rate by 21% at 15 
years(29% versus 8%), which was associated with a 5% decrease in the 15 year breast cancer 
mortality rate (60% versus 55%).A more recent update of the analyses continues to 
demonstrate locoregional and survival advantages for radiation therapy 
Even if surgical margins are negative after BCS, 30-40% risk of microscopic tumor cells in 
tumor bed. Most recurrences (65-80%) are located in vicinity of tumor bed as shown in 
EORTC6 trial and NSABP-06 trial. It is therefore important to ensure the tumor bed lies well 
inside the treatment volume encompassed by tangential fields to whole breast and 
subsequent tumor bed boost. There is also a pathological basis for giving boost to tumor 
bed-residual tumor foci have been reported in 1-2 cm in around 20-25% 
patients/histopathological specimens. 
The EORTC 22881-108827 trial studied the effect of addition of a boost dose on the primary 
tumor bed after lumpectomy in breast conserving treatment for breast cancer. It included 
5318 patients who received whole breast irradiation after lumpectomy and then 
randomised to boost of 16 Gy to tumor bed or no boost. The median follow up was 10.8 
years. It was found that 47% of local recurrences were in primary tumor bed, 10% in scar, 
29% outside original tumor area and 13% were diffuse. At 10 years, the cumulative 
incidence of local recurrence was 10.2% versus 6.2% for the 0 Gy and the 16 Gy boost 
groups (p< 0.0001). 

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Regarding surgical techniques for BCS, two main methods can be distinguished: open cavity 
and closed cavity technique. In the former only the superficial part of the cavity is closed 
allowing the formation of seroma. During closed cavity technique a full thickness closure is 
performed by suturing the deep and superficial layers of the surrounding breast tissue. In 
this case seroma does not develop and the target volume definition can be much more 
difficult. 
Oncoplastic surgery represents a special form of closed cavity breast conservation 
tumorsurgery.The advantage of oncoplastic surgery is the combination of tumour excision 
and immediate reconstructive surgery. Because of the excellent cosmetic results oncoplastic 
surgery has become more frequent in the past years. However adjuvant radiotherapy 
procedures have to face the possibility of breast tissue dispacements at risk of residual 
tumor cells, influencing the post operative target definition for partial breast irradiation 
 
The tumor beds of medially and laterally located tumors are particularly prone to 
underdosage if surface landmarks are used as fiducial points for whole breast RT planning. It 
is therefore very important to localise the tumor bed even for whole breast RT 
planning.Clinical planning of tumor bed boost volume based on preoperative imaging, 
surgical note and breast scar position is very unreliable. Increasingly the breast scar is placed 
often some distance from the tumor for wire guided localisation biopsy or better cosmetic 
outcome. In addition the practice of oncoplastic surgery where breast tissue is repositioned 
following wide excision to minimise the surgical deficit is becoming standard of care. In this 
situation the preoperative imaging bears very little final relation to tumor bed. 
Computed tomography and ultrasonography can use the seroma as a surrogate for tumor 
bed position, but there are limitations. First, the seroma is only clearly defined in only about 
quarter of patients. Second the seroma underestimates the tumor bed defined by implanted 
clips. 
Uncertainty in localising the tumor bed in medial or lateral tumors can be overcome by 
increasing the posterior field borders of whole breast tangents, but only at expense of 
increased morbidity of ribcage and lung, and potential mortality in women with left sided 
tumors. The heart is the most sensitive organ, a few Gy being associated with risk of heart 
disease and every effort needs to be made to exclude the organ from treatment volume. 
When localising the tumor bed boost, increasing the clinical target volume is a crude way of 
avoiding geographical miss. This is particularly important in the era of oncoplastic surgery 
when the tumor bed may be well away from its primary location. 
 
Accurate delineation of the target volume is of utmost importance while delivering tumour 
bed boost with external beam radiotherapy. Different institutions use different methods for 
delineation of the tumour bed.  
Clinical history and patients’ recollection of tumour position, clinical photographs, tattoos, 
surgical scar, mammography, surgical clips, ultrasonography, Computerized tomography 

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(CT) scan and Magnetic resonance imaging (MRI) are the commonly utilized techniques. 
Many a times, a combination of one or more of these techniques is considered while 
delineating the tumour bed boost.  
Amongst all the randomised trials assessing role of radiotherapy boost, surgical clips were 
used in all patients for assessing boost volume only in the Budapest trial8. In other studies, 
the boost volumes were usually defined on clinical and surgical details. It was hypothesized 
that increasing differences between local failure rates in whole breast radiotherapy (WBRT) 
arm versus WBRT+boost arm in Lyon trial (4.5% vs. 3.6%), EORTC trial (10.2% vs. 6.2%)  and 
Budapest trial (15.5% vs. 6.7%) [ may well have been due to the different techniques of 
tumour bed delineation as the difference in boost doses between all these trials were not 
significantly different. Hence an accurate delineation of tumour bed is important as it may 
translate into improved local control rates.  
Tumor bed localisation and open or closed cavity BCS:With superficial closure, only the 
superficial aspect of the cavity is closed, allowing the formation of a seroma to prevent 
deformation ofthe breast. A full-thickness closure consists of repositioning of the 
surrounding breast tissue and suturing the deep and superficial layers, preventing the 
development of significant seroma. There is a paucity of data on the influence of surgical 
closure techniques on EB treatment planning. It can be hypothesized that superficial closure 
may lead to a better-delineated cavity as a well-visualized seroma has been shown to 
decrease interobserver variations nevertheless, it may also lead to a larger treatment 
volume and greater late toxicity effects. However, with full-thickness closure, the surgical 
clips may be displaced with the approximation of the surrounding breast tissue and not 
correlate with the true extend of the cavity. In a recently published single institutional 
experience,Shaikh et al.9 did not find statistically significant difference in mean cavity 
visualization scoring (CVS) (Smitt et al10., 1 = no visible cavity, 2–4 = heterogeneous cavity 
with indistinct, distinct, or clearly defined margins, 5 = homogenous cavity with clearly 
defined margins ) or normal tissue dosimetricendpointsbetween 29 patients who 
underwent superficial closure and sixteen patients who underwent full-thickness closure. A 
higher percentage of patients who underwent superficial closure had CVS scores >2 (79% vs. 
63%). The small patient numbers in each cohort and its retrospective nature are the 
limitations of the study. 
 
Oncoplastic BCS techniques with parenchymal rearrangement present new challenges to 
the localisation of the tumour bed and therefore delivery of local boost radiotherapy. 
Although use of whole-breast radiation therapy (RT) is straightforward, difficulties in 
localization of the tumor bed for the local RT boost have not been investigated. 
Pezneret al11carried out a retrospective review of 25 patients who received RT after breast 
conservation surgery with oncoplastic reconstruction. It was found that among 11 patients 
with a minimum of 4 surgical clips placed at tumor resection, 8 (73%) had the final tumor 
bed extend beyond the original breast quadrant or be completely relocated into a different 

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region. In 3 (27%) cases, the clinical treatment volume was 2 to 3 separated regions within 
the breast. 
Thus, in breast cancer patients who have undergone oncoplastic surgery, the tumor bed is 
frequently more extensive and possibly more relocated compared to original 
presentation.Placement of surgical clips after tumor resection and before oncoplastic 
reconstruction may be the most accurate method to localize the RT local boost field12, 13. 
Techniques of Radiotherapy boost delivery-Various techniques of tumor bed boost delivery 
have been extensively studied and their efficacy compared retrospectively and 
prospectively. The various techniques are electrons, photons(less commonly used due to 
higher penetration and increased doses to critical underlying structures) and 
interstitialbrachytherapy (i.e. interstitial placement of needles into tumor bed either 
intraoperatively or postoperatively) 
With most of the centres now having linear accelerators, coronal en face electron beams 
have now become standard practice in most institutions. Minimal dose to underlying normal 
structures, i.e. lung and breast to the maximum, varying energy of electrons, feasibility of 
defining field on skin, an outpatient procedure with minimal patient discomfort make it a 
favourable option for both the patient as well as treating radiation oncologist. Most 
commonly used energies are 9-12 MeV. However, the boost fields defined on the basis of 
clinical details have been found to be erroneous in several studies. Hence, the dimensions as 
well as depth for tumour bed boost should be determined either by fluoroscopy or CT 
combined with surgical clips, or an ultrasound. The most common prescription isodose for 
electron boost delivery is 90-95% isodose. But, in an organ such as breast with multiple 
edges and curvatures in different axes, the prescription isodose may not cover the whole 
target volume uniformly. This problem is commonly seen when tumours are located at areas 
where there is a sudden change in the depths like inframammary and axillary folds. The 
depths of soft tissue vary greatly in these areas and uniform energy electron beam may 
either underdose the tumour bed, or deliver higher dose to underlying normal structures. 
The electrons have limited role in patients with large breasts, tumours situated at a depth 
i.e. closer to heart (on left) and lungs and in folds. CT based planning in three dimensions 
may help to determine the dose distributions accurately and help in choosing the optimal 
energy. 
The margins to be given to tumour bed for defining boost field have also been discussed. 
Harrington et al14 have shown that a boost field marked on the basis of clinical data and 
background with a margin of 2 cm all around covers radiological field with same margin in 
only 1/3rd (33%) of patients. Although Vicini et al. showed that a margin of 1 cm around the 
tumour covers microscopic disease adequately, in EORTC trial margins of 1.5 cm were given 
for microscopically completely excised tumours. Overall, a margin of 1.5-2 cm to the tumour 
bed has been reported to cover all subclinical disease in patients with clear microscopic 
margins. 
Some institutions have practised tumour bed boost by 4-6 MV photons. The practice of 
delivering boost by photons has declined after widespread availability of electrons due to 

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higher penetration and increased doses to underlying critical structures. Photons can be 
used in patients with small tumour bed as late term sequelae of electrons such as 
telangiectasia may not be acceptable to some patients treated with electrons. 
 
Aims and Objectives:Primary objective- To evaluate dosimetric outcomes in tumor bed 
boost irradiation in patients undergoing breast conservative surgery using three different 
surgical techniques 
Secondary objective-Evaluation of cosmesis in patients prior to radiotherapy, at the time of 
completion of radiotherapy and 6 months post completion of radiotherapy 
Material and methods- 
Patients will be screened for the study at the time of radiotherapy simulation for External 
beam radiotherapy 
The sample size has not been calculated as this is a pilot study.Twenty patients will be 
accrued for the purpose of this study. The patients will be divided into three groups: 
Group A- Patients who underwent open cavity BCS 
Group B- Patients who underwent closed cavity BCS 
Group C- Patients who underwent oncoplasty 
Inclusion Criteria- All patients undergoing Breast Conservative Surgery (Open Cavity/Closed 
Cavity) or Oncoplasty will be eligible for this study.  
Exclusion Criteria-1.Patients undergoing Neoadjuvant chemotherapy will not be eligible for 
the purpose of this study. 
2.All patients undergoing Modified Radical Mastectomy will not be eligible for the purpose 
of this study 
Informed consent will be taken for all patients at the time of Radiotherapy simulation. All 
patients will first receive external beam Radiotherapy to the whole breast to a dose of 
40Gy/15#/3weeks.The patients will then be planned for boost radiation to the tumor bed to 
a dose of 12.5 Gy/5#.  
The combination of surgical clips with a treatment planning CT scan for the lumpectomy site 
for electron boost and to determine the appropriate energy will be used for tumour bed 
boost delineation 
For the boost planning CT scan a small thermocol wedge will be used, with a pillow under 
the shoulder to make the surface as flat as possible. 
The pT size in HPR of lumpectomy plus a margin of 2 cm in all directions is the approximate 
size of the boost field. The margins of this field are marked on the skin with the centre of 
scar as the center of the field and copper wire is placed on the markings. 

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5 mm slice thickness CT scan will be taken in the treatment position. After the scan 
acquisition the data will be transferred to the Varian Eclipse treatment planning system. 
The post-operative cavity depicted on the CT images will be contoured section by section. 
All available images will be assigned a cavity visualisation score9 (CVS) as per the British 
Columbia Cancer Agency Cavity visualisation score 0-No visible seroma, 1-scar/shadow, 2-
seroma identifiable but with significant (>30%) uncertainties, 3-seroma identifiable with 
minor (<30%) uncertainties, 4- seroma easily identifiable, generally homogenous with some 
blurring of margin, 5-seroma clearly identifiable, homogenous with sharp boundaries. The 
mean cavity visualisation score will be determined for each group of patients.  
The CTV will be generated by using a 15 mm uniform expansion from the lumpectomy cavity 
but limited by skin and chest wall. The CTV will be extended by an additional 10 mm uniform 
expansion to generate the PTV 
Treatment plans for tumor bed boost irradiation will be made using both electrons and 
photons with 3DCRT technique for each patient and comparison will be made for various 
dosimetric variables. The photon beam plan will only be generated for purposes of 
dosimetric study and will not be used for treatment of the patients 
 The following dosimetric variables will be determined for each patient -seroma cavity 
volume (ccs).  PTV volume (ccs).In addition the ratio between the PTV volumes to the whole 
breast volume will be determined. The Radiation Conformity Index (RCI) will be determined 
for both set of plans. It was first defined by Knoos et al and a revised definition appeared in 
ICRU 62 It is the ratio of volume of the PTV to the volume that receives 95% prescribed dose 
or higher (RCI= V PTV/ V 95%). The Dose Homogeneity Index (DHI) will be determined for 
both set of plans (DHI). It is ratio of dose received by 95% of PTV volume to the dose 
received by 5% of PTV volume (DHI= D≥95%(within PTV) / D≥5% (within PTV) ).  The dose received by 
several normal structures will be determined for both set of plans-normal ipsilateral breast 
tissue (Whole breast volume- PTV volume), contralateral breast, ipsilateral lung, 
contralateral lung and heart 
The borders of the portal will be modified based on the position of the lumpectomy 
cavity/seroma of the scan and marked on the patient. The boost irradiation for all patients 
will be done using electrons. The energy of electrons required will be decided from the 
depth of the lumpectomy cavity. 
In addition the cosmesis will be determined for all the patients prior to starting 
radiotherapy, at the time of conclusion of radiotherapy and 6 months post completion of 
radiotherapy. This will be done by using the criteria suggested by Harris et al 

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1. Excellent: the treated breast almost identical to the 
untreated one. 
2. Good: the treated breast slightly different from the 
untreated breast. 
3. Fair: obvious difference between the two sides without 
major distortion. 
4. Poor: the treated breast is seriously distorted. 
 
 
 
Statistical analysis shall be performed with the Statistical Package for Social Sciences (SPSS, 
Chicago, IL) software package, version 21.0, for Windows A two-tailed PValue less than 0.05 
will be considered as statistical significance in this study.Descriptive statistics, including 
frequency distributions, means± SD, and 95% conﬁdence intervals, to be calculated for 
demographic and treatment variables.The statistical analysis will be carried out using the 
One way ANOVA or Krsukal Wallis test and categorical comparison will be done using Chi 
Square test. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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