Medical Dosimetry
Volume 36, Issue 1 , Pages 28-34, Spring 2011

Conformal Locoregional Breast Irradiation with an Oblique Parasternal Photon Field Technique

Department of Radiation Oncology, University Hospital Gasthuisberg, Leuven, Belgium

Received 10 April 2009; accepted 26 October 2009. published online 25 January 2010.

Article Outline

Abstract 

We evaluated an isocentric technique for conformal irradiation of the breast, internal mammary, and medial supra-clavicular lymph nodes (IM-MS LN) using the oblique parasternal photon (OPP) technique. For 20 breast cancer patients, the OPP technique was compared with a conventional mixed-beam technique (2D) and a conformal partly wide tangential (PWT) technique, using dose-volume histogram analysis and normal tissue complication probabilities (NTCPs). The 3D techniques resulted in a better target coverage and homogeneity than did the 2D technique. The homogeneity index for the IM-MS PTV increased from 0.57 for 2D to 0.90 for PWT and 0.91 for OPP (both p < 0.001). The OPP technique was able to reduce the volume of heart receiving more than 30 Gy (V30), the cardiac NTCP, and the volume of contralateral breast receiving 5 Gy (V5) compared with the PWT plans (all p < 0.05). There is no significant difference in mean lung dose or lung NTCP between both 3D techniques. Compared with the PWT technique, the volume of lung receiving more than 20 Gy (V20) was increased with the OPP technique, whereas the volume of lung receiving more than 40 Gy (V40) was decreased (both p < 0.05). Compared with the PWT technique, the OPP technique can reduce doses to the contralateral breast and heart at the expense of an increased lung V20.

Key Words: Breast cancer, Internal mammary nodes, Radiotherapy, Treatment technique

 

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Introduction 

Postoperative locoregional radiotherapy improves local control and overall survival in node-positive breast cancer patients.1 The complex target volume in locoregional irradiation for breast cancer, in close proximity to the heart and the lungs, renders treatment planning difficult, because different fields have to be aligned to cover the whole target. The dose distribution near the junction area is often inhomogeneous, both at the skin surface and in depth, which can lead to recurrences or complications. A variety of treatment techniques for breast and internal mammary and medial supraclavicular lymph node (IM-MS LN) radiotherapy has been proposed, indicating the absence of a generally accepted technique.2

A widely used technique for irradiation of the breast and the IM-MS LN, in the era before computed tomography (CT)−based treatment planning, combines the tangential breast fields with an anterior mixed photon and electron beam, covering the IM-MS LN. The position of the fields is mostly based on surface anatomy and the dose is prescribed to a point.3 It has been shown that the whole target volume is not always covered with this technique.4 This is partly due to the lack of consensus regarding the target volume definition in locoregional breast cancer, and partly because of large interpatient variability in position of the different target volumes. Currently, guidelines for target volume delineation are available and several studies support the use of CT-based treatment planning in locoregional breast irradiation.4, 5, 6, 7 When a mixed photon and electron beam technique is planned, based on full CT data, matchline problems are highlighted. Adjacent fields can be designed to overlap, to abut, or to allow a small gap to optimise the target coverage. However, even with adequate patient immobilization, there is no guarantee that the overlap or gap can be reproduced consistently.

The subclavicular matchline problems can be solved readily by using half beams for the tangential fields and the supraclavicular field. Modern linear accelerators enable this with asymmetric collimation.8 The alignment between the tangential fields and the parasternal field is a bigger challenge. In the partly wide tangential (PWT) technique, the use of a parasternal matchline is avoided by including the IM LN in the tangential fields.9 This technique was advocated in several comparative planning studies as the most appropriate solution for conformal irradiation of the breast and IM LN.5, 10, 11, 12 A disadvantage to this technique is the contralateral breast dose.

To minimize matchline problems and avoid irradiating the contralateral breast, the oblique parasternal photon (OPP) technique is developed. This mono-isocentric technique uses 4 asymmetric photon fields, sharing 2 matchlines, i.e., the subclavicular matchline and the parasternal matchline.

In this dosimetric study, the OPP technique is compared with a conventional mixed-beam technique: the standard technique in the EORTC 22922 trial3 and a conformal PWT technique.

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Methods and Materials 

Patient selection and simulation protocol 

A retrospective study was performed on 20 breast cancer patients (10 left- and 10 right-sided), requiring radiotherapy to the breast and the IM-MS LN.

All patients underwent classical simulation. Patients were positioned on a breast board with 10° inclination and both arms stretched above the head. A fixed SSD technique was used for all fields of the conventional plan. An anterior field was determined to cover the IM-MS LN. The field edges were consistent with the requirements of EORTC protocol 22922.3

A CT scan in treatment position was subsequently performed.

Definition of target volumes and critical structures 

Target volumes and organs at risk (OARs) were delineated on the transverse CT slices. The clinical target volume (CTV) consisted of the breast and the ipsilateral IM-MS LN. The contouring of the breast was based on the lead wire placed around the palpable breast tissue during simulation. Delineation of the IM-MS LN was based on published guidelines.7 The planning target volume (PTV) was generated by expanding the breast and IM-MS CTV by 1 cm and 0.5 cm, respectively. The breast PTV was defined to start 5 mm beneath the skin. The following OARs were outlined: both lungs, which are considered one organ; the heart; the contralateral breast; and the esophagus.

Treatment planning 

The dose prescribed to the target volumes was 50 Gy, delivered in 2 Gy fractions. Full 3D dose distributions are calculated using the pencil beam algorithm for photons and a Monte Carlo based algorithm for electrons, both implemented in Eclipse (Varian Medical Systems, Inc., Palo Alto, CA). Three field setups are generated for each patient:

Conventional irradiation technique (2D) (Fig. 1A) 

The field edges were determined during conventional simulation. An anterior field was used to cover the IM-MS LN. For the first 13 fractions, irradiation was performed using photons, and for the remaining 12 fractions electrons were used. The photon dose was prescribed at 3cm depth, measured along the beam axis. The electron energy was chosen in such a way that the 85% isodose encompasses the prescription point that determines the depth of the IM-MS PTV at a slice 3 cm cranial to the central axis slice. Two symmetric, wedged, tangential photon fields were used to irradiate the breast PTV. The breast and parasternal fields were matched on the skin, without overlap.

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  • Fig. 1. 

    Field setup and dose distribution of the irradiation techniques compared in this study: (A) conventional mixed beam technique, (B) partly wide tangential technique, and (C) oblique parasternal photon technique. PTV = planning target volume; IMN = internal mammary lymph nodes; MED = medial tangential field; LAT = lateral tangential field; ANT ε/φ = anterior parasternal electron and photon fields; OP/φ = oblique parasternal photon field.

Conformal irradiation techniques 


a. Partly wide tangential technique (Fig. 1B): Three asymmetrically collimated fields with the same isocenter were created. Wide tangential, wedged, quarter beams included the breast and IM PTV. The MS PTV was irradiated by an anterior half-beam, slightly angled to avoid complete irradiation of the esophagus. To localize the isocenter, first a point was set at the dorsal edge of the tangential fields at midseparation on the central-axis plane. This point was then moved cranially to a plane through the clavicular head at the level where the IM-MS LN move from their caudal, more superficial, to their cranial, deeper location.

b. Oblique parasternal photon technique (Fig. 1C): Four asymmetrically collimated fields were created following an isocentric technique, similar to the one described earlier, regarding the location of the isocenter and the MS field. A medial and a lateral tangential wedged quarter-beam included the breast PTV, and a separate parasternal quarter-beam, with the same gantry angle as the medial tangential field, covers the IM PTV.

For both conformal plans, multileaf collimator shielding was used and all fields were planned using 6- or 10-MV photon beams. The treatment plan was normalized at a reference point, located at the center of the breast PTV. The plans were developed to deliver 95% of the prescribed dose to the breast PTV and 85% of the prescribed dose to the IM-MS PTV.

Evaluation of the dose distributions 

Dose-volume histogram (DVH) comparison 

For the evaluation of the PTV, the mean dose and the fraction of PTV receiving 85% (IM-MS), 95% (breast), and 105% (IM-MS and breast) of the prescription dose were obtained from the DVH curves. The PTV homogeneity index (HI) was defined as the fraction of the PTV, with a dose between 95% and 105% of the prescription dose for the breast and between 85% and 105% for the IM-MS target. The same upper level (105%) was chosen in the calculation of the HI for the breast and the IM-MS target, because an overlap can occur between both PTVs.

Lung and heart DVH data were analyzed for the volume of each organ receiving 20, 30, and 40 Gy (V20, V30, and V40), as well as for the mean lung and heart doses. For the contralateral breast, the volumes receiving more than 5 and 15 Gy (V5 and V15) were used to compare the treatment techniques.

Radiobiological comparison 

For the lungs and the heart, normal tissue complication probabilities (NTCPs) were calculated, applying the relative seriality model.13 The different levels of homogeneous dose in the lungs and the heart were determined by applying a differential DVH decomposition technique.14 Each dose level was recalculated to 2 Gy-fractions using a biological effective dose model with α/β = 3. Endpoints for NTCP calculation for the lungs and the heart were radiation pneumonitis (D50 = 34, γ = 0.9, s = 0.06)15 and excess of cardiac mortality risk (D50 = 52.3, γ = 1.28, s = 1),16 respectively.

Statistical analysis 

To compare the parameters used in the evaluation of the different techniques, the paired t-test was used. All tests were two-tailed, and differences were considered statistically significant when the p-value was ≤0.05 for the comparison of 2 techniques and ≤0.025 for the comparison of 3 techniques (with Bonferroni adjustment for multiple testing).

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Results 

Target volumes 

In Fig. 2, the mean cumulative DVHs of the breast PTV and IM-MS PTV are shown for all 3 treatment techniques. Both 3D techniques (PWT and OPP) show improved target coverage, compared with the 2D technique, and certainly compared with the IM-MS target.

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  • Fig. 2. 

    Mean cumulative DVHs with standard deviation (--) for breast PTV (A) and IM-MS PTV (B), comparing 2D, PWT, and OPP plans. PTV = planning target volume; IM-MS = internal mammary and medial supraclavicular lymph nodes; 2D = conventional mixed beam; PWT = partly wide tangential; OPP = oblique parasternal photon.

Table 1 lists the dosimetric parameters for the target volumes, averaged over 20 patients. The differences between 2D and 3D techniques were statistically significant (p < 0.025) for both the mean dose and the HIs of the breast PTV and IM-MS PTV. The 3D plans showed a comparable coverage and homogeneity for both PTVs.

Table 1. Dosimetric data (means ± SD) for the target structures
TargetParameter2DPWTOPP
Breast PTVMean dose (Gy)48.1⁎±2.249.4±0.649.5±0.7
V47.5 (95%) (%)82.4±10.886.4±5.786.3±6.3
V52.5 (105%) (%)10.7±10.45.0±5.25.9±7.5
HI0.7⁎±0.10.8±0.10.8±0.1
IM-MS PTVMean dose (Gy)43.4⁎±4.446.3±1.046.2±1.2
V42.5 (85%) (%)64.3⁎±2590.6±5.191.3±3.6
V52.5 (105%) (%)9.2⁎±11.91.0±2.20.3±0.6
HI0.6⁎±0.20.90±0.040.91±0.03

Abbreviations: IM-MS = internal mammary and medial supra-clavicular nodes; 2D = conventional mixed beam technique; PWT = partly wide tangential technique; OPP = oblique parasternal photon technique; HI = homogeneity index.

⁎Significantly different from PWT and OPP technique (p < 0.025, two-sided paired t-test).

Critical structures 

Because the conventional 2D treatment technique yielded insufficient target coverage, mainly for the IM-MS nodes, this technique was not considered suitable for further comparison. Both conformal treatment techniques had similar target coverage and their ability to spare the OARs can thus be compared.

Lungs 

The mean cumulative lung DVHs showed consistent differences between OPP and PWT (Fig. 3): larger lung volumes were exposed to low doses with the OPP technique and to higher doses with the PWT technique. The crossover point was at 33.1 Gy. The mean lung dose (MLD), V20, V30, V40, and NTCP values for each technique are shown in Table 2. There was no significant difference in MLD or NTCP values between both techniques. The V20 was significantly higher with the OPP technique, whereas the V40 was significantly higher with the PWT technique (both p < 0.05).

Table 2. Dosimetric data (means ± SD) for the critical structures
Critical StructureParameterPWTOPP
LungMean dose (Gy)8.8±1.29.1±1.2
V20 (%)18.5⁎±2.820.5±3.2
V30 (%)15.8±2.616.5±2.7
V40 (%)10.0±2.27.4⁎±1.5
NTCP (%)1.31.3
Heart†Mean dose (Gy)6.3±3.35.2⁎±2.8
V20 (%)9.7±7.77.8±6.9
V30 (%)7.1±6.75.2⁎±5.2
V40 (%)4.1±5.01.3⁎±2.0
NTCP (%)10.6⁎
Contralateral breastV5 (%)4.4±8.00.7⁎±1.2
V15 (%)2.4±4.80.3⁎±0.6

Abbreviations: PWT = partly wide tangential technique; OPP = oblique parasternalphoton technique; NTCP = normal tissue complication probability.

⁎Statistical significant difference (p < 0.05, two-sided paired t-test).

†Only left-sided patients are considered in the comparison.

Heart 

The mean cumulative heart DVHs of both techniques for the left-sided patients are shown in Fig. 4. It is clearly seen that less heart was irradiated with the OPP technique. The mean heart dose (MHD), V20, V30, V40, and NTCP values for the left-sided patients are shown in Table 2. Significant differences occurred between both techniques in MHD, V30, V40, and NTCP values, in favor of the OPP technique (all p < 0.05).

Contralateral breast 

The percentage of irradiated volume of the contralateral breast is presented in Table 2. Significantly higher values were found for the V5 and V15 with the PWT technique (both p < 0.05).

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Discussion 

Target coverage 

Conventional versus conformal irradiation techniques 

The 2D plan did not cover the target volumes adequately; primarily, the coverage of the IM-MS target was not satisfactory. The reason for this is twofold. First, dose prescription for the IM-MS electron field at a slice 3 cm cranial to the central axis slice, and for the IM-MS photon beam at 3cm depth on the beam axis, was not adequate and resulted in under-dosage to the MS part. This was caused by the deeper location of the lymph nodes cranially. Arthur et al.5 reported the change in IM-MS LN target depth within an individual patient and pointed at the importance of customizing the location of the matchline between the supraclavicular and the tangential fields, which is only possible when full CT data are available.

Second, the use of standard fields, with edges based on surface anatomy, lacks accuracy given the large variability in the location of the IM-MS LN. Bentel et al.6 showed that radiation field edges, based on surface anatomy had to be shifted in 65% of patients when CT information was available. In a previous study,17 we showed that in more than half of the patients the medial edge of the standard anterior IM-MS field (located 1 cm across the midline) needed to be shifted to the lateral side when CT-based target delineation was taken into account. Most of the time this is not feasible when breast tangential fields have to match the anterior IM-MS field, because a cold triangle (region of underdosage that can occur between the anterior IM-MS field and the tangential breast fields) will then be located in the breast CTV. Therefore, not only field edges and dose prescription, but also the field set-up, should be adapted to the CT-based target localization and patient anatomy.

PWT versus OPP. 

Both techniques yielded a comparable homogeneity and target coverage. With either technique, the breast PTV or IM-MS PTV is not completely covered by, respectively, the 95% and 85% isodoses, because a compromise is often made not to include the full PTV margin to reduce normal tissue dose.

OAR sparing: 3D techniques: PWT versus OPP 

Lung 

In the current study, a constraint of V20 <25 % was used for both lungs. Literature data and retrospective DVH analyses of the former conventional 2D treatment technique used in this institute led us to expect a very low complication rate with this constraint.18 Both the PWT and OPP techniques enabled meeting this constraint for all patients. However, the V20 of the lungs was significantly larger with the OPP technique compared with the PWT technique. This is because of the less shallow beam arrangement of the tangential fields with the OPP technique, sparing the contralateral breast. Up to now, 50 patients with a follow up of more than 6 months were treated with the OPP technique in this department. No radiation pneumonitis requiring steroids was detected (data not shown).

Heart 

Compared with the conventional technique that uses an anterior field to irradiate the IM LN, both 3D techniques in this study use oblique beams to treat the IM LN. Hurkmans et al.4 showed that the dose to the heart can be reduced by using an oblique parasternal field instead of an anterior beam. Although the doses to the heart can be minimized by choosing oblique incident fields, in some patients with an “unfavourable” cardiac anatomy (no separation between the anterior heart border and the chest wall) a considerable part of the heart can still be in the field. This explains the large range of cardiac V30 values (0.3−22.4 for PWT and 0.1−16 for OPP) among the left-sided breast cancer patients in this study. An arbitrary value of 10% as a threshold for the cardiac V30 is applied in this study. This constraint could be reached in all but 1 patient with the OPP technique and in all but 3 patients with the PWT technique. In all patients, heart doses were reduced with the OPP technique. This is important in view of the growing use of medication as anthracyclines and trastuzumab in breast cancer treatment that can amplify the cardiotoxic risk.

NTCP models 

Because a combination of parameters (V20, V30, V40, MLD, and MHD) need to be extracted from the DVHs to compare dose distributions, it might be more accurate to use NTCP models based on complete DVH curves. However, the predictive models are not validated with clinical data from a current patient population treated with modern techniques and should be used for relative comparison only. In the current study, similar NTCP values for radiation pneumonitis were found for both competing techniques. The average NTCP for late cardiac mortality was significantly better for the OPP technique.

Contralateral breast 

A disadvantage of the PWT technique is the higher dose to the contralateral breast. A more shallow arrangement of the tangential fields in the PWT plan is a probable cause. Minimizing this dose is important to reduce the risk of secondary cancer induction. In addition, high doses to the medial part of the contralateral breast make future tangential irradiation of the contralateral breast technically problematic. This is relevant because the incidence of contralateral breast cancer is about 5% (varying from 2−11% in different studies).19

Techniques for IM LN irradiation in the literature 

The PWT technique was advocated in several comparative planning studies as the most appropriate balance of target coverage and normal tissue sparing.5, 10, 11, 12 However, these studies have some drawbacks because they did not make optimal use of 3D planning, shielding was not similar for all techniques, and margins around the IM CTV were not appropriate. Pierce et al.11 compared 7 techniques, including the PWT technique and a technique with a mixed beam oblique parasternal field (30/70 P/E). The cardiac NTCP for the PWT technique was lower than in our study (0.05% vs. 1%) because of the use of a heart block. When the IM LN volume and the heart overlapped, preference was given to shield the heart, blocking a portion of the IM LN volume and the inferior breast or chest wall. The inferior part of the breast or chest wall was then treated using supplemental electrons. On the other hand, the cardiac NTCP values of the (30/70 P/E) technique were higher than the values of our OPP technique, although no electrons were used (1.74% vs. 0.6%). Neither CT planning nor heart shielding was used for this technique. In a study by Severin et al.,12 the PWT technique compared favorably with an oblique electron technique. In 6 of 16 patients, the depth of the superior IM LN was >6 cm, resulting in inadequate coverage of the IM LN, although high electron energies were chosen (20−22 MeV) or a low-weighted photon field was associated.

An interesting study by van der Laan et al.20 used CT planning for all competing techniques. They compared the PWT technique with a parasternal mixed-beam technique (anterior electron field and oblique photon field to treat the IM LN). Patients with IM LN exceeding a depth of 5 cm were excluded because the adequate use of electrons would be precluded in these patients, essentially biasing the study. They considered the parasternal mixed-beam technique to be the most optimal. The dose to the lungs and heart can indeed be reduced by using a mixed-beam parasternal field, with part of the fractions given with an oblique or anterior electron field instead of a photon-only parasternal field. However, this solution was not considered in our study, for several reasons. First, the benefit of using one isocenter would have been lost and matchline problems would have occurred along the parasternal and supra-clavicular matchline.20, 21 Second, the use of electrons is not adequate if the depth of the target volume is more than 5 cm and this was the case in about half of our patients (data not shown). Third, an oblique electron beam delivers a high skin dose, possibly leading to prominent skin telangiectasia. Finally, treatment planning and delivery is more complex and time consuming, which is relevant, taking into account the high breast cancer patient load.

The dosimetric advantages of IMRT for the treatment of locoregional breast cancer have been evaluated in several planning studies. The proposed IMRT techniques consist in one method of tangential beams with segmentation,21 and in another with multiple beams, covering an arc of 180°−360°.22 These planning studies showed good target coverage, accompanied by a reduction of heart and lung doses. However, the downside to IMRT with multiple beams is an increased dose to healthy tissue. Depending on the technique used, increased doses to the contralateral breast, lung, esophagus, thyroid, and humeral head are reported. Furthermore, more monitor units are needed in multibeam IMRT to deliver the desired dose, which gives more leakage radiation and subsequently a higher total-body dose. The carcinogenic risk after IMRT is estimated to be almost doubled compared with conventional 3D treatment.23 This is especially relevant for breast cancer patients because they usually have a long life expectancy. Further investigation should focus on reduction of normal tissue dose before clinical implementation of IMRT in all breast cancer patients. In patients for whom heart and lung constraints cannot be reached using conventional CT-based treatment techniques, it could be beneficial to use IMRT. There is reason to believe that the OPP technique proposed in this paper is not incompatible with the segmentation IMRT technique.

Respiratory gated breast radiotherapy also provides a means of reducing the dose to heart and lung.24, 25 Gating for breast irradiation is most interesting in the inspiration phase because of the reduced lung density and the increased distance between the target and the heart, as the heart moves posterior during inspiration.

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Conclusions 

This study supports the use of CT-based treatment planning for locoregional breast radiotherapy. The conventional treatment plan with standard fields based on surface anatomy and dose prescription to a point did not result in the desired target coverage. The isocentric OPP technique achieved comparable target coverage as the PWT technique and resulted in lower heart doses and in a reduction of the irradiated volume of the contralateral breast. A trade-off to use this technique is the increase in the percentage of the lungs that received more than 20 Gy, although lung NTCP values were equally low for both the PWT and OPP techniques.

The OPP technique is clinically implemented in this department and used as the new standard for locoregional breast irradiation. However, the optimal technique is patient-individual and depends on the patient-specific anatomy. In some patients with laterally implanted breasts or the internal mammary lymph nodes located completely behind the breast, the PWT technique can be a better choice. Obese patients and those with an unfavourable cardiac anatomy are difficult to treat with either technique. Those patients may benefit from more complicated treatments like IMRT or respiratory gating.

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Acknowledgments 

This work was partially supported by grants from the Myny-Vanderpoorten Foundation and Varian Medical Systems.

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References 

  1. Clarke M, Collins R, Darby S, et al. Effects of radiotherapy and of differences in the extent of surgery for early breast cancer on local recurrence and 15-year survival: An overview of the randomised trials. Lancet. 2005;366:2087–2106
  2. Erven K, Van Limbergen E. Regional lymph node irradiation in breast cancer. Future. Oncol. 2007;3:343–352
  3. Poortmans P, Kouloulias V, van Tienhoven G, et al. Quality assurance in the EORTC randomized trial 22922/10925 investigating the role of irradiation of the internal mammary and medial supraclavicular lymph node chain works. Strahlenther. Onkol. 2006;182:576–582
  4. Hurkmans CW, Saarnak AE, Pieters BR, et al. An improved technique for breast cancer irradiation including the locoregional lymph nodes. Int. J. Radiat. Oncol. Biol. Phys. 2000;47:1421–1429
  5. Arthur DW, Arnfield MR, Warwicke LA, et al. Internal mammary node coverage: An investigation of presently accepted techniques. Int. J. Radiat. Oncol. Biol. Phys. 2000;48:139–146
  6. Bentel G, Marks LB, Hardenbergh P, et al. Variability of the location of internal mammary vessels and glandular breast tissue in breast cancer patients undergoing routine CT-based treatment planning. Int. J. Radiat. Oncol. Biol. Phys. 1999;44:1017–1025
  7. Dijkema IM, Hofman P, Raaijmakers CP, et al. Loco-regional conformal radiotherapy of the breast: Delineation of the regional lymph node clinical target volumes in treatment position. Radiother. Oncol. 2004;71:287–295
  8. Klein EE, Taylor M, Michaletz-Lorenz M, et al. A mono isocentric technique for breast and regional nodal therapy using dual asymmetric jaws. Int. J. Radiat. Oncol. Biol. Phys. 1994;28:753–760
  9. Marks LB, Hebert ME, Bentel G, et al. To treat or not to treat the internal mammary nodes: A possible compromise. Int. J. Radiat. Oncol. Biol. Phys. 1994;29:903–909
  10. Dogan MH, Zincircioglu SB, Zorlu F. Comparison of various radiation therapy techniques in breast cancer where target volume includes mammaria interna region. Med. Dosim. 2009;34:42–50
  11. Pierce LJ, Butler JB, Martel MK, et al. Postmastectomy radiotherapy of the chest wall: Dosimetric comparison of common techniques. Int. J. Radiat. Oncol. Biol. Phys. 2002;52:1220–1230
  12. Severin D, Connors S, Thompson H, et al. Breast radiotherapy with inclusion of internal mammary nodes: A comparison of techniques with three-dimensional planning. Int. J. Radiat. Oncol. Biol. Phys. 2003;55:633–644
  13. Gagliardi G, Bjöhle J, Lax I, et al. Radiation pneumonitis after breast cancer irradiation: Analysis of the complication probability using the relative seriality model. Int. J. Radiat. Oncol. Biol. Phys. 2000;46:373–381
  14. Van den Heuvel F. Decomposition analysis of differential dose volume histograms. Med. Phys. 2006;33:297–307
  15. Seppenwoolde Y, Lebesque JV, de Jaeger K, et al. Comparing different NTCP models that predict the incidence of radiation pneumonitis (Normal tissue complication probability). Int. J. Radiat. Oncol. Biol. Phys. 2003;55:724–735
  16. Gagliardi G, Lax I, Soderstrom S, et al. Prediction of excess risk of long-term cardiac mortality after radiotherapy of stage I breast cancer. Radiother. Oncol. 1998;46:63–71
  17. Weltens C, Erven K, Petillion S, et al. Impact of CT-based target delineation on the location of the internal mammary and median supraclavicular field [abstract]. Eur. J. Cancer. 2007;5(suppl):2065
  18. Graham MV, Purdy JA, Emami B, et al. Clinical dose-volume histogram analysis for pneumonitis after 3D treatment for non-small cell lung cancer (NSCLC). Int. J. Radiat. Oncol. Biol. Phys. 1999;45:323–329
  19. Chen Y, Thompson W, Semenciw R, et al. Epidemiology of contralateral breast cancer. Cancer. Epidemiol. Biomarkers. Prev. 1999;8:855–861
  20. van der Laan HP, Dolsma WV, van 't Veld AA, et al. Comparison of normal tissue dose with three-dimensional conformal techniques for breast cancer irradiation including the internal mammary nodes. Int. J. Radiat. Oncol. Biol. Phys. 2005;63:1522–1530
  21. Cho BC, Hurkmans CW, Damen EM, et al. Intensity modulated versus non-intensity modulated radiotherapy in the treatment of the left breast and upper internal mammary lymph node chain: A comparative planning study. Radiother. Oncol. 2002;62:127–136
  22. Dogan N, Cuttino L, Lloyd R, et al. Optimized dose coverage of regional lymph nodes in breast cancer: The role of intensity-modulated radiotherapy. Int. J. Radiat. Oncol. Biol. Phys. 2007;68:1238–1250
  23. Hall EJ. Intensity-modulated radiation therapy, protons, and the risk of second cancers. Int. J. Radiat. Oncol. Biol. Phys. 2006;65:1–7
  24. Korreman SS, Pedersen AN, Nottrup TJ, et al. Breathing adapted radiotherapy for breast cancer: Comparison of free breathing gating with the breath-hold technique. Radiother. Oncol. 2005;76:311–318
  25. Remouchamps VM, Vicini FA, Sharpe MB, et al. Significant reductions in heart and lung doses using deep inspiration breath hold with active breathing control and intensity-modulated radiation therapy for patients treated with locoregional breast irradiation. Int. J. Radiat. Oncol. Biol. Phys. 2003;55:392–406

PII: S0958-3947(09)00125-3

doi:10.1016/j.meddos.2009.10.006

Medical Dosimetry
Volume 36, Issue 1 , Pages 28-34, Spring 2011

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