Dosimetric Characteristics of IMRT Versus 3DCRT for Intact Breast Irradiation With Simultaneous Integrated Boost

221

AbstrAct

Background and Purpose: Whole breast irradiation is part of breast conservative management for early breast cancer. Simultaneous Integrated Boost methods are used for head & Neck and Prostate cancers. Most recently SIB for intact breast is gaining interest. In this study we attempt to compare and analyze the dosimetric aspects of Simultaneous Integrated Boost technique (SIB) of IMRT over 3DCRT.

Methods: We took the CT simulation data of 27 consecutive patients for our retrospective study to compare the SIB-IMRT and SIB-3DCRT. Dose prescribed was 45 Gy/25 fractions to whole breast (1.8 Gy/Fraction) and 60 Gy/25fractions to Lumpectomy cavity (2.4Gy/Fraction) .The prescribed dose delivered in a 5 fraction per week schedule. Treatment Plans were compared for Target Minimum, Maximum, Mean, Conformity Index, Homogeneity Index and Organs at Risk doses were compared and analysed.

Results: The Target coverage was achieved with 95% of prescription to the 95% of the lumpectomy cavity as well as whole breast for all the plans. Dose conformity to the boost volume was significantly higher with IMRT technique; 3DCRT technique showed more dose spillage outside the boost volume. SIB-IMRT better in sparing critical organs parameters like Lung V20 &Mean, Heart V30&Mean, and LAD maximum dose.

Conclusion: We infer from our study that both methods achieved adequate target coverage, IMRT reduces maximum doses and improves Conformity and Homogeneity indices of target volumes, also reduces dose to OAR.

Dosimetric Characteristics of IMRT versus 3DCRT for Intact Breast Irradiation with

Simultaneous Integrated Boost1Suresh Moorthy, M.Sc, M.Phil, 2Prof. P. Narayana Murthy, Ph.D,

1Dr. Saroj Kumar Das Majumdar, MD, DNB, 1Dr. Hamdy El Hateer, MD, 3Dr. R. Mohan, Ph.D, 1V. Ramanathan, B.Sc.

1Division of Radiation Oncology, Department of Oncology & Hematology, Salmaniya Medical Complex, MOH, Manama, Kingdom of Bahrain.

2Acharya Nagarjuna University, Nagarjuna Nagar, Guntur, AP, India.3American Hospital, Dubai, UAE.

Author's address for communication: Mr. Suresh Moorthy, Division of Radiation Oncology, Department of Oncology & Hematology, Salmaniya Medical Complex, MOH, Manama, Kingdom of Bahrain.E-mail: [email protected]

Keywords: Simultaneous Integrated Boost (SIB), Intensity Modulated Radiotherapy (IMRT), Three Dimensional Conformal Therapy (3DCRT), Left Anterior Descending Artery (LAD)

222Austral - Asian Journal of Cancer ISSN-0972-2556, Vol. 11, No. 3, July 2012

IntroductIon

breast cancer is the most common cancer in female worldwide. As per WHo estimate, in bahrain the incidence of breast cancer was 116.47 per 100,000in 2008. radiotherapy is an integral part of breast cancer management after breast conservative surgery (bcs). survival rates are similar for bcs with adjuvant rt and mastectomy for early stage breast cancer. Whole breast irradiation is the commonest method of management for early breast cancer treatment after bcs. there are various methods to employ radiotherapy for breast cancer in women. conventionally tangential fields are employed to treat the whole breast. With the recent advances in treatment planning technology and Multi Leaf collimators (MLc), three dimensional conformal radiotherapy (3dcrt) is widely used for treatment of breast carcinoma. conformal therapy reduces normal tissue doses and increases conformity to target volume.

Introduction of Intensity Modulated radiotherapy (IMrt) to breast cancer treatment further improved conformity and doses to normal tissue. switch over from 3dcrt to IMrt for whole breast irradiation, may result in improved PtV coverage and oAr spare but this assumption needs more clinical assessment. studies have shown improved homogeneity of PtV coverage with the use of IMrt over 3dcrt, the median volume of PtV receiving >110% of prescribed dose was 0.1% with IMrt compared to 10 % with conventional wedges.1

several studies in breast cancer have indicated that delivering a boost dose to the tumor bed plus margin, typically with electrons, following conventional whole breast radiotherapy results in improved in-breast control rates.2 Local recurrence after boost radiation to the tumor bed was 6.2 % compared to 10.2% without boost so it became standard of care for early stage breast cancer.3

the conventional dose fractionation schedule for whole breast irradiation is 50 Gy in 25 fraction over 5 week duration, when boost is given it takes 2-3- more weeks making over all treatment period 7-8 weeks, shortening of over all treatment period would be more convenient for patients (especially those coming from remote areas to rt facilities) and for health care providers, as it would increase the turnover in rt departments.

sIb method delivers 45 Gy to whole breast and 60 Gy to surgical cavity in 25 fractions simultaneously by prescribing the dose per fraction 1.8 Gy to whole breast and 2.4 Gy to boost volume. so the total treatment duration reduces by 2 weeks. the radiobiology asserts

that shorter the course of treatment better tumor control probability. A study in early breast cancer patients by donovan E et al showed that IMrt had better cosmetic results compared to conventional treatment.4 recently sIb for breast is gathering momentum. We were using the sIb-IMrt for whole breast for the past two years. In the present study we attempt to compare the sIb planning and dosimetric criteria of 3dcrt and IMrt.

MAtErIALs And MEtHods

We took ct simulation data of 27 consecutive patients (13 left sides and 14 right sides) for our retrospective planning study. these patients were already treated by sIb-IMrt. radiation therapy was started within 3 weeks after all surgery and chemotherapy. the same ct data sets, target volumes and organ at risk volumes were used for sIb-3dcrt study. breast size varied from 985.5 cm3 to 3692.1 cm3with a mean of 1602.3 cm3. tumor bed volume varied from 33.4 cm3 to 420.8 cm3 with a mean of 119 cm3.

target delineation

After Planning ct scan is done, the dIcoM images were transferred to Eclipse version 10.0.34 (Varian Medical systems, usA) treatment planning system. then Planning target Volume (PtV) and organ at risk Volumes (oAr) were delineated. the rtoG breast cancer atlas was used as guideline for target delineation. the clinical target Volume (ctV-1) is the whole breast and supraclavicular and axillary lymph nodes were included as per indication, ctV-2 is lumpectomy cavity and the surgical clips. the PtV-1 was created using three dimensional margin of 5mm around ctV-1 except anteriorly towards the skin was decreased to zero and posteriorly towards the lung was increased to 7 mm. the PtV-2 is created with an outer margin of 5mm to 1 cm from ctV-2.the organ at risk (oAr) structures are delineated according to clinical and radiological data in the ct-Images taken on breath hold. the oAr are contoured as Lungs, contra lateral breast, Heart, LAd (Left Anterior descending Artery), spinal cord, Esophagus, trachea, humerus head and Liver.

Planning details and dose prescription

6 MV X-ray from clinac 600cd Linear Accelerator (Varian Medical systems, usA) which integrated with 120 leaves Millennium MLc was used for dynamic

Suresh Moorthy

pp 221-230


IMrt treatment. the dynamic MLc leaf width is from the central 20cm of field has 5mm leaf width and outer 20cm of field has 10mm leaf width.

the treatment fields are almost evenly spaced within an arc of 180 degree on the side of the tumour. Gantry angles ranged from 330 to150 (clockwise) for left side tumours and from 50 to 210 (counterclockwise) for right side tumours. the dose prescribed to the breast volume (PtV-1) was 45 Gy in 25 fractions (1.8Gy/fraction) and boost volume (PtV-2) was 60 Gy in 25 fractions (2.4 Gy/fraction) in 5 fractions per week schedule. the target dose uniformity and conformity are calculated and evaluated.

the conformity index (cI) as defined in Icru 83 is cI (ref) = Volume of PtV covered by the reference dose / Volume of PtVcI = 1.0 is ideal valuethe Homogeneity Index (HI) as defined in Icru isHI = d 2% - d 98% / d 50%HI = 0 (Zero) is ideal value Where d 2%, d 98%, d 50% is dose received by 2%, 98%, 50% volume

3dcrt planning

using beams Eye View (bEV) fields were set up to minimize the dose to heart and lung and maximize the

target coverage. two plans were created for 3dcrt. In plan 1, two to four coplanar beams were used to produce adequate dose coverage for whole breast volume (PtV-1) and two coplanar beams were used for tumor bed volume (PtV-2). critical organs were shielded using MLc without compromising PtV coverage. beam weights were adjusted until the optimum coverage and acceptable hot spots were achieved. In addition to that the field in fields was created to reduce hotspot or better target coverage and to improve homogenous dose distribution in PtV-1 and PtV-2. Whole breast set to receive at least 95% of the prescribed breast dose. similarly, 95 % of the boost volume set to receive at least 95 % of the boost dose. then integrated treatment plan comprising Whole breast plan and boost plan were generated with common isocenter.

IMrt Planning

new volume is created by the name Whole breast excluding boost volume by subtracting boost volume with 5mm margin from whole breast volume. seven coplanar beams were used to achieve the minimum criteria of 95% of the volume receives the 95% of the prescribed dose. the dose constraints to the target and critical organs were mentioned in Table 1. Heterogeneity correction was done using Modified batho method in Eclipse. dose-Volume Histograms (dVH) was used to analyze the Volume receiving 20Gy, 30Gy and 40Gy, Mean, Maximum and Minimum doses. Also to illustrate the low

Table 1: Optimization objectives for Simultaneous Integrated Boost IMRT plans

Organ Type Target (Gy) Volume (%)

PtV1-PtV2 MAX 47 0

(Whole breast excluding tumor bed) MIn 45 100

PtV2 MAX 62 0

(tumor bed only) MI n 60 100

Ipsilateral Lung MAX 20 30

MIn 10 35

Heart MAX 36 0

MIn 30 20

LAd MAX 30 0

Dosimetric Characteristics of IMRT versus 3DCRT for Intact Breast .....

pp 221-230


dose volume effect, V5Gy volume and Integral dose (Id) were calculated for normal healthy tissue.

Integral dose (Id) = Mean dose (Gy) X Volume (cm3)

statistical Analysis

statistical Analysis was performed using the Wilcoxon signed rank test. this matched pair t test was applied to determine the statistical difference between the dose –volume data for IMrt versus 3dcrt. the reported p value is two tailed and p values of < 0.05 are considered significant.

rEsuLts

the planning objectives are met in all cases with both the techniques. 3dcrt plans frequently shown hotspots near the skin surface but within the acceptable range. the normalized target coverage of IMrt and 3dcrt and their breast PtV and boost PtV are presented in Table 2a, 2b.the dose distribution in axial sections is shown in Figures 1a, 1b.these axial sections clearly shows that concave PtV coverage and exclusion of LAd during optimization by IMrt.

there is a consistent improvement in cI for breast volume from 0.233 for 3dcrt to 0.201 for IMrt (p=0.04311) also for boost volume from 0.1061 for 3dcrt to 0.0834 for IMrt (p=0.0128).the HI is improved with IMrt for the breast volume (p=0.0012) and to lesser extent for the boost volume (p= 0.1126). to evaluate the better conformity, V50 Gy and V55 Gy volumes were created in whole breast excluding boost volume and significant dose spillage outside the boost volume is recorded.

Ipsilateral lung V20 Gy is significantly reduced with IMrt (p< 0.0001). both lungs V20 Gy is significantly improvement with IMrt (p<0.0001). the oAr results are represented in the table 3.

In our study the heart V30 Gy is 2.71% for IMrt than 3.94 % for 3dcrt. the V40 Gy is significantly lower in IMrt than 3dcrt (p= 0.05), the LAd maximum dose is 41.22 Gy for 3dcrt and 29.16 Gy for IMrt (p=0.0046). to evaluate low dose volume effect V5 Gy is calculated and dose paint shown in Figure 2. dose Volume Histograms (dVH) describing the dose volume relationship of the target as well as normal tissues of the both techniques is presented in Figure 3a-3g. dVH shows better normal tissue sparing with IMrt than 3dcrt.

Table 2a: Comparison of Whole breast minus boost volume coverage parameter (Mean) for IMRT and 3DCRT methods of whole breast cancer patients (Prescribed Dose 45 Gy)

Dosimteric Parameter SIB-3DCRT SIB-IMRT P Value

Minimum dose (Gy) 24.07 32.03 0.0016

Maximum dose (Gy) 60.03 59.68 0.0002

coverage (%) 96.8 98.22 0.0012

conformity Index 0.233 0.201 0.04311

Homogeneity Index 1.033 1.018 0.0012

Mean dose (Gy) 49.72 51.62 <0.0001

Modal dose (Gy) 49.12 48.92 ns

Median dose (Gy) 50.5 48.8 0.0071

standard deviation(Gy) 6.35 4.17 <0.0001

V 50 Gy (%) 48.69 29.83 <0.0001

V 55 Gy (%) 30.7 11.29 <0.0001

Suresh Moorthy

pp 221-230


Table 2b: Comparison of boost volume coverage parameter (Mean) for IMRT and 3DCRT methods of whole breast cancer patients (Prescribed Dose 60 Gy)

Dosimteric Parameter SIB-3DCRT SIB-IMRT P Value

Minimum dose (Gy) 53.96 55.25 0.0061

Maximum dose (Gy) 65.79 64.18 0.0009

coverage (%) 97.3 99.38 ns

conformity Index 0.1061 0.0834 0.0128

Homogeneity Index 1.037 1.006 ns

Mean dose (Gy) 61.24 61.65 ns

Modal dose (Gy) 61.12 62.39 0.0027

Median dose (Gy) 61.18 62.0 0.0089

standard deviation(Gy) 1.7 1.31 0.0119

Fig1b: represents the axial section dose distribution of sIb-IMrt in which capable to exclude LAd in order to cover the concave target.

Fig1a: represents the axial section dose distribution of sIb-3dcrt in which LAd receives high dose

Table 3: Comparison of Mean values of Normal tissue dose volume parameters for IMRT and 3DCRT breast cancer patients

Parameter SIB-3DCRT SIB-IMRT P Value

Ipsilateral Lung

V20 Gy (%) 39.355 26.827 <0.0001

V30 Gy (%) 32.244 16.081 <0.0001

Mean (Gy) 20.294 16.51 0.0006

Max (Gy) 60.48 53.68 <0.0001


pp 221-230


Fig 3a: represents a cumulative dose Volume Histogram (dVH) of breast PtV comparing sIb methods of 3dcrt and IMrt plans.

Fig 3 b: represents a cumulative dose Volume Histogram (dVH) of boost PtV comparing sIb methods of 3dcrt and IMrt plans.

Fig 2: represents the 5Gy volume of dose color wash of 3dcrt and IMrt

Heart

V30 Gy (%) 3.936 2.71 ns

V40 Gy (%) 2.08 0.753 0.05

Mean (Gy) 7.44 7.08 ns

Both Lung

V20 Gy (%) 19.997 13.615 <0.0001

Mean (Gy) 11.52 10.82 0.0001

Contralateral Breast

V5 Gy (%) 6.12 5.65 ns

LAD

Maximum dose (Gy) 41.22 29.16 0.0046

Suresh Moorthy

pp 221-230


Fig 3 d: represents a cumulative dose Volume Histogram (dVH) of both Lung comparing sIb methods of 3dcrt and IMrt plans

Fig 3 f: represents a cumulative dose Volume Histogram (dVH) of Heart comparing sIb methods of 3dcrt and IMrt plans

Fig 3 c: represents a cumulative dose Volume Histogram (dVH) of Ipsilateral Lung comparing sIb methods of 3dcrt and IMrt plans

Fig 3 e: represents a cumulative dose Volume Histogram (dVH) of contralateral breast comparing sIb methods of 3dcrt and IMrt plans

Fig 3 g: represents a cumulative dose Volume Histogram (dVH) of normal Healthy tissue comparing sIb methods of 3dcrt and IMrt plans

dIscussIons

In our institution, we are using 60 Gy in 25 fractions for whole breast and tumor bed irradiation using sIb technique based on the bEd calculation as presented in the Table 4. the calculated bEd values are comparable to conventional fractionation schedules.

In general, both IMrt and 3dcrt provided similar results regarding PtV coverage. but in depth analysis of dosimteric data revealed significant differences in quality of target coverage and normal tissue doses. In this study we used equally spaced beam angles for IMrt and tangential fields for 3dcrt plans. the use of equally spaced gantry angles improved homogeneity and conformity indices,


pp 221-230


also reduced the volume of oAr such as the heart and ipsilateral lung receiving a high dose as shown by Hong et al.5 though the mean breast volume is 1602cc which is relatively higher with respect to literature that showed the mean breast volume of 483 cc, we were able to have optimized coverage and reduced dose to oAr.6 bct long term complication is generally acceptable but using higher dose per fraction for the sIb technique needs further reduction of dose to critical structure.

IMrt for breast is explored for its ability to confirm the dose to the concave target volume. With increasing sophistication in radiation treatment plans, Homogeneity indices showed improvement with inverse IMrt as reported by Fisher.7 compared to conventional tangential field breast radiotherapy, conformal rt proved better normal tissue sparing, IMrt proved further reduction of skin toxicity and late effects so the quality of life improved much. the potential advantages that IMrt technique may have over conventional 3d and non-3d techniques are (1) the ability to achieve dose uniformity throughout the breast target and (2) the potential to reduce the dose to underlying heart and lung. these abilities are expected to translate into an improved cosmetic outcome and reduced toxicity.

the inverse-planned IMrt further reduce hotspots, because of beam modulation during optimization compared to 3dcrt. reports from Planning studies with multiple fields show that PtV95% coverage values ranging from 90% to 99 % whereas all our optimized plans had PtV95% coverage values of >95% of prescription dose.8, 9 the incidence of radiation Pneumonitis (rP) is related to the ipsilateral lung volume irradiated.10 In our study the Ipsilateral Lung V20 for IMrt (26.83%) is significantly less than (39.36%) 3dcrt (P<0.0001). both Lung V20 Gy and Mean dose is also significantly lower in IMrt than 3dcrt (p<0.0001).contra lateral

lung V5 Gy and mean dose of both the methods show no significant differences.

the ipsilateral MLd was 16.51 Gy for IMrt, compared to 20.29 Gy in 3dcrt plan (p=0.0006). the mean lung doses are higher compared to the report from Marks L b et al as 6.4 to 11 Gy probably because of larger breast volumes. there is no absolute safe Mean Lung dose (MLd) below which there is no pneumonitis.11 the clinically acceptable risk of rP depends on the risk-benefit ratio of the individual patient selection basis.

In patients with breast cancer, it is intended that the irradiated heart volume be minimized to the greatest possible degree without compromising the target coverage. the risk of pericardial events is probably related to both dose and volume of radiation. stewart Jr et al concluded that the dose should be limited to 60 Gy for less than 25% of cardiac volume and 45 Gy for more than 65% of cardiac volume.12 Gagliardi et al reported that cAd risk was much reduced at doses less than 30 Gy.13 In our study the mean values of V30 Gy were 2.7% and 3.9% for IMrt and 3dcrt respectively compared to studies reporting V30 Gy values in the range of 2% to 5%.14 Increased cardiac mortality risk associated with Left side breast patients in the long term was reported by multiple relatively old literatures.15, 16 the advances in the treatment techniques including IMrt reduced cardiac exposure so that steady decline of radiation risk is being noticed.17 boivin et al noted that the anteriorly placed coronary arteries were more often affected by rt (compared with the circumflex artery).18 In our study LAd maximum dose (mean) is 41.22 Gy for 3dcrt and 29.16 Gy for IMrt (p=0.0046) Mean heart doses for Lt. breast patients were 4 Gy for IMrt and 6.5 Gy for 3dcrt, this results are comparable to other studies.

the IMrt plans contributed a modestly higher dose

Table 4: Comparison of BED for SIB versus conventional fractionation schedules

α/β 50 Gy/25 #+16Gy/8#Sequential Boost

60Gy /25#SIB

Late responding tissue (3Gy)

110 Gy 104 Gy

breast cancer (4Gy) 99 Gy 96 Gy

Early responding tissue(10 Gy)

79 Gy 74.4 Gy

Suresh Moorthy

pp 221-230


to adjacent healthy soft tissues. Especially the low dose volume (V5 Gy) which represents the late effects was higher in IMrt. the excess dose to normal tissue outside the whole breast volume is created. In our study the mean V5 Gy volume for conformal therapy is significantly lower than IMrt. the main concern with healthy soft tissue dose increases of this magnitude is an increased risk of late second malignancy.19, 20

the monitor unit for IMrt is 6-8 times more than 3dcrt is a concern.21 this shows that the integral dose would also be higher. Pirzkall et al studied that the Integral dose for IMrt is higher than conventional treatment.22 the Integral dose (Id) in our work for IMrt significantly higher than 3dcrt. the Id is higher probably due to multiple beams used in IMrt than tangential oriented 3d conformal so that large volume of healthy tissue involved during optimization, this in turn increases treatment time during delivery. Also the leakage and scatter dose to non target tissue is proportional to the number of monitor units used. some studies reported, increased low dose volumes with increased number of beam angles.23 the Integral dose data were represented in Table 5.

High integral dose attributed to second malignancy which is likely to be of greatest concern in younger women and in patients with a low risk for systemic relapse that are likely to live for many years after the diagnosis of breast cancer.24 there have been reports that adjuvant rt for breast cancer may increase the risk of lung cancer and angiosarcoma.25 the risk of sarcoma in the treated volume is likely to be similar with IMrt or standard techniques, but it is possible that second primary lung cancers might be increased by IMrt, especially in smokers. 24 balancing the short to medium-term benefits of reducing the volume of heart and left lung receiving a high dose of rt against the risk of late malignancy requires an individual assessment of the treatment volume goals and the patient’s longevity prospects with and without rt. Evaluation of 121 patients treated with IMrt compensation found a 3% rate of secondary malignancy after 7 years26 which was not

significantly differ from 4% rate observed by conventional radiation.27 Limited studies are available for breast with sIb IMrt. the dosimteric study investigated by various authors with advanced techniques in selected cases, IMrt is definitely beneficial compared to conformal therapy.28, 29 Many authors quoted that sIb with IMrt is feasible and proved better compared to sequential method of treatment.30-32

concLusIon

We infer from our study that both methods proved better in target coverage but IMrt reduces maximum doses and improves conformity and Homogeneity indices of target volumes. Also dose to oAr like ipsilateral lung, Heart, LAd is higher with conformal rt. simultaneous Integrated boost method with 3dcrt and IMrt for breast cancer treatment is feasible.

rEFErEncEs

1. Kestin LL, sharpe Mb, Frazier rc, Vicini FA, Yan d, Matter rc, et al. Intensity modulation to improve dose uniformity with tangential breast radiotherapy: initial clinical experience. Int J radiat oncol biol Phys 2000; 48:1559 -1568.

2. Arthur d W, Morris MM ,Vicini FA, dogan n , breast IMrt , In: bortfeld t ,schmidt –ullrich r , de neve W , et al editor .Image guided IMrt, Germany:springer-Verlag berlin Heidelberg; 2006;pp.371-381 .

3. collette s, collette L, budiharto t, Horiot Jc, Poortmans PM, struikmans H, et al. Eortc radiation oncology Group: Predictors of the risk of fibrosis at 10 years after breast conserving therapy for early breast cancer: a study based on the Eortc trial 22881-10882 ‘boost versus no boost’. Eur J cancer 2008; 44:2587-2599.

4. donovan E, bleakley n, denholm E, Evans P, Gothard L, Hanson J, et al. breast technology Group: randomised trial of standard 2d radiotherapy (rt) versus intensity modulated radiotherapy in patients prescribed breast radiotherapy. radiother oncol 2007; 82:254-264.

5. Hong L, Hunt M, chui c, spirou s, Forster K, Lee H, et al. Intensity modulated tangential beam irradiation of the intact breast. Int J radiat oncol biol Phys 1999; 44:1155-64.

6. Hijal t, Fournier-bidoz n, castro-Pena P, Kirova Y M, Zefkili

Table 5: Comparison of MU, ID and V5 parameter (Mean) for IMRT and 3DCRT chest wall breast cancer patients

Parameter SIB-3DCRT SIB-IMRT P Value

Monitor units 281 1530 <0.0001

Integral dose (Gy-cm3)105 1.34 1.9 0.01

V5 Gy (%) 18.898 30.612 0.0004


pp 221-230


s, bollet M A, et al. simultaneous integrated boost in breast conserving treatment of breast cancer: a dosimetric comparison of helical tomotherapy and three-dimensional conformal radiotherapy. radiother oncol 2010; 94: 300-306.

7. Fisher J, scott c, stevens r,Marconi b, champion L , Freedman GM, et al. randomized phase III study comparing best supportive care to biafine as a prophylactic agent for radiation induced skin toxicity for women undergoing breast irradiation: radiation therapy oncology Group (rtoG) 97-13. Int J radiat oncol biol Phys 2000; 48: 1307–1310.

8. chui cs, Hong L, Hunt M, Mccormick. A simplified intensity modulated radiation therapy technique for the breast. Med Phys2002; 29:522–529.

9. donovan EM, bleackley nJ, Evans PM, reise sF, Yarnold Jr , et al. dose-position and dose-volume histogram analysis of standard wedged and intensity modulated treatments in breast radiotherapy.br J radiol2002; 75:967–973.

10. recht A, Ancukiewicz M, Alm El-din MA, Lu XQ, Martin c, berman sM, et al. Lung dose-volume parameters and the risk of pneumonitis for patients treated with accelerated partial-breast irradiation using three-dimensional conformal radiotherapy. J clin oncol 2009; 27:3887-389.

11. Marks Lb, bentzen sM, deasy Jo, Kong FM, bradley Jd, Vogelius Is, et al. radiation dose-volume effects in the lung. Int. J. radiat oncol biol.Phys 2010; 76:s70-7.

12. stewart Jr, GajardoLF, Gillette sM, constine Ls. radiation injury to the heart. Int. J. radiat oncol biol.Phys 1995; 31(5):1205-1212.

13. Gagliardi G, constine Ls, Moiseenko V, correa c, Pierce LJ, Allen AM,et al. radiation dose-volume effects in the heart. Int. J. radiat oncol biol.Phys 2010; 76:s77-85.

14. rongsriyam K, rojpornpradit P, Lertbutsayanukul c, sanghangthum t, oonsiri s. dosimetric study of inverse-planed intensity modulated, forward-planned intensity modulated and conventional tangential techniques in breast conserving radiotherapy. J Med Assoc thai 2008; 91:1571–1582.

15. ragaz J, olivotto IA, spinelli JJ, Phillips n, Jackson sM, Wilson Ks, et al. Locoregional radiation therapy in patients with high-risk breast cancer receiving adjuvant chemotherapy: 20-Year results of the british columbia randomized trial. J natl cancer Inst 2005; 97:116–126.

16. Høst H, brennhovd I, Loeb M. Postoperative radiotherapy in breast cancer - long term results from the oslo study. Int J radiat oncol biol Phys 1986; 12:727–732.

17. Giordano sH, Kuo YF, Freeman JL, buchholz tA, Hortobagyi Gn, Goodwin Js, et al. risk of cardiac death after adjuvant radiotherapy for breast cancer. J natl cancer Inst 2005; 97:419–424.

18. boivin JF, Hutchison Gb, Lubin JH, Mauch P. coronary artery disease mortality in patients treated for Hodgkin’s disease. cancer1992; 69:1241–1247.

19. Kirova YM, de rycke Y, Gambotti L, Pierga JY, Asselain b, Fourquet

A. second malignancies after breast cancer: the impact of different treatment modalities. br J cancer2008; 98:870–874.

20. Gao X, Fisher sG, Emami b. risk of second primary cancer in the contralateral breast in women treated for early-stage breast cancer: A population-based study. Int J radiat oncol biol.Phys 2003; 56:1038–1045.

21. Jothybasu Ks, bahl A, subramani V, rath GK, sharma dn, Julka PK. static versus dynamic intensity-modulated radiotherapy: Profile of integral dose in carcinoma of the nasopharynx. J Med Phys 2009; 34:66-72.

22. Pirzkall A, carol M, Lohr F, Hoss A, Wannenmacher M , debus J. comparison of intensity-modulated radiotherapy with conventional conformal radiotherapy for complex-shaped tumors. Int J radiat oncol biol.Phys 2000; 48:1371-1380.

23. cho bcJ, schwarz M, Mijnheer bJ, bartelink H. simplified intensity-modulated radiotherapy using pre-defined segments to reduce cardiac complications in left-sided breast cancer. radiother oncol 2004; 70:231–41.

24. Followill d, Geis P, boyer A. Estimates of whole-body dose equivalent produced by beam intensity modulated conformal therapy. Int J radiat oncol biol.Phys 1997; 38:667-672.

25. Hall EJ, Wuu cs. radiation-induced second cancers: the impact of 3d-crt and IMrt. Int J radiat oncol biol Phys 2003; 56:83–88.

26. Mcdonald MW, Godette Kd, Whitaker dJ, davis LW, Johnstone PA. three-year outcomes of breast intensity-modulated radiation therapy with simultaneous integrated boost. Int J radiat oncol biol Phys 2010; 77: 523-530.

27. Mcdonald MW, Godette Kd, butker EK, davis LW, Johnstone PA. Long-term outcomes of IMrt for breast cancer: A single institution cohort analysis. Int J radiat oncol biol Phys 2008; 72:1031–1040.

28. Fogliata A, nicolini G, Alber M, Asell M, dobler b, El-Haddad M,et al: IMrt for breast, a planning study. radiother oncol 2005; 76:300-310.

29. Fogliata A, bolsi A, cozzi L. critical appraisal of treatment techniques based on conventional photon beams, intensity modulated photon beams and proton beams for therapy of intact breast. radiother oncol 2002; 62:137-145.

30. Hurkmans c, Meijer G, van Vliet-Vroegindeweij c, sangen M van der, cassee J. High dose simultaneously integrated breast boost using intensity modulated radiotherapy and inverse optimisation. Int J radiat oncol biol Phys 2006; 66:923-930.

31. singla r, King s, Albuquerque K, creech s, dogan n. simultaneous integrated boost intensity modulated radiation therapy (sIb-IMrt) in the treatment of early stage left sided breast carcinoma. Med dosim 2006; 31:190-196.

32. Laan H van der, dolsma W, Maduro J, Korevaar E, Hollander M, Langendijk J. three.dimensional conformal simultaneously integrated boost technique for breast conserving radiotherapy. Int J radiat oncol biol Phys 2007; 68:1018-1023.

Suresh Moorthy

pp 221-230

Documents

Dosimetric Characteristics of IMRT Versus 3DCRT for Intact Breast Irradiation With Simultaneous Integrated Boost