early experience of tomotherapy-based intensity … · original article early experience of...

Clinical Oncology (2009) 21: 294e301doi:10.1016/j.clon.2009.01.010

Original Article

Early Experience of Tomotherapy-based Intensity-modulatedRadiotherapy for Breast Cancer Treatment

H. O’Donnell*, K. Cookey, N. Walshy, P. N. Plowman*y*Department of Radiotherapy, St Bartholomew’s Hospital, London, UK; yDepartment of Radiotherapy,

The Cromwell Hospital, London, UK

ABSTRACT:Aims: New technology - specifically intensity-modulated radiotherapy (IMRT) - is now being applied to breastradiotherapy and a recent dosimetric analysis confirmed the advantages of IMRT over ‘wedge-only’ plans. Suchapplication to everyday practice raises new issues and here we present the early experience of IMRT-based breastirradiation in a single centre.Materials and Methods: We present cases of breast cancer treated by Tomotherapy�-based IMRT, where the perceivedadvantages of IMRT are considerable. Cases presented are bilateral disease, left breast irradiation, pectus excavatum,prominent contralateral prosthesis and internal mammary chain disease. We discuss the practicalities of such treatmentand the advantages over standard breast irradiation techniques.Results: Advantages include better conformity of treatment with lowering of dosages to underlying organs at risk, forexample ipsilateral lung and heart. There is improved coverage of the planning target volume, including regional nodes,without field junction problems. Planning, quality assurance and treatment delivery are more time consuming than forstandard breast irradiation and the low dose ‘bath’ is increased.Conclusions: The standard radiotherapy tangential technique for breast/chest wall treatments has not significantlychanged over many decades, whereas across many other tumour sites there have been great advances in radiotherapytechnology. The dosimetric advantages of IMRT are readily apparent from our early experience. The wider spread of thelower dose zone (the low dose ‘bath’ of radiation) is a potential concern regarding late oncogenesis and methods tominimise such risks should be considered. O’Donnell, H. et al. (2009). Clinical Oncology 21, 294—301

ª 2009 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Key words: Breast radiotherapy, IMRT, tomotherapy

Introduction

Radiotherapy is an important part of treatment for manybreast cancer patients and it accounts for a substantialproportion of a radiotherapy department’s workload d es-timated at 30e40% of most UK radiotherapy department’sworkload by fractionation. Adjuvant breast radiotherapyleads to improved local control rates over breast-conserv-ing surgery alone [1]. Postoperative radiotherapy has alsobeen shown to be associated with increased survival d therecent appreciation of this 4e5% survival gain being animpetus to optimise locoregional control in this disease;this survival advantage also extends to node-positivepatients after total mastectomy [1]. The survival benefitis independent of systemic therapy and meta-analyses showthat an overall survival benefit is maintained even afterother deaths, unrelated to breast cancer, are taken intoaccount [1]. Studies within the last 10 years have showna survival advantage to node-positive patients receivingregional node radiotherapy in addition to adjuvant chemo-therapy; this has fuelled renewed interest in safe regional

0936-6555/09/210294þ08 $36.00/0 ª 2009 The Royal Col

node radiotherapy, including the internal mammary nodechain [2].

Radiotherapy planning and delivery continue to evolveacross most tumour sites. Standard tangential fieldsencompass the breast/chest wall with or without regionalnodes, whereas three-dimensional conformal radiotherapyenables one to encompass the target volume using fixed,shaped radiation beams of uniform intensity across the fieldor with modification by devices, such as wedges. Whetherassessed clinically or by computed tomography, the extentof glandular breast tissue can be difficult to localise andthere is documented interobserver variability in delinea-tion, most significantly for tumour bed boost radiotherapy[3]. The definition of the target becomes an ever moreimportant issue as the sophistication of conformationaltechnology increases and margins are reduced.

Intensity-modulated radiotherapy (IMRT) uses inverseplanning and optimised non-uniform beam intensities withtreatment plans generated using computer algorithms. Assuch, IMRT techniques are significantly more complex thanthree-dimensional conformal radiotherapy and have the

lege of Radiologists. Published by Elsevier Ltd. All rights reserved.

295TOMOTHERAPY-BASED IMRT FOR BREAST CANCER

potential to achieve superior dose homogeneity and normaltissue sparing, especially for targets and organs at risk (OAR)with complex shapes, such as the breast/chest wall [4].Tomotherapy is computed tomography-guided IMRT thatdelivers radiation helically, allowing precise delivery ofradiation while sparing the surrounding normal tissues. Theradiation source rotates around the patient and is modulatedby rapidly moving micro multileaf collimators, such that theradiation is delivered using multiple tiny beamlets, therebyoffering better conformity than standard LINAC-based IMRT,as illustrated by the cases described here.

The use of helical tomotherapy, with the gantry rotatingaround the patient delivering radiation from any gantryangle, is not optimal for breast irradiation because whencompared with standard tangents, use of all gantry anglesresults in the delivery of low doses to areas in the body thatwould only receive a scatter dose during conventionalradiotherapy. The organs of particular concern being thecontralateral breast and lung. Topotherapy, which is notyet in clinical practice, uses the tomotherapy unit in fixedgantry positions with the beam intensity modulated by themicro collimators as the patient is moved through a station-ary gantry. The breast irradiation technique in use at theCromwell Hospital is a tomotherapy-based IMRT techniquedesigned to limit the low dose bath effect. The OAR areblocked so that beams do not enter through them in orderto irradiate the target, effectively creating a tangentialapproach. This technique uses a more limited number andangle of beams than standard helical tomotherapy.

The introduction of such new techniques for breastradiotherapy raises new issues and here we illustrateexamples from our experience to date with tomotherapy-based IMRT. The cases presented demonstrate clinicalsituations that pose challenges to the clinician, dosimetristand physicist alike. They represent typical problems arisingin the context of breast irradiation and we discuss some ofthe practicalities, advantages and the potential pitfalls ofIMRT-based radiotherapy with reference to these cases. Weinclude examples of bilateral breast radiotherapy, regional

Fig. 1 e Standard tangential radiotherapy treating different chest wall shaconventional tangents (shown in yellow).

node irradiation (supraclavicular fossa and internal mam-mary node chain), radiotherapy after breast implantationand dose volume histogram (DVH) analyses for the OAR.

Patients and Methods

IMRT breast irradiation was carried out on a Hi-ArtTomotherapy� (Wisconsin, USA) apparatus at The CromwellHospital, London. Patients presented here were selected asthey exemplified common difficulties experienced in breastirradiation and show the advantages of IMRT-based irradi-ation. All patients were positioned with both arms up ona MEDTEC wingboard with vacfix to immobilise the elbows.Patients were instructed on gentle breathing during (axial)scanning as per department protocol after performing anin-house study into variation with inhale/exhale techniqueson computed tomography. Each computed tomography dataset took about 1 min to acquire.

Target Definition

The aim of most radiotherapy treatments is to delivera homogenous dose. Most centres have or are moving towardsfull three-dimensional planning for breast irradiation.Patient factors such as breast size, chest wall shape andincline are considered when planning the gantry angles andcollimator rotations. Limiting factors are lung and cardiactissue, as measured at the time of the simulator image, andmedial and lateral borders are often compromised to reducethe extent of normal tissue irradiation. Nevertheless,tangential fields often encompass significant volumes oflung, cardiac and normal soft tissues and the amount ofvariation between patients can be large, as seen in Fig. 1.

With adjuvant breast treatment, the breast tissue plus orminus locoregional lymph nodes is considered the clinicaltarget volume (CTV). This is a biological entity taking intoaccount risk of microscopic disease in the remaining breasttissue and in the draining lymph nodes and will vary

pes showing the variation in the extent of normal tissue included by

296 CLINICAL ONCOLOGY

between patients. The planning target volume (PTV) isa geometric entity, and includes margins added to allow fororgan movement (inter-fraction and intra-fraction) and set-up error. Any potential advantages of three-dimensionalconformal radiotherapy or IMRT will diminish if the targetvolumes are not correctly identified and the precisedelineation of a target volume is critical whether for wholebreast, partial breast or concomitant boost radiotherapy.

We carried out mapping of breast glandular tissue (CTV)as seen on the planning computed tomography scan. Toavoid interobserver variability in contouring, the sameclinician outlined all cases. Glandular tissue was visualisedon computed tomography with the following boundaries:anteriorly, 0.5 cm inside skin, posteriorly, to the chest wallto include clips or deep margins if appropriate, medially,0.5e1 cm to the ipsilateral midline to assist with contra-lateral breast sparing (not possible if medial tumour),laterally, the visualised breast to assist, generally excludingthe axilliary tail. The tumour bed was localised by use ofwire placed over the lumpectomy scar at the planningcomputed tomography and by the appearance of a seromaon computed tomography. Nodal groups (supraclavicularfossa in case 2 and internal mammary node chain in case 4)were outlined by the same clinician on the planningcomputed tomography images.

Intravenous contrast was not used, rather, anatomicallandmarks were used, as per published computed tomog-raphy-based nodal boundaries [5]. A 0.5 cm margin wastypically added to each CTV to give a PTV based ondepartmental calculations of systematic and random

Fig. 2 e Computed tomography in axial plane (left panel) and recoisodosimetry of the bilateral breast radiotherapy plan. The colour code rethe dose volume histogram of the planning target volume and the organ

errors. The PTV remained 0.3 cm from the skin surface toensure some skin sparing. The total time for clinician anddosimetrist outlining for CTV and OAR, respectively, wasabout 2e3 h. Target volumes were treated in 22e25fractions to a dose of 45e50 Gy. In the cases illustrated,the tumour bed was boosted sequentially (8 Gy/4 frac-tions). There were no absolute dose constraints for theheart, lung and contralateral breast. Treatment deliverytime was 8e10 min (beam on) for breast alone, 10e13 minfor breast/chest wall nodes. Verification images were takenfor the first three fractions, and online corrections carriedout. After fraction 3, a correction for systematic set-updeviation was carried out, with images on day 4 with thecorrection. If all parameters were within 0.5 cm tolerance,further imaging was once weekly to minimise concomitantdoses due to image-guided radiotherapy.

Case 1: Bilateral Breast Irradiation

Bilateral breast radiotherapy is challenging with standardradiotherapy techniques, but the use of IMRT can readilyovercome the obvious difficulties while ensuring targetvolume conformity and lung and heart avoidance. It alsoeliminates the problem of overlapping fields. In Fig. 2, theconformity of the therapeutic dose (50 Gy/25 fractions) toboth breasts can be appreciated. The lung doses areexceptionally low, as documented on the correspondingDVH. Inspection of the DVH in Fig. 2 shows that 20% of thecombined lung volume receives !5 Gy and the volume oflung receiving 20 Gy is less than 5%. The axial computed

nstructed coronal computed tomography showing superimposedpresents the total dose to be received (Gy). The lower panel showss at risk.


tomography images show the absence of central overlapdespite bilateral irradiation.

Case 2: Bilateral Breast and LeftSupraclavicular Fossa Irradiation

Irradiation of the supraclavicular fossa nodes is standard forpatients with more than three positive axillary nodes and inthe case presented below, it can be appreciated that thereare obvious advantages of treating such a target volume incontinuity without field junctions. Numerous methods ofirradiating the axilla and supraclavicular fossa are used,such as the single isocentre technique. The side-effects ofradiotherapy in this region can cause significant morbidity,making it essential to minimise excess normal tissueirradiation. In order to encompass the supraclavicular fossawith conventionally planned fields, a significant volume ofnormal tissues, most notably lung, is irradiated. Theincidence of radiation pneumonitis in breast radiotherapyis relatively low, but when attempting to cover regionallymph nodes the risk of lung toxicity increases and thepotential for lung damage increases further still wherebilateral breast radiotherapy is required. Standard radio-therapy techniques, including single isocentre methods, donot overcome the issue of increased lung irradiation andthe possibility of overlapping fields and potential over-dosing of underlying OAR remains. Inclusion of the internalmammary chain nodes in selected cases will further

Fig. 3 e Computed tomography in axial plane (left panel) and recoisodosimetry of the bilateral radiotherapy plan plus unilateral regional nreceived (Gy). The lower panel shows the dose volume histogram of thethe combined lung dose, c.f. that in Fig. 2 is noteworthy, as is the heart aby conventional tangents if standard techniques were used to treat the

increase the extent of normal tissues irradiated by standardmethods, as will be discussed in case 5.

With left-sided breast radiotherapy, as shown in Fig. 3,it can be appreciated that encompassing the target volume(as it curves around the chest wall) with tangents (super-imposed in yellow) would result in significant irradiation ofthe heart, whereas the conformity afforded with IMRTminimises the amount of heart tissue included. The DVHshows that the heart dose for this bilateral case isacceptably low: 20% of the cardiac volume receives just15 Gy, with !3% receiving 30 Gy. The application oftangents, as superimposed in yellow on the images,highlights the contrast in the degree of cardiac irradiationwith conventional radiotherapy. In order to irradiate thetarget volume on the left side, standard tangents wouldencompass a significant volume of the heart and wouldmost probably necessitate compromise of the medial andlateral borders. The figure also shows the synchronous leftregional node irradiation d to a lower dose of 45 Gy (vs50 Gy to the chest wall) with no radiation field gapbetween the nodal and chest wall volumes, only a seamlesstransition. Also noteworthy for a case that encompassesboth breast/chest walls and a unilateral regional nodalvolume (axilla/supraclavicular regions) is that the com-bined lung DVH lies well within acceptable parameters oflung tolerance, although appreciably more than that incase 1 (Fig. 2) where there was no additional nodalradiation.

nstructed coronal computed tomography showing superimposedodal radiotherapy. The colour code represents the total dose to beplanning target volume and the organs at risk d the comparison ofvoidance. The arrowed yellow line shows the volume encompassedleft chest wall.

Fig. 4 e Computed tomography in axial plane (left panel) and reconstructed coronal computed tomography showing superimposedisodosimetry of the right breast radiotherapy plan in a patient with pectus excavatum. The colour code represents the total dose to bereceived (Gy). The lower panel shows the dose volume histogram of the planning target volume and the organs at risk d the combined lungdose is noteworthy, as is the conformity to the chest wall curvature. The arrowed yellow line shows the volume encompassed by conventionaltangents if standard techniques were used to treat the right chest wall.


Case 3: Pectus Excavatum

Anatomical variation between patients necessitating individ-ualisedtherapyiscommonplaceinbreastradiotherapyd mostoften due to variation in breast size and shape and inchest wall curvature. In some instances, the chest wallcurvature poses a particular challenge, such as in thecase of pectus excavatum. This can be appreciatedin Fig. 4, where right breast radiotherapy (45 Gy/22fractions) was delivered to a lady with marked concavityof her anterior chest wall. When a typical tangent isapplied (as shown in yellow) to ensure coverage of thetarget volume, the degree of underlying lung irradiatedwould be considered unacceptable and medial and lateralborders would be altered as a result d potentiallycompromising the target volume coverage. Also noteworthyis the minimal contralateral breast dose d 10% receivingjust 5 Gy and !5% receiving 7.5 Gy.

Case 4: Bilateral Implants and BreastIrradiation

The use of primary reconstructive surgery after breastcancer surgery is becoming increasingly common. Theclinical indications for adjuvant breast radiotherapy remainunchanged, but the practicalities of delivering the radio-therapy are altered. The axial computed tomographyimages in Fig. 5 show the dose (45 Gy/22 fractions)conformity to the right breast treated with IMRT. Fromthe corresponding DVH it is apparent that the contralateral

breast dose is minimal (15% receiving 5 Gy and !5%receiving 7.5 Gy). Given the altered anatomy it can beappreciated that to encompass the target volume withconventional tangents while avoiding the contralateralbreast would not be possible. With IMRT the left breast issuccessfully avoided, as shown in Fig. 5, with no compro-mise on the target volume.

Case 5: Internal Mammary Chain NodalIrradiation

The ability to include the internal mammary lymph nodechain in adjuvant breast radiotherapy without overdosingthe underling structures (notably the heart) is a challengeto which IMRT is tested. Although uncertainty remainsregarding the effectiveness of irradiating the internalmammary nodes, increased interest has been generatedby reports of a survival benefit in selected women whosepostoperative radiation therapy portals often included theinternal mammary chain [2].

OAR, such as the brachial plexus, are difficult to outline,especially on non-contrast planning computed tomographyand cliniciansneed tobecome familiarwith thecross-sectionalanatomy of the thorax. IMRTcan overcome the complexities ofthe target volume and spare dose to the normal tissues. In thecase shown in Fig. 6, the treatment aim was to encompass thebreast, supraclavicular fossa and internal mammary nodechain for adjuvant radiotherapy. As before, the breast dosewas 50 Gy and the locoregional nodes 45 Gy.

Fig. 5 e Computed tomography in axial plane (left panel) and reconstructed coronal computed tomography showing superimposedisodosimetry of right breast radiotherapy after bilateral reconstructive surgery and breast implantation. The colour code represents the totaldose to be received (Gy). The lower panel shows the dose volume histogram of the planning target volume and the organs at risk. The arrowedyellow line shows the volume encompassed by conventional tangents and the degree of contralateral breast irradiation incurred in doing so.

Fig. 6 e Axial computed tomography showing superimposedisodosimetry of left breast radiotherapy and unilateral regionalnodes, including the internal mammary chain irradiation.


Discussion

Conventional radiotherapy techniques for the treatment ofbreast cancer have produced impressive locoregionalcontrol and overall survival rates with little change inmethods over many years. With advances in imaging,treatment planning and delivery we now have newradiotherapy techniques that should offer advantages whilemaintaining the high rates of local control and overallsurvival. IMRT represents one of the most importanttechnological advances in radiotherapy since the adventof the linear accelerator. It is an evolving field showingsignificant potential for improving radiotherapy treatmentfor many patient groups and tomotherapy IMRT is probablythe most sophisticated form of IMRT in clinical practice [6].

The side-effects of breast radiotherapy include lung andcardiac toxicity, lymphoedema, brachial plexopathy, softtissue fibrosis and its cosmetic sequelae, as well as secondmalignancies. Patients accepting adjuvant radiotherapyshould be counselled on the potential benefits of localtreatment along with the side-effects, including latetoxicity, particularly as many patients have a good long-term prognosis d it is with these considerations in mindthat IMRT must be evaluated.

Irradiation of the left breast in particular brings its ownconcerns of cardiac toxicity. Randomised trials and over-views have shown an increased incidence of late cardiacmortality after breast radiotherapy, due largely d it is


accepted d to encompassment of the left ventricle withinthe tangential left breast/chest wall portals. With theincreasing use of anthracyclines and herceptin and theirpotential cardiac toxicities there could be a summationwith radiation, and the relevance of cardiac avoidance,particularly when treating left-sided breast cancers, withradiotherapy has never been greater. In the cases illus-trated here we exemplify the improvements that tomo-therapy IMRT brings in this regard.

The incidence of invasion of the internal mammary chainnodes ranges from 4% in axillary node-negative patients to72% in axillary node-positive patients d the tumourlocation within the breast also being of relevance [2].Since the European Organization for Research and Treat-ment of Cancer (EORTC) trial publication [2], the internalmammary chain may also be included in the desired CTV(after a two to three decade embargo on this practice). OneEORTC study (22922e10925) is currently investigatingwhether elective irradiation of the internal mammary andmedial supraclavicular node chain has a positive impact onsurvival. A common problem noted from the EORTC trialquality assurance data of standard radiotherapy techniquesis the matching of field junctions [2]. Methods of matchingfields vary between institutions and such problems areinevitable with standard radiotherapy, so the benefits ofconformal and IMRT become apparent. With tomotherapy-based IMRT it is possible to treat the breast/chest wall andregional nodes, including the internal mammary nodes, incontinuity, thereby overcoming the issue of overlap or gapsand their resultant sequelae.

Several investigators have described potential advan-tages of IMRT in breast radiotherapy, such as decreasing thedose to the ipsilateral lung and heart, particularly forinternal mammary nodal radiotherapy, and reducing breastreaction and fibrosis through improved dose homogeneity[7e11]. Other studies have looked at the role of IMRT inbreast cancer, addressing differing IMRT techniques, targetdefinition and interobserver variation in outlining, theinclusion of the regional lymph node areas for treatment,and DVH analysis [7,9,10]. Donovan et al. [12] recentlyconfirmed that most of the IMRT treatment planningmethods studied offer advantages over the conventionalwedge pair. However, IMRT does increase the dose to otherorgans not normally considered in conventional breastradiotherapy, such as the contralateral lung, contralateralbreast, thyroid, humoral head and oesophagus. This lowdose ‘bath’ almost exclusively extends only between theupper and lower axial limits of the PTV and the combinedlung DVH graph in Fig. 2 demonstrates well the avoidance ofintermediate dose to OAR, but at the price of a long lowdose ‘tail’ to the curve.

The advantages of improved conformity have to beweighed against the ‘low dose bath’ effect. The increaseddose (albeit low dose) to other surrounding normal tissuesnot previously considered as OAR is a potential disadvan-tage of IMRT for breast irradiation. The significance of lowdose irradiation to these surrounding tissues is as yetunknown. For conventional methods, a small increase inlung and oesophageal cancer incidence has been reported

in a population of patients with overall good long-termsurvival prospects [1]. However, a large-scale, single-institution, retrospective study of 16 705 patients treatedfor non-metastatic breast cancer suggested that standardradiotherapy did not increase the incidence of secondprimary cancers other than sarcomas and lung cancer [13].The subject of late oncogenesis must be studied assidu-ously, with particular reference to IMRT.

The use of IMRT for breast irradiation is not as clear cutas for other tumour sites and the most dramatic improve-ments may only truly be appreciated for the more complextreatments. Accurate target volume localisation by thephysician is fundamental and is undoubtedly more time-consuming for IMRT than clinical localisation by palpablebreast tissue as for the tangential portals’ technique. TheCTV delineated as glandular breast tissue for a conformal/IMRT plan will probably differ from a clinically markedtarget volume and the volume growth CTVePTV. However,target definition apart, the superior dose homogeneity andsparing of OAR with IMRT is apparent.

Planning and quality assurance is more time-consumingfor IMRT, as is daily treatment time for the patient, and thismust be balanced against the advantages discussed above.Conventional tangential radiotherapy is relatively insensi-tive to organ motion and set-up error, but tighter set-uprequirements are necessary for IMRT. During breathing, theIMRT-defined PTV may move outside the external contour(as defined on planning computed tomography) and resultin geographical miss of the target. Methods such asapplication of virtual bolus for planning and dosimetrycalculations can be used to compensate for this [8].Methods used to account for breathing in LINAC-basedbreast radiotherapy include active breathing control andreal-time position management, aiming to deliver treat-ment during phases of the breathing cycle that correspondto those when the planning scan was acquired, e.g. in deepinspiration when the heart is at maximum distance from thechest wall or breast. Image-guided techniques were notused in the cases illustrated here, rather the patients wereinstructed on gentle shallow breathing for planning andtreatment. Future application of IMRT to sites susceptibleto breathing motion, such as the breast, will require furtherconsideration.

In addition to the improvements of IMRT over standardradiotherapy for target coverage, therapeutic homogene-ity, and normal tissue avoidance, IMRT also offers assis-tance in current areas of study, such as partial breastirradiation and the use of concomitant boost radiotherapy.There is as yet no consensus for partial breast radiotherapyor for tumour bed concomitant boost treatment. Clinicaldata have documented that most in-breast failures afterbreast-conserving therapy are in the immediate vicinity ofthe tumour bed [14]. The frequency of these recurrences isgreatly reduced with adjuvant radiotherapy, and thepattern of in-breast failures remote from this site (!5%)is unaltered by radiotherapy [14]. This supports that thebenefit of radiotherapy is at the site of the original lesionand that the risk of new primary disease arising elsewherein the breast is unaltered. As a result, much work is


currently being conducted to investigate the role of partialbreast irradiation, concomitant boost treatment and doseescalation to the tumour bed. Dose-escalated IMRT, givinghigher doses per fraction to high-risk areas, may offera benefit in terms of recurrence risk and also prove to becost-effective. This theory is being examined in the currentIMPORT HIGH and IMPORT LOW phase III clinical trials.Tomotherapy-based IMRT should be well suited to concom-itant boost radiotherapy. However, practitioners of sucha concomitant boost approach must be mindful of possiblecompromise to late cosmetic appearance due to largerfraction sizes. Our experience to date has been with casesin whom late cosmesis was not paramount; in such cases,boosting the originally involved quadrant (with skin sparing)shortened treatment time and has been well tolerated.

The absence of any gaps/junctions between radiationfields when irradiating the chest wall and regional nodes isa perceived advantage of IMRT and we have examples ofpatients in whom there has been heavy axillary involvementin the gap/junction region where this advantage is, webelieve, important.

The potential advantages of IMRT are easy to demon-strate qualitatively in treatment planning exercises, butcareful comparative studies and clinical trials with long-term follow-up are needed to show that IMRT may also offeradvantages not yet fully appreciated. The selected casespresented here exemplify problems in breast radiotherapywhere IMRT is advantageous and we have anecdotallyhighlighted others. Although accepting the argument thatbreast radiotherapy should be made as simple as possible inorder to rationalise departmental resources for thisfrequently employed usage, we believe that the casespresented here demonstrate some of the merits of IMRT.The technique should be further explored while beingmindful of its potential disadvantages.

Author for correspondence: P. N. Plowman, Department ofRadiotherapy, St Bartholomew’s Hospital, 25 Bartholomew Close,West Smithfield, London EC1A 7AE, UK. Tel: þ44-2077200139;E-mail: [email protected]

Received 14 November 2008; received in revised form 5 January2009; accepted 27 January 2009

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