Barbara Dobler

Potential Effect of Robust and Simple IMRT Approach for Left-Sided Breast Cancer on Cardiac Mortality

PURPOSEnThree-dimensional (3D) treatment planning has reduced the cardiac dose in postoperative radiotherapy for breast cancer; however, the overall cardiac toxicity is still an issue because of more aggressive adjuvant treatment. Toxicity models have suggested that a reduction of the heart volume treated to high doses might be particularly advantageous. We compared aperture-based multifield intensity-modulated radiotherapy (IMRT) plans to 3D-planned tangent fields using dose-volume histograms, cardiac toxicity risk, and the robustness to positioning errors.nnnMETHODS AND MATERIALSnFor 14 computed tomography data sets of patients with left-sided breast cancer (unfavorable thoracic geometry), a 3D treatment plan and an IMRT plan were created. The dose-volume histograms were evaluated for the target and risk organs. Excess risk of cardiac mortality was calculated for both approaches using a relative seriality model. Positioning errors were simulated by moving the isocenter.nnnRESULTSnIMRT reduced the maximal dose to the left ventricle by a mean of 30.9% (49.14 vs. 33.97 Gy). The average heart volume exposed to >30 Gy was reduced from 45 cm(3) to 5.84 cm(3). The mean dose to the left ventricle was reduced by an average of 10.7% (10.86 vs. 9.7 Gy), and the mean heart dose increased by an average of 24% (from 6.85 to 8.52 Gy). The model-based reduction of the probability for excess therapy-associated cardiac death risk was from 6.03% for the 3D plans to 0.25% for the IMRT plans.nnnCONCLUSIONnAperture-based IMRT for left-sided breast cancer significantly reduces the maximal dose to the left ventricle, which might translate into reduced cardiac mortality. Biological modeling might aid in deciding to treat with IMRT but has to be validated prospectively.

Frameless stereotactic radiosurgery of a solitary liver metastasis using active breathing control and stereotactic ultrasound.

Background and Purpose:Radiosurgery of liver metastases is effective but a technical challenge due to respiration-induced movement. The authors report on the initial experience of the combination of active breathing control (ABC®) with stereotactic ultrasound (B-mode acquisition and targeting [BAT®]) for frameless radiosurgery.Patients and Methods:A patient with a solitary, inoperable liver metastasis from cholangiocellular carcinoma is presented (Figure 4). ABC® (Figure 3) was used for tumor/liver immobilization. Tumor/liver position was controlled and corrected using ultrasound (BAT®; Figure 1). The tumor was irradiated with a single dose of 24 Gy.Results:Using ABC®, the motion of the tumor was significantly reduced and the overall positioning error was < 5 mm (Figure 2). BAT® allowed a rapid localization of the lesion during breath hold which could be performed without difficulties for 20 s. Overall treatment time was acceptable (30 min).Conclusion:Frameless stereotactic radiotherapy with the combination of ABC® and BAT® allows the delivery of high single doses to targets accessible to ultrasound with high precision comparable to a frame-based approach.Hintergrund und Ziel:Die Radiochirurgie solitärer Lebermetastasen ist effektiv, stellt jedoch aufgrund der Atembewegung des Targets eine technische Herausforderung dar. Die Autoren berichten über die initiale Erfahrung mit der rahmenlosen Radiochirurgie durch die Kombination einer aktiven Atmungskontrolle („active breathing control“ [ABC®]) mit dem stereotaktischen Ultraschall („B-mode acquisition and targeting“ [BAT®]).Patient und Methodik:Präsentiert wird ein Patient mit einer solitären Lebermetastase bei cholangiozellulärem Karzinom (Abbildung 4). ABC® (Abbildung 3) wurde zur Immobilisation des Tumors bzw. der Leber verwendet. Die Position des Tumors bzw. der Leber wurde mit Ultraschall (BAT®) kontrolliert und ggf. korrigiert (Abbildung 1). Der Tumor wurde mit einer Einzeldosis von 24 Gy konformal bestrahlt.Ergebnisse:Durch ABC® konnte die Leber-/Tumorbewegung minimiert werden, die gesamte Positionierungsunsicherheit betrug < 5 mm (Abbildung 2). BAT® erlaubte eine schnelle Lokalisierung des Zielvolumens unter Atemanhalt, was wiederholt über 20 s vom Patienten problemlos ausgeführt wurde. Die Gesamtbehandlungszeit war gegenüber einer ungetriggerten Behandlung kaum verlängert (30 min).Schlussfolgerung:Die rahmenlose Stereotaxie durch Kombination von ABC® und BAT® erlaubt, bei sonographisch zugänglichen Zielvolumina hohe Dosen zu applizieren. Die erreichte Präzision liegt im Bereich jener von rahmenbasierten Verfahren.

Optimization of extracranial stereotactic radiation therapy of small lung lesions using accurate dose calculation algorithms

BackgroundThe aim of this study was to compare and to validate different dose calculation algorithms for the use in radiation therapy of small lung lesions and to optimize the treatment planning using accurate dose calculation algorithms.MethodsA 9-field conformal treatment plan was generated on an inhomogeneous phantom with lung mimics and a soft tissue equivalent insert, mimicking a lung tumor. The dose distribution was calculated with the Pencil Beam and Collapsed Cone algorithms implemented in Masterplan (Nucletron) and the Monte Carlo system XVMC and validated using Gafchromic EBT films. Differences in dose distribution were evaluated. The plans were then optimized by adding segments to the outer shell of the target in order to increase the dose near the interface to the lung.ResultsThe Pencil Beam algorithm overestimated the dose by up to 15% compared to the measurements. Collapsed Cone and Monte Carlo predicted the dose more accurately with a maximum difference of -8% and -3% respectively compared to the film. Plan optimization by adding small segments to the peripheral parts of the target, creating a 2-step fluence modulation, allowed to increase target coverage and homogeneity as compared to the uncorrected 9 field plan.ConclusionThe use of forward 2-step fluence modulation in radiotherapy of small lung lesions allows the improvement of tumor coverage and dose homogeneity as compared to non-modulated treatment plans and may thus help to increase the local tumor control probability. While the Collapsed Cone algorithm is closer to measurements than the Pencil Beam algorithm, both algorithms are limited at tissue/lung interfaces, leaving Monte-Carlo the most accurate algorithm for dose prediction.

Improving Dose Homogeneity in Large Breasts by IMRT

Purpose:Evaluation of a simplified intensity-modulated irradiation (IMRT), a three-field (MFT), and a conventional two-tangential-field technique regarding dose homogeneity, target coverage, feasibility and, for the first time, dosimetric reliability in patients with large breasts treated postoperatively for breast cancer on a low-energy linac.Material and Methods:CT datasets of ten patients with relatively large breast volumes treated for breast cancer were selected. For each patient, four treatment plans were created: low-energy conventional (C-LE), high-energy conventional (C-HE), three-field (MFT), and a two-field aperture-based IMRT technique. Apertures for the IMRT and MFT were created with the aid of a three-dimensional dose display. Dosimetric accuracy of each technique was evaluated in an anthropomorphic thorax/breast phantom.Results:The mean of planning target volumes receiving < 95% or > 105% of the prescribed total dose was reduced from 16.0% to 13.9% to 10.4% to 8.9% in the C-LE, C-HE, MFT, and IMRT plans, respectively. Phantom dose measurements agreed well with the calculated dose within the breast tissue.Conclusion:Aperture-based IMRT using two tangential incident beam directions, as well as a three-field technique with inverse optimization, provide a better alternative to the standard wedged tangential beams for patients with large breasts treated on low-energy linacs while maintaining the efficiency of the treatment-planning and delivery process.Ziel:Evaluation einer einfachen tangentialen intensitätsmodulierten Bestrahlungs-(IMRT-)Technik, einer Drei-Felder-Technik (MFT) und der konventionellen tangentialen Technik im Hinblick auf Dosishomogenität, Erfassung des Zielvolumens, Durchführbarkeit und – erstmalig – dosimetrische Reproduzierbarkeit bei der postoperativen Mammabestrahlung von Patientinnen mit großem Mammavolumen an einem Linac mit niedriger Energie.Material und Methodik:CT-Datensätze von zehn Patientinnen mit relativ großem Mammavolumen, bei denen eine postoperative Radiotherapie wegen Mammakarzinoms durchgeführt worden war, wurden für diese Untersuchung verwendet. Für jede Patientin wurden vier Bestrahlungspläne generiert: Niedrigenergie konventionell (C-LE), Hochenergie konventionell (C-HE), Drei-Felder-Plan (MFT) und eine aperturbasierte Zwei-Felder-IMRT-Technik. Aperturen (Segmente) für die IMRT und MFT wurden mit Hilfe eines dreidimensionalen Dosisdisplays generiert. Die dosimetrische Reproduzierbarkeit der generierten Pläne wurde in einem anthropomorphen Thorax/Mamma-Phantom evaluiert.Ergebnisse:Das mittlere Volumen des Planungszielvolumens, das < 95% oder > 105% der Verschreibungsdosis erhielt, wurde von 16,0% (C-LE) auf 13,9% (C-HE) auf 10,4% (MFT) bzw. 8,9% (IMRT) reduziert. Die gemessene Dosis stimmte für alle Pläne im Bereich der Mamma gut mit der berechneten Dosis überein.Schlussfolgerung:Die aperturbasierte IMRT mit zwei tangentialen Primäreinstrahlrichtungen und die Drei-Felder-Technik mit inverser Optimierung verbessern die Planqualität bei der postoperativen Bestrahlung voluminöser Mammae an Linacs mit niedriger Energie bei hervorragender Behandlungsökonomie.

Intensity-Modulated Radiation Therapy (IMRT)with Different Combinations ofTreatment-Planning Systems and Linacs

Purpose:Purpose: To compare different combinations of intensity-modulated radiation therapy (IMRT) system components with regard tonquality assurance (QA), especially robustness against malfunctions and dosimetry.Material and Methods:Three different treatment-planning systems (TPS), two types of linacs and three multileaf collimatorn(MLC) types were compared: commissioning procedures were performed for the combination of the TPS Corvus® 5.0 (Nomos) andnKonRad® v2.1.3 (Siemens OCS) with the linacs KD2® (Siemens) and Synergy® (Elekta). For PrecisePLAN® 2.03 (Elekta) measurementsnwere performed for Elekta Synergy only. As record and verify (R&V) system Multi-Access v7® (IMPAC) was used. The use ofnthe serial tomotherapy system Peacock® (Nomos) was investigated in combination with the Siemens KD2 linac.Results:In the comparison of calculated to measured dose, problems were encountered for the combination of KonRad andnElekta MLC as well as for the Peacock system. Multi-Access failed to assign the collimator angle correctly for plans with multiplencollimator angles per beam. Communication problems of Multi-Access with both linacs were observed, resulting in incorrect recordingnof the treatment. All reported issues were addressed by the manufacturers.Conclusion:For the commissioning of IMRT systems, the whole chain from the TPS to the linac has to be investigated. Componentsnthat passed the commissioning in another clinical environment can have severe malfunctions when used in a new environment.nTherefore, not only single components but the whole chain from planning to delivery has to be evaluated in commissioningnand checked regularly for QA.Ziel:Ziel: Vergleich verschiedener Kombinationen von IMRT-Systemkomponenten (intensitätsmodulierte Strahlentherapie) hinsichtlichnQualitätssicherung (QA), insbesondere Dosimetrie und Anfälligkeit für Fehlfunktion.Material und Methodik:Es wurden die Kombinationen der Planungssysteme Corvus® 5.0 (Nomos) und KonRad® v2.1.3 (SiemensnOCS) mit den Linacs KD2® (Siemens) und Synergy® (Elekta) sowie des TPS PrecisePLAN® 2.03 (Elekta) mit dem Synergy-Linacn(Elekta) anhand von Standardmethoden der IMRT-QA verglichen. Als R&V-System („record and verify“) wurde Multi-Access v7®n(IMPAC) verwendet. Zusätzlich wurde das Tomotherapiesystem Peacock® (Nomos) für den Einsatz am KD2-Linac (Siemens) überprüft.Ergebnisse:Beim Vergleich von berechneter zu gemessener Dosis zeigte KonRad Probleme in Kombination mit dem Elekta MLCn(Multileaf-Kollimator). Pläne mit mehreren Kollimatorwinkeln pro Feld wurden von Multi-Access mit nur einem Kollimatorwinkelnimportiert. Kommunikationsprobleme zwischen dem R&V-System und den beiden Linacs führten zu einer fehlerhaften Protokollierungnder Bestrahlung. Alle Probleme wurden sofort an die Hersteller gemeldet.Schlussfolgerung:Komponenten, die sich bereits in einer anderen Umgebung bewährt haben, können schwere Mängel aufweisen,nwenn sie in einer neuen Kombination verwendet werden. Daher sollten nicht nur einzelne Komponenten, sondern immer diengesamte Bestrahlungskette kommissioniert und regelmäßig überprüft werden.

Intensity-modulated radiation therapy (IMRT) with different combinations of treatment-planning systems and linacs: issues and how to detect them.

Purpose:Purpose: To compare different combinations of intensity-modulated radiation therapy (IMRT) system components with regard tonquality assurance (QA), especially robustness against malfunctions and dosimetry.Material and Methods:Three different treatment-planning systems (TPS), two types of linacs and three multileaf collimatorn(MLC) types were compared: commissioning procedures were performed for the combination of the TPS Corvus® 5.0 (Nomos) andnKonRad® v2.1.3 (Siemens OCS) with the linacs KD2® (Siemens) and Synergy® (Elekta). For PrecisePLAN® 2.03 (Elekta) measurementsnwere performed for Elekta Synergy only. As record and verify (R&V) system Multi-Access v7® (IMPAC) was used. The use ofnthe serial tomotherapy system Peacock® (Nomos) was investigated in combination with the Siemens KD2 linac.Results:In the comparison of calculated to measured dose, problems were encountered for the combination of KonRad andnElekta MLC as well as for the Peacock system. Multi-Access failed to assign the collimator angle correctly for plans with multiplencollimator angles per beam. Communication problems of Multi-Access with both linacs were observed, resulting in incorrect recordingnof the treatment. All reported issues were addressed by the manufacturers.Conclusion:For the commissioning of IMRT systems, the whole chain from the TPS to the linac has to be investigated. Componentsnthat passed the commissioning in another clinical environment can have severe malfunctions when used in a new environment.nTherefore, not only single components but the whole chain from planning to delivery has to be evaluated in commissioningnand checked regularly for QA.Ziel:Ziel: Vergleich verschiedener Kombinationen von IMRT-Systemkomponenten (intensitätsmodulierte Strahlentherapie) hinsichtlichnQualitätssicherung (QA), insbesondere Dosimetrie und Anfälligkeit für Fehlfunktion.Material und Methodik:Es wurden die Kombinationen der Planungssysteme Corvus® 5.0 (Nomos) und KonRad® v2.1.3 (SiemensnOCS) mit den Linacs KD2® (Siemens) und Synergy® (Elekta) sowie des TPS PrecisePLAN® 2.03 (Elekta) mit dem Synergy-Linacn(Elekta) anhand von Standardmethoden der IMRT-QA verglichen. Als R&V-System („record and verify“) wurde Multi-Access v7®n(IMPAC) verwendet. Zusätzlich wurde das Tomotherapiesystem Peacock® (Nomos) für den Einsatz am KD2-Linac (Siemens) überprüft.Ergebnisse:Beim Vergleich von berechneter zu gemessener Dosis zeigte KonRad Probleme in Kombination mit dem Elekta MLCn(Multileaf-Kollimator). Pläne mit mehreren Kollimatorwinkeln pro Feld wurden von Multi-Access mit nur einem Kollimatorwinkelnimportiert. Kommunikationsprobleme zwischen dem R&V-System und den beiden Linacs führten zu einer fehlerhaften Protokollierungnder Bestrahlung. Alle Probleme wurden sofort an die Hersteller gemeldet.Schlussfolgerung:Komponenten, die sich bereits in einer anderen Umgebung bewährt haben, können schwere Mängel aufweisen,nwenn sie in einer neuen Kombination verwendet werden. Daher sollten nicht nur einzelne Komponenten, sondern immer diengesamte Bestrahlungskette kommissioniert und regelmäßig überprüft werden.

STEREOTACTIC, SINGLE-DOSE IRRADIATION OF LUNG TUMORS: A COMPARISON OF ABSOLUTE DOSE AND DOSE DISTRIBUTION BETWEEN PENCIL BEAM AND MONTE CARLO ALGORITHMS BASED ON ACTUAL PATIENT CT SCANS

PURPOSEnDose calculation based on pencil beam (PB) algorithms has its shortcomings predicting dose in tissue heterogeneities. The aim of this study was to compare dose distributions of clinically applied non-intensity-modulated radiotherapy 15-MV plans for stereotactic body radiotherapy between voxel Monte Carlo (XVMC) calculation and PB calculation for lung lesions.nnnMETHODS AND MATERIALSnTo validate XVMC, one treatment plan was verified in an inhomogeneous thorax phantom with EDR2 film (Eastman Kodak, Rochester, NY). Both measured and calculated (PB and XVMC) dose distributions were compared regarding profiles and isodoses. Then, 35 lung plans originally created for clinical treatment by PB calculation with the Eclipse planning system (Varian Medical Systems, Palo Alto, CA) were recalculated by XVMC (investigational implementation in PrecisePLAN [Elekta AB, Stockholm, Sweden]). Clinically relevant dose-volume parameters for target and lung tissue were compared and analyzed statistically.nnnRESULTSnThe XVMC calculation agreed well with film measurements (<1% difference in lateral profile), whereas the deviation between PB calculation and film measurements was up to +15%. On analysis of 35 clinical cases, the mean dose, minimal dose and coverage dose value for 95% volume of gross tumor volume were 1.14 ± 1.72 Gy, 1.68 ± 1.47 Gy, and 1.24 ± 1.04 Gy lower by XVMC compared with PB, respectively (prescription dose, 30 Gy). The volume covered by the 9 Gy isodose of lung was 2.73% ± 3.12% higher when calculated by XVMC compared with PB. The largest differences were observed for small lesions circumferentially encompassed by lung tissue.nnnCONCLUSIONSnPencil beam dose calculation overestimates dose to the tumor and underestimates lung volumes exposed to a given dose consistently for 15-MV photons. The degree of difference between XVMC and PB is tumor size and location dependent. Therefore XVMC calculation is helpful to further optimize treatment planning.

[Is cardiotoxicity still an issue after breast-conserving surgery and could it be reduced by multifield IMRT?].

Hintergrund:Die postoperative Strahlentherapie bei Mammakarzinom kann die Lokalrezidivwahrscheinlichkeit deutlich reduzieren. Ein Überlebensvorteil durch die Strahlentherapie nach brusterhaltender Operation war allerdings lange Zeit nicht nachweisbar, was sich u.a. auf eine durch Kardiotoxizität bedingte Übersterblichkeit der bestrahlten Patientinnen zurückführen ließ.Material und Methodik :Die vorliegende Literatur zur Bestrahlung des Mammakarzinoms wurde hinsichtlich der Kardiotoxizität gesichtet und diente als Basis zur Hypothesenbildung.Ergebnisse:Zahlreiche Studien untersuchten in der Vergangenheit das kardiotoxische Potential der Mammabestrahlung. In der Synopsis zeichnet sich dabei folgendes Muster ab: Serien mit eindeutig dokumentierter hoher Herzbelastung (Postmastektomie- und Postlumpektomie-Bestrahlung) gingen mit klar erhöhter kardialer Toxizität einher. Wenn technikbedingt für beide Behandlungsparadigmata eine Herzbelastung durch den Primärstrahl ausgeschlossen werden konnte (überwiegend jüngere Postlumpektomieserien), war keine Toxizität nachweisbar. Unter den Serien mit unklarer Herzbelastung fanden sich sowohl solche mit als auch ohne erhöhte Kardiotoxizität. Eine exakte Quantifizierung, welche Toleranzdosen abhängig von unterschiedlichen geometrischen Dosisverteilungen gelten, ist aufgrund der retrospektiv oft nicht eindeutig feststellbaren individuellen Dosisbelastung bisher kaum möglich. Insbesondere kann gegenwärtig nicht abgeschätzt werden, ab welchem linksseitig durch Tangentenbestrahlung mit hohen Dosen bestrahlten Herzvolumen eine intensitätsmodulierte Strahlentherapie (IMRT) mit ihrer typischen Dosisverteilungscharakteristik (größeres exponiertes Volumen mit niedriger Gesamt- und Einzelmaximaldosis, aber höherer mittlerer/medianer Herzdosis) vorzuziehen wäre.Schlussfolgerung:Die vorliegende Übersichtsarbeit aktualisiert die Datenbasis zur Kardiotoxizität der Mammabestrahlung und betrachtet diese besonders im Hinblick auf die Konsequenzen, die sich für die klinische Einführung der Mamma-IMRT ergeben. Die Mehrfelder-IMRT kann möglicherweise für die kleine Hochrisikogruppe mit ungünstiger Thoraxgeometrie das kardiale Risiko senken. Aufgrund der weiterbestehenden Unsicherheiten bezüglich des Zweittumorrisikos in der kontralateralen Mamma, der kardialen Auswirkung niedriger/intermediärer Dosen auf größere Herzvolumina und der langen Latenz bis zur klinischen Manifestation kardialer Toxizität sollte die klinische Einführung der Mamma-IMRT kontrolliert unter Überwachung mit funktionellen Untersuchungen geschehen.Background:Postoperative radiotherapy after breast cancer surgery effectively reduces local relapses. A survival benefit after breast conservation, however, has only been proven recently which was in part due to excessive cardiac mortality of patients who had been treated with radiotherapy in the past.Material and Methods:The literature on postoperative radiotherapy for breast cancer was reviewed with regard to cardiac toxicity as the basis for hypothesis generation.Results:From numerous publications on cardiac toxicity of breast cancer radiotherapy, the following pattern emerges: in series where a high radiation dose was applied to a significant percentage of the heart (postmastectomy and postlumpectomy series) cardiac toxicity/mortality was increased versus a nonexposed cohort or for left over right disease. If, however, a relevant exposure of cardiac muscle could be more or less excluded based on the technique used (mainly more recent postlumpectomy radiotherapy), no cardiac toxicity was observed. Series for which individual dose exposure varied or could not be clarified also came to varying conclusions. Also due to retrospectively unclear dose distributions, an exact quantification of tolerance doses/effects of different geographic dose distribution patterns could not be performed to date. A particularly difficult question to answer is the threshold volume for clinically relevant cardiotoxicity with tangential radiotherapy at prescription doses. As a consequence, this precludes an estimate in which situations multifield intensity-modulated radiotherapy (IMRT) with its characteristic dose distribution pattern of a larger volume exposed to intermediate doses and higher mean/median heart doses (as shown in Figure 1) might be preferable.Conclusion:This review updates the database on cardiac toxicity of breast cancer radiotherapy with special emphasis regarding the issues related to the clinical use of IMRT. Multifield IMRT may reduce the cardiac risk for a small subset of patients at excessive risk with conventional tangential radiotherapy due to unfavorable thoracic geometry, for whom partial-breast radiotherapy is not an option. Due to further concern about the effects of intermediate doses to larger heart volumes, potentially increased contralateral cancer risk and the long latency of clinically apparent toxicity, the introduction of breast IMRT should be closely followed. Accompanying functional studies may have the potential to detect cardiac toxicity at an earlier time.BACKGROUNDnPostoperative radiotherapy after breast cancer surgery effectively reduces local relapses. A survival benefit after breast conservation, however, has only been proven recently which was in part due to excessive cardiac mortality of patients who had been treated with radiotherapy in the past.nnnMATERIAL AND METHODSnThe literature on postoperative radiotherapy for breast cancer was reviewed with regard to cardiac toxicity as the basis for hypothesis generation.nnnRESULTSnFrom numerous publications on cardiac toxicity of breast cancer radiotherapy, the following pattern emerges: in series where a high radiation dose was applied to a significant percentage of the heart (postmastectomy and postlumpectomy series) cardiac toxicity/mortality was increased versus a nonexposed cohort or for left over right disease. If, however, a relevant exposure of cardiac muscle could be more or less excluded based on the technique used (mainly more recent postlumpectomy radiotherapy), no cardiac toxicity was observed. Series for which individual dose exposure varied or could not be clarified also came to varying conclusions. Also due to retrospectively unclear dose distributions, an exact quantification of tolerance doses/effects of different geographic dose distribution patterns could not be performed to date. A particularly difficult question to answer is the threshold volume for clinically relevant cardiotoxicity with tangential radiotherapy at prescription doses. As a consequence, this precludes an estimate in which situations multifield intensity-modulated radiotherapy (IMRT) with its characteristic dose distribution pattern of a larger volume exposed to intermediate doses and higher mean/median heart doses (as shown in Figure 1) might be preferable.nnnCONCLUSIONnThis review updates the database on cardiac toxicity of breast cancer radiotherapy with special emphasis regarding the issues related to the clinical use of IMRT. Multifield IMRT may reduce the cardiac risk for a small subset of patients at excessive risk with conventional tangential radiotherapy due to unfavorable thoracic geometry, for whom partial-breast radiotherapy is not an option. Due to further concern about the effects of intermediate doses to larger heart volumes, potentially increased contralateral cancer risk and the long latency of clinically apparent toxicity, the introduction of breast IMRT should be closely followed. Accompanying functional studies may have the potential to detect cardiac toxicity at an earlier time.