M. Mast

Left-sided breast cancer radiotherapy with and without breath-hold: does IMRT reduce the cardiac dose even further?

PURPOSE In radiotherapy for left-sided breast cancer, Active Breathing Control enables a decrease of cardiac and Left Anterior Descending (LAD) coronary artery dose. We compared 3D-Conformal (3D-CRT) to Intensity Modulated Radiotherapy (IMRT) treatment plans based on free-breathing (FB) and breath-hold (BH). We investigated whether IMRT enables an additional decrease of cardiac dose in radiotherapy plans with and without BH. METHODS AND MATERIALS Twenty patients referred for whole breast irradiation were included. The whole breast, heart and LAD-region were contoured. Four treatment plans were generated: FB_3D-CRT; FB_IMRT; BH_3D-CRT; BH_IMRT. Several doses were obtained from Dose Volume Histograms and compared. Results were compared statistically using the Wilcoxin Signed Rank Test. For heart and LAD-region, a significant dose reduction was found in BH (p<0.01). For both BH and FB, a significant dose reduction was found using IMRT (p<0.01). By using IMRT an average reduction of 5% was noted in the LAD-region for the volume receiving 20Gy. In 5 cases, the LAD-region remained situated in the vicinity of the radiation portals even in BH. Nevertheless, with IMRT the LAD dose was reduced in these cases. CONCLUSION IMRT results in a significant additional decrease of dose in the heart and LAD-region in both breath-hold and free-breathing.

Magnetic Resonance Imaging– Versus Computed Tomography–Based Target Volume Delineation of the Glandular Breast Tissue (Clinical Target Volume Breast) in Breast-Conserving Therapy: An Exploratory Study

PURPOSE To examine MRI and CT for glandular breast tissue (GBT) volume delineation and to assess interobserver variability. METHODS AND MATERIALS Fifteen breast cancer patients underwent a planning CT and MRI, consecutively, in the treatment position. Four observers (two radiation oncologists and two radiologists) delineated the GBT according to the CT and separately to the MR images. Volumes, centers of mass, maximum extensions with standard deviations (SD), and interobserver variability were quantified. Observers viewed delineation differences between MRI and CT and delineation differences among observers. RESULTS In cranio-lateral and cranio-medial directions, GBT volumes were delineated larger using MRI when compared with those delineated with CT. Center of mass on MRI shifted a mean (SD) 17% (4%) into the cranial direction and a mean 3% (4%) into the dorsal direction when compared with that on the planning CT. Only small variations between observers were noted. The GBT volumes were approximately 4% larger on MRI (mean [SD] ratio MRI to CT GBT volumes, 1.04 [0.06]). Findings were concordant with viewed MRI and CT images and contours. Conformity indices were only slightly different; mean conformity index was 77% (3%) for MRI and 79% (4%) for CT. Delineation differences arising from personal preferences remained recognizable irrespective of the imaging modality used. CONCLUSIONS Contoured GBT extends substantially further into the cranio-lateral and cranio-medial directions on MRI when compared with CT. Interobserver variability is comparable for both imaging modalities. Observers should be aware of existing personal delineation preferences. Institutions are recommended to review and discuss target volume delineations and to design supplementary guidelines if necessary.

MRI- versus CT-based volume delineation of lumpectomy cavity in supine position in breast-conserving therapy: an exploratory study.

PURPOSE To examine magnetic resonance imaging (MRI) and computed tomography (CT) for lumpectomy cavity (LC) volume delineation in supine radiotherapy treatment position and to assess the interobserver variability. METHODS AND MATERIALS A total of 15 breast cancer patients underwent a planning CT and directly afterward MRI in supine radiotherapy treatment position. Then, 4 observers (2 radiation oncologists and 2 radiologists) delineated the LC on the CT and MRI scans and assessed the cavity visualization score (CVS). The CVS, LC volume, conformity index (CI), mean shift of the center of mass (COM), with the standard deviation, were quantified for both CT and MRI. RESULTS The CVS showed that MRI and CT provide about equal optimal visibility of the LC. If the CVS was high, magnetic resonance imaging provided more detail of the interfaces of the LC seroma with the unaffected GBT. MRI also pictured in more detail the interfaces of axillary seromas (if present) with their surroundings and their relationship to the LC. Three observers delineated smaller, and one observer larger, LC volumes comparing the MRI- and CT-derived delineations. The mean ± standard deviation CI was 32% ± 25% for MRI and 52% ± 21% for CT. The mean ± standard deviation COM shift was 11 ± 10 mm (range 1-36) for MRI and 4 ± 3 mm (range 1-10) for CT. CONCLUSIONS MRI does not add additional information to CT in cases in which the CVS is assessed as low. The conformity (CI) is lower for MRI than for CT, especially at a low CVS owing to greater COM shifts for MRI, probably caused by inadequate visibility of the surgical clips on magnetic resonance (MR) images. The COM shifts seriously dictate a decline in the CI more than the variability of the LC volumes does. In cases in which MRI provides additional information, MRI must be combined with the CT/surgical clip data.

ConPas: a 3-D Conformal Parotid Gland-Sparing Irradiation Technique for Bilateral Neck Treatment as an Alternative to IMRT

Background and Purpose:Intensity-modulated radiotherapy (IMRT) is used in most reported techniques for bilateral neck irradiation that aim at parotid gland sparing. A relatively simple conformal parotid-sparing technique (ConPas) was developed that uses no beam-intensity modulation. The purpose of this paper is to demonstrate, in patients with larynx or hypopharynx carcinoma, that ConPas enables adequate coverage of the primary tumor and the bilateral neck nodes, while keeping the mean parotid dose (MPD) < 26 Gy.Patients and Methods:Treatment plans using ConPas and the conventional technique (using one anteroposterior supraclavicular and two lateral beams) were computed for ten consecutive patients with T1–4 N0–1 larynx or hypopharynx carcinoma (not T1 glottic). A dose of 46 Gy was prescribed to the primary tumor and the bilateral neck nodes, planned either with the conventional technique or ConPas, followed by a boost up to 70 Gy with a simple two-field technique. The target coverage of both techniques was compared using the V95, the percentage of the planning target volume (PTV) of the primary tumor and nodal regions receiving at least 95% of the prescribed elective dose. The MPDs and the normal-tissue complication probabilities (NTCPs) of the parotid glands were compared using either technique including the boost up to 70 Gy. Dosimetric verification of the technique has been carried out, using ionization chamber measurements and film dosimetry.Results:The mean V95 was 85.2% and 91.2% (p = 0.08), the mean MPD 38.7 Gy and 25.4 Gy (p < 0.001), and the mean NTCP for the parotid glands 0.87 and 0.22 (p < 0.001) for the conventional technique and ConPas, respectively. The dosimetric verification shows a good agreement between dose calculation and measurement.Conclusion:ConPas enables adequate target coverage and clinically relevant parotid sparing in bilateral neck irradiation without beam-intensity modulation.Hintergrund und Ziel:Die intensitätsmodulierte Strahlentherapie (IMRT) ist die am häufigsten beschriebene Technik für bilaterale Halsbestrahlung mit Schonung der Parotis. Eine relativ einfache, die Parotis aussparende Technik (ConPas [„conformal parotid-sparing technique“]) wurde entwickelt, die keine Intensitätsmodulation benötigt. Ziel dieser Studie ist zu zeigen, dass bei Patienten mit Larynx- oder Hypopharynxkarzinom mit ConPas eine adäquate Dosisabdeckung des Primärtumors und der bilateralen Lymphknoten erreicht werden kann, wobei die gemittelte Dosis in der Parotis (MDP) < 26 Gy liegt.Patienten und Methodik:Für zehn konsekutive Patienten mit Larynx- und Hypopharynxkarzinom (T1–4 N0–1) wurde sowohl ein Bestrahlungsplan mit der ConPas-Technik als auch mit der konventionellen Technik (zwei seitliche Felder und ein anteroposteriores supraklavikuläres Feld) erstellt. Zuerst wurden die Patienten mit ConPas bzw. konventioneller Technik bis 46 Gy bestrahlt. Danach folgte ein Boost bis 70 Gy mit einfacher Zwei-Felder-Technik. Die Zielvolumenabdeckungen der beiden Techniken wurden mit Hilfe des V95 (Prozentsatz des Planungszielvolumens [PTV] des Primärtumors und der Lymphknotenregionen, der mindestens 95% der vorgeschriebenen elektiven Dosis erreicht) miteinander verglichen. Die MPD und die NTCP („normal-tissue complication probability“) der Parotiden wurden für beide Techniken verglichen. Dosimetrische Verifikationen wurden mit Ionisationskammer und Filmdosimetrie vorgenommen.Ergebnisse:Das gemittelte V95 lag für die konventionelle Technik bzw. ConPas bei 85,2% bzw. 91,2% (p = 0,08), die gemittelte MPD bei 38,7 Gy bzw. 25,4 Gy (p < 0,001) und die gemittelte NTCP für die Parotis bei 0,87 bzw. 0,22 (p < 0,001). Die dosimetrische Verifikation zeigt eine gute Übereinstimmung zwischen Dosisberechnung und Messungen.Schlussfolgerung:ConPas ermöglicht eine adäquate Zielvolumenabdeckung und eine klinisch relevante Parotisaussparung bei bilateraler Halsbestrahlung ohne Intensitätsmodulation.

Target volume delineation in breast conserving radiotherapy: are co-registered CT and MR images of added value?

IntroductionIn breast conserving radiotherapy differences of target volume delineations between observers do occur. We evaluated whether delineations based on co-registered computed tomography (CT) and magnetic resonance (MR) imaging may result in an improved consistency between observers. We used the delineation conformity index (CI) to compare clinical target volumes of glandular breast tissue (CTV breast) and lumpectomy cavity (LC) on both imaging modalities.Methods and materialsFour observers delineated CTV breast and LC on co-registered CTMR images in ten breast cancer patients. CIs were determined for CT and CTMR. Furthermore, the Cavity Visualization Score (CVS) of LC was taken into account.ResultsThe mean CI for CTV breast (CICT;CTV: 0.82 and CICT-CTMR;CTV: 0.80) and LC (CICT;LC: 0.52 and CICT-CTMR;LC: 0.48) did not differ significantly (p = 0.07 and p = 0.33, respectively). Taking CVS into account for the LC, with a CVS ≥ 4 the mean CI was 0.62 for both CICT;LC and CICT-CTMR;LC.ConclusionThe mean volume of the delineated glandular breast tissue based on CT was significantly larger compared to the volume based on CTMR. For patients with a CVS ≥ 4, the mean CIs of the LC were higher compared to CVS < 4 for volumes delineated on both CT as well as CTMR images. In our study cohort no significant differences between the CIs of the CTV breast and the LC delineated on CTMR co-registered images were found compared to the CIs on CT images only. Adding MR images does not seem to improve consistency of the delineation of the CTV breast and the LC, even though the volumes were copied from CT images. Since we included only ten patients, caution should be taken with regard to the results of our study.

Preradiotherapy Calcium Scores of the Coronary Arteries in a Cohort of Women With Early-Stage Breast Cancer: A Comparison With a Cohort of Healthy Women

PURPOSE Breast cancer radiotherapy has been associated with an increased risk of cardiac toxicity. However, no data are available on the probability of developing coronary artery disease (CAD) in breast cancer patients when compared with healthy women. Therefore, baseline coronary artery calcium (CAC) scores, as an accepted tool to predict CAD, were determined and compared with the CAC scores of a healthy, asymptomatic cohort, the Multi-Ethnic Study of Atherosclerosis (MESA) cohort. METHODS AND MATERIALS Eighty consecutive patients with ductal carcinoma in situ or infiltrative breast cancer referred for radiotherapy after breast-conserving surgery were included in our study. Their cardiovascular risk profile was registered, and a 64 multislice CT scan was performed. The CAC scores of an unselected (Caucasian only) Radiotherapy Centre West (RCWEST) cohort, as well as of those of a selected (comorbidity and race adjusted) RCWEST cohort, were determined. The scores of both cohorts were compared with those of the female (Caucasian only) MESA cohort. RESULTS For the unselected RCWEST cohort (n = 62) we found significant (p < .01) higher scores for women in the 55-64 age category compared with those of the MESA cohort. In the selected cohort (n = 55) the CAC scores of the women in the age category 55-64 were significantly (p = .02) higher compared with the MESA cohort. No significant differences were noted in the other age categories. CONCLUSION Both cohorts revealed that CAC scores in the 55-64 age category were significantly higher than the CAC scores in the asymptomatic (female) MESA population. These data suggest that breast cancer patients bear a higher risk of developing coronary heart disease before the start of radiotherapy. Therefore, measures to decrease cardiac dose further in breast cancer radiotherapy are even more important.

Tangential IMRT versus TomoTherapy with and without breath-hold in left-sided whole breast irradiation

Whole breast irradiation (Wbi), with or without a boost dose, is considered to be the standard therapy after breast conserving surgery. However, Wbi may, amongst others, induce ischemic heart disease. The incidence of ischemic heart disease appears to be proportional to the mean dose to the heart and starts within a few years after exposure [1]. Furthermore, given its anatomical location, the left anterior descending (Lad) coronary artery is the cardiac artery that is most at risk for developing atherosclerosis after left-sided breast-conserving radiotherapy [2]. it is, therefore, of great importance to define the most optimal radiation treatment technique for left-sided Wbi. The aims are achieving the lowest dose in critical structures, the heart and the Lad, as well as administering optimal target coverage. using a breath-hold technique during left-sided breast cancer radiotherapy reduces the dose in the heart [3]. We found that tangential beam intensity modulated radiotherapy (iMRT) in combination with a breath-hold technique, resulted in a significantly larger decrease of the dose in the heart and Lad when compared to 3d-CRT with breath-hold [4]. However, others reported that TomoTherapy resulted in less dose in the critical structures when compared to tangential iMRT [5,6]. The question is, does this finding still hold when tangential iMRT is used with a breath-hold technique, since, currently, no breath-hold can be applied when using a TomoTherapy technique. The aim of this comparative planning study, therefore, was to determine whether with a breath-hold technique a further dose reduction to the heart and the Lad-region could be obtained with TomoTherapy when compared to tangential iMRT.

Two years’ experience with inspiration breath-hold in liver SBRT

Highlights • The workflow of inspiration breath-hold SBRT for liver metastases is described.• Inspiration breath-hold in liver SBRT is feasible for 95% of the patients.• An individual margin recipe for inspiration breath-hold liver SBRT is explained.• Margin reduction of 10 mm using inspiration breath-hold compared to free breathing.

SU-E-J-201: Position Verification in Breast Cancer Radiotherapy Using Tantalum Clips in the Lumpectomy Cavity

PURPOSE To find out whether tantalum surgical clips can be used for online position verification in treatment of the lumpectomy cavity (LC) in breast cancer patients. Tantalum is a high density metal that could be visible on Electronic Portal Images (EPIs) and be an affordable alternative to gold markers. Clips are considered more representative for the LC position than nearby bony structures. METHODS In twelve patients the surgeon had placed 2 to 5 tantalum clips in the LC. The AP and lateral fields used for portal imaging, were adapted. In doing so, both bony structures and tantalum clips were visible on EPIs. The following analyses were performed:1. Image degradation, with respect to delineating the CTV, of the axial CT slices by artefacts because of the tantalum clips was evaluated by a radiation oncologist;2. The visibility of the tantalum clips on the EPIs was evaluated by four radiation therapists (RTTs);3. Bony anatomy and tantalum clip matches were performed on the same images independently by two observers. RESULTS 1. Delineation of the CTV by the radiation oncologist was not hampered by CT image artefacts because of the clips.2. The mean score for visibility of the clips on the EPIs, analysed by the four RTTs, was 5.6 on a scale of 10 (range 3.9 - 8.0).3. In total 12 patients with 16 fractions each were analysed. The differences between clip match and bone match are significant with a mean vector length of 5.2 mm (SD 1.9 mm) for the difference. CONCLUSION Results of matches on tantalum clips as compared to matches on bony structures differ substantially. Therefore clip matches can result in smaller CTV to PTV margins than bone matches. Visibility of the clips on EPIs is sufficient, so they can be an alternative to gold markers.