Left Lung V20 Research Articles

Dosimetric evaluation of different radiotherapy techniques in mastectomized left-sided breast cancer.

Inclusion of internal mammary lymph nodes in mastectomized left breast cancer radiotherapy may lead to high dose receiving risk of the heart, lung, and contralateral breast. The aim of this study is to compare the dosimetric differences of field-in-field (FIF), volumetric-modulated arc therapy (VMAT), seven-field intensity-modulated radiotherapy (7F-IMRT), and helical tomotherapy (HT) planning techniques for mastectomized left breast cancer. Computed tomography images of ten patients treated with the FIF technique were used to compare four different treatment planning techniques. Planning target volume (PTV) included chest wall and regional lymph nodes. The heart, left anterior descending coronary artery (LAD), left and whole lung, thyroid, esophagus, and contralateral breast were identified as organs-at-risks (OARs). Except for HT, a single isocenter in PTV and bolus of thickness 0.3 cm on the chest wall was used. Complete and directional blocks were applied in HT, and the dosimetric parameters of PTV and OARs for four different techniques were analyzed using the Kruskal-Wallis test. 7F-IMRT, VMAT, and HT were superior to the FIF technique in providing homogeneous dose distribution covering the PTV (P < 0.0001). Mean doses (Dmean) of the contralateral breast and esophagus, lung, and body-PTV V5 (volume receiving 5 Gy) were reduced in FIF, whereas in the HT, Heart Dmean, LAD Dmean , Dmax, healthy tissue (body-PTV) Dmean , heart and left lung V20, and thyroid V30 were significantly reduced (P < 0.0001). FIF and HT techniques were found to be significantly advantageous over 7F-IMRT and VMAT for OARs. Using those three multiple-beam techniques reduced high-dose volumes of healthy tissues and organs in mastectomized left breast cancer radiotherapy but also increased low-dose volumes and contralateral lung and breast doses. Complete and directional blocks applied in HT reduce heart, lung, and contralateral breast doses.

A Dosimetric Study Comparing 3D-CRT vs. IMRT vs. VMAT in Left-Sided Breast Cancer Patients After Mastectomy at a Tertiary Care Centre in Eastern India.

IntroductionPost-mastectomy radiation in left-sided breast cancer in women continues to pose a significant risk to the underlying lungs and heart. This study analyzed the difference in planning target volume (PTV) coverage and dose to the organs at risk (OAR) by using three different planning methods for the same patient - three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT), and volumetric-modulated arc therapy (VMAT).Material and methodsThirty-five left-sided breast cancer patients’ post-mastectomy were included in this study, and three different plans for adjuvant radiation were created using 3D-CRT, IMRT, and VMAT. The prescribed dose was 50Gy in 25 fractions. Kruskal-Wallis analysis of variance (ANOVA) was done, followed by a pairwise t-test to establish a hierarchy of plan quality and dosimetric benefits. The plans were compared with PTV95, homogeneity index (HI), conformity index (CI), hotspot (V107%), left lung V20Gy, mean lung dose, heart V25Gy, mean heart dose, and integral dose (ID) to the body.ResultsBoth VMAT and IMRT led to improved PTV95% coverage (95.63±1.82%, p=0.000 in VMAT; 93.70±2.16 %, p=0.000; 81.40±6.27% in 3D-CRT arm) and improved CI (0.91±0.06 in IMRT [p<0.05] and 0.96±0.02 for VMAT plans [p<0.05]) as compared to 3D-CRT (0.66±0.11), which was statistically significant on pairwise analysis. In contrast, the difference in HI and reduction in hotspots were not significantly different. Left lung V20 was statistically very different between the three arms with the highest values in IMRT (36.64±4.45) followed by 3D-CRT (34.80±2.24) and the most negligible value in VMAT (33.03±4.20). Mean lung dose was also statistically different between the three arms. There was a statistically significant difference in mean heart dose between the three arms on pairwise analysis. Both the inverse planning methods led to a statistically significant increase in low dose volume (V5 and V10) of the ipsilateral lung, opposite lung, and heart, and increased ID to the body excluding the PTV.ConclusionWhile both the inverse planning modalities led to increased coverage, better CI, and better HI and decreased high dose volumes in OARs, there was increased low volume irradiation of heart, lungs, and body with VMAT faring marginally better than IMRT in coverage and decreasing lung irradiation with comparable heart irradiation.

A comparative study evaluating the dose volume parameters in 3D conformal radiation of left sided whole breast irradiation including regional lymphnodes - a need of resource constrained countries.

BackgroundThe purpose of this study was to compare four 3D conformal radiation techniques in treatment of left breast cancer patients.Materials and methodsRadiation was planned for 20 patients to the left breast and regional lymph nodes using four techniques: partially wide tangents, photon-photon mix, photon-electron mix and 30/70 photon-electron mix. All plans were evaluated for internal mammary nodes (IMN) coverage, hotspot and normal tissue constraints.ResultThe 85% of planning target volume (PTV) coverage was lesser for upper IMN than the lower IMN (below the lower border of the clavicular head) for all four techniques. The lower IMN coverage was better for partially wide tangent (80.46%) and photon-photon mix (88.88%). The lowest value of hotspot was seen in the partially wide tangent technique (112.69% ± 1.92). Hotspot is unacceptably high in both photon-electron mix and 30/70 photon-electron mix (> 120%). Left lung mean dose for all techniques on a pair-wise comparison showed no statistical difference. Left lung V20 values for partially wide tangent was 37.56% ± 8.17 and for photon-photon mix it was 40.49% ± 3.36. The mean heart dose with partially wide tangent was 9.43 ± 3.15 Gy and with photon-photon mix it was 10.10 ± 2.70 Gy. The mean heart dose for photon-electron mix was 7.56 ± 1.95 Gy and for 30/70 photon-electron mix it was 7.98 ± 2.16 Gy.ConclusionNo single technique satisfies all the criteria. The decision should be made on a case-by-case basis, considering the anatomy of the patient, availability of electron facilities and setup accuracy and reproducibility.

The effect of deep inspiration breath-hold technique on left anterior descending coronary artery and heart dose in left breast irradiation

PurposeTo determine the effect of the deep inspiration breath-hold (DIBH) technique on left anterior descending coronary artery (LAD) region and heart dose in left breast cancer irradiation.Materials and MethodsTwenty-five left breast cancer patients who previously received breast-conserving surgery underwent computed tomography (CT) simulation with both free-breathing (FB) and DIBH techniques and four radiation treatment plans. The plan comprised the following with both the FB and DIBH techniques: whole breast (WB), and WB with internal mammary lymph nodes (WB+IMNs). The prescription dose was 50 Gy in 25 fractions. The doses to the LAD region, heart and lungs were compared. Moreover, in-field maximum heart distance (maxHD) and breast volume were analyzed for correlations with the mean heart dose (MHD).ResultsIn the WB plan with DIBH vs. FB techniques, the mean radiation doses to the LAD region, MHD, and the left lung V20 were 11.48 Gy vs. 19.84 Gy (p < 0.0001), 2.95 Gy vs. 5.38 Gy (p < 0.0001), and 19.72% vs. 22.73% (p = 0.0045), respectively. In the WB+IMNs plan, the corresponding values were 23.88 Gy vs. 31.98 Gy (p < 0.0001), 6.43 Gy vs. 10.24 Gy (p < 0.0001), and 29.31% vs. 32.1% (p = 0.0009), respectively. MHD correlated with maxHD (r = 0.925) and breast volume (r = 0.6).ConclusionThe use of the DIBH technique in left breast cancer irradiation effectively reduces the radiation doses to the LAD region, heart and lungs. MHD is associated with maxHD and breast size.

Dosimetric Correlation Between The Depth of Chest Wall Expansion and Heart Dose in Left Breast Cancer Irradiation Using Deep Inspiratory Breath Hold Technique

Introduction and Objective: In adjuvant radiotherapy for left breast cancer, a significant heart volume may be included in the radiation field leading to long-term cardiac toxicities. Deep inspiratory breath hold technique (DIBH) leads to chest wall separation away from the heart and thus can reduce the heart dose compared to free breathing technique. The aim of this study is to correlate dosimetrically the degree of chest wall expansion measured on planning 4D-CT scan to the heart dose in left breast cancer irradiation using DIBH technique. Materials and Methods: Thirty four patients with left breast cancer planned for adjuvant radiotherapy were included. All patients were scanned by Varian RPM (Real Time Position Managment) respiratory gating system using infrared reflecting markers and a video camera to detect the respiratory motion. IMRT or VMAT plans were done for all patients with a prescribed dose 50Gy/25fr/5w with or without operative bed boost dose 10Gy/5fr/1w. The degree of chest wall expansion was identified by measuring the amplitude of DIBH breathing curve from baseline in planning 4D-CT scan in centimeters. The depth of expansion was correlated dosimetrically with the heart V20, V30, and mean heartdose. Results: The mean distance of chest wall expansion was 2.9cm. The mean left lung dose was 8.6Gy. The mean left lung V20 was 13.8%. The mean heart dose was 1.8Gy. The mean heart V30 was 0.6%. A statistically significant reduction of the mean heart dose and V30 was observed with chest wall expansion of 1.4cm or higher (p&lt;0.05). Conclusion: In DIBH technique, the depth of chest wall expansion in 4DCT planning is dosimetrically correlated with the cardiac dose reduction during adjuvant irradiation of left breast cancer. Further clinical studies are needed to translate this dosimetric advantage into clinical benefit.

Evaluation of abches and volumetric modulated arc therapy under deep inspiration breath-hold technique for patients with left-sided breast cancer: A retrospective observational study.

Radiotherapy after breast-conserving surgery or mastectomy has clinical benefits including reducing local recurrence and improving overall survival. Deep inspiration breath-hold (DIBH) technique using the Abches system is an easy and practical method to reduce radiation dose to the heart and lungs. This retrospective study was proposed to investigate the dosimetric difference between Abches system and free breathing technique in treating left-sided breast cancer.Eligible patients underwent computed tomography (CT) scans to acquire both free breathing (FB) and DIBH technique data using the Abches. For each patient, both FB and DIBH image sets were planned based on the volumetric modulated arc therapy (VMAT). Radiation dose to the heart, ipsilateral lung, and contralateral lung was compared between the Abches system and FB.No significant differences in the planning target volume (PTV) (674.58 vs 665.88 cm3, P = .29), mean dose (52.28 vs 52.03 Gy, P = .13), and volume received at the prescribed dose (Vpd) (94.66% vs 93.92%, P = .32) of PTV were observed between the FB and DIBH plans. Significant differences were found in mean heart (6.71 Gy vs 4.21 Gy, P < .001), heart V5 (22.73% vs 14.39%, P = .002), heart V20 (10.96% vs. 5.62%, P < .001), mean left lung (11.51 vs 10.07 Gy, P = .01), left lung V20 (22.88% vs 19.53%, P = .02), left lung V30 (18.58 vs 15.27%, P = .005), and mean right lung dose (.89 vs 72 Gy, P = .03).This is the first report on reduced mean left lung, mean right lung dose, and V20 of left lung using VMAT and Abches. The combination of Abches and VMAT can practically and efficiently reduce extraradiation doses to the heart and lungs.

Dosimetric comparison of deep-inspiration breath-hold and free-breathing treatment delivery techniques for left-sided breast cancer using 3D surface tracking

IntroductionWhile radiation therapy has been shown to increase local control and overall survival for breast cancer, late cardiac toxicity remains a concern. Morbidity and mortality have been shown to increase proportionally to the mean heart dose. Deep inspiration breath-hold (DIBH) can reduce heart dose compared to free-breathing (FB) by increasing the heart-to-chest wall distance, especially in left-sided breast cancer. We present our clinical experience with DIBH in left breast and chest-wall irradiation using 3D optical surface tracking. Materials & Methods29 patients were treated with DIBH using a surface tracking system that provides a real time 3D surface image of the patient. Comparisons of maximum and mean heart dose, heart-chest wall separation, and the percentage of lung volume that receives 20 or more Gy (V20) between the DIBH and hypothetical FB treatment plans were conducted with the Student's t-test. Correlation coefficients were also calculated for heart-chest wall separation, heart volume, and lung volume. ResultsComparing DIBH and FB plans showed a decrease in mean and maximum heart doses in all patients. Individual mean heart doses decreased by an average of 1.12 Gy, and the average mean heart dose for DIBH plans was significantly lower than corresponding FB plans (1.02 vs. 2.12 Gy; p < 0.0001). Maximum heart dose decreased by an average of 11.88 Gy and was significantly lower in DIBH versus FB plans (28.33 vs. 43.7 Gy; p = 0.0001). The average difference in heart to chest-wall separation between DIBH and FB images was 2.41 cm. DIBH left lung volume and measured increases in volume on inspiration inversely correlated with maximum heart dose (R = 0.39) and left lung V20 (R = 0.32). ConclusionsDIBH with 3D surface tracking can significantly benefit patients with left sided disease by limiting the mean and maximum heart dose. DIBH appears to viably reduce heart dose for left-breast cancer patients and thus potentially reduce long-term complications without prolonging treatment delivery.

Dosimetric Analysis of Three Different Radiotherapy Techniques in Patients with Breast Cancer and Their Impact on Organs at Risk (OAR)

Aim: Dosimetric analysis of three different Radiotherapy techniques in patients with Breast Cancer and their impact on OAR’s. Materials and Methods: 12 patients of Carcinoma Breast who received breast radiotherapy were selected for analysis. Computed tomography (CT) simulation image data sets were retrieved. Planning target Volume (PTV), heart and ipsilateral lung were contoured for planning and analysis of doses. Three different plans using conventional bi-tangential fields were prepared, Plan 1 with SAD full beam with wedge (SAD-FBW), Plan 2 with SSD half beam with wedge (SSD-HBW) and plan 3 with SSD half beam without wedge techniques (SSD-HBO) in CMS Xio TPS. Statistical analysis was done using SPSS version 16.0. Results: The PTV coverage was significantly better in SAD-FBW techniques when compared with the other two techniques i.e. SSD-HBW (mean = 92.33, SD = 4.69, p = 0.005) and SSD-HBO (mean = 75.05, SD = 11.92, p = 0.002). The mean heart doses were significantly better in SAD-FBW compared to SSD-HBW (mean = 3.75, SD = 2.27, p = 0.017) but in SSD-HBO technique mean heart doses were better than SAD-FBW technique (mean = 3.27, SD = 1.94, p = 0.004). Similarly, the left lung V20 values were significantly better in SSD-HBO technique than SAD-FBW technique (mean = 11.75, SD = 4.34, p = 0.004) but there was statistically insignificant difference between the SAD-FBW and SSD-HBW techniques. The treatment monitor units were significantly less in SAD-FBW compared to SSD-HBW but SSD-HBO has less MU compared to SAD-FBW technique. Conclusion: SAD Full Beam with wedge technique is practically better than SSD Half Beam technique with or without wedge without compromising PTV coverage considering other dosimetric parameters. We also recommend that centers treating patient with half beam SSD techniques should shift immediately to SAD techniques.

Dosimetric Comparison of Deep Inspiration Breath Hold and Free Breathing Treatment Techniques for Left-sided Breast Cancer Using 3-Dimensional Surface Tracking

While radiation therapy has been shown to increase local control and overall survival for breast cancer, cardiac toxicity remains a concern. Morbidity and mortality have been shown to increase proportionally to the mean heart dose. Deep inspiration breath hold (DIBH) can reduce heart dose compared to free-breathing (FB) delivery by increasing the distance from the heart to the chest wall, especially in left-sided breast cancer. DIBH requires monitoring of patients' respiratory motion. We report our experience with DIBH in left breast and chest-wall irradiation using 3D optical surface tracking. Thirty patients were treated using DIBH with a surface tracking system that provides a real time 3D surface image of the patient. This image is registered with the patient's body contour to facilitate setup and provide real time position offsets. Treatment plans were created on FB and DIBH images to compare doses to the heart and lungs. The distance between the heart and chest wall was measured at the 7th thoracic vertebra at 11 cm anterior to the spinal canal. Unpaired t-test was used to compare means and mean differences in heart and lung doses between plans. Correlation coefficients were derived for anatomic variances, such as heart and chest wall separation as well as heart and lung volumes. A comparison of DIBH and FB plans showed a decrease in mean and maximum heart doses in all patients. Individual patients’ mean heart doses decreased by an average of 1.12 Gy, and the average mean heart dose for DIBH plans was significantly lower than for FB plans (1.02 vs 2.12 Gy; P<0.0001). When lumpectomy and mastectomy patients were separated, this statistical significance was maintained in each group (P<0.0001 and P = 0.0233, respectively). Maximum heart dose decreased by an average of 11.88 Gy and was significantly lower in DIBH plans versus FB plans (28.33 vs 43.7 Gy; P = 0.0001). The average difference in heart to chest-wall separation between DIBH and FB images was 2.41 cm. This difference correlated positively with mean (R = 0.24) and maximum (R = 0.51) heart doses. While a trend towards improved left lung V20 was noted (14.04 vs 15.78%; P = 0.057), a significant difference was noted only for intact breast patients treated with opposed tangents alone (12.25 vs 15.06 Gy; P = 0.0257) versus plans with additional regional nodal radiation fields. Heart volume did not correlate with any measurements. However, DIBH left lung volume and the measured increase in volume on inspiration inversely correlated with maximum heart dose (R = 0.39) and left lung V20 (R = 0.32). DIBH with 3D surface tracking can significantly benefit patients with left sided disease by limiting the mean and maximum heart dose. In addition, DIBH showed a trend in improving lung V20 in intact breast patients treated with tangents alone. DIBH appears to be a viable option to reduce heart dose for left sided breast cancer patients and thus potentially reduce long-term complications without prolonging treatment delivery.

SU‐E‐T‐18: A Comparison of Planning Techniques for Bilateral Reconstructed Chest Wall Patients Undergoing Whole Breast Irradiation

Purpose:As we continuously see more bilateral reconstructed chest wall cases, new challenges are being presented to deliver left‐sided breast irradiation. We herein compare three Deep Inspiration Breath Hold (DIBH) planning techniques (tangents, VMAT, and IMRT) and two free breathing techniques (VMAT and IMRT).Methods:Three left‐sided chest wall patients with bilateral implants were studied. Tangents, VMAT, and IMRT plans were created for DIBH scans. VMAT and IMRT plans were created for free breathing scans. All plans were normalized so that 95% of the prescription dose was delivered to 95% of the planning target volume (PTV). The maximum point dose was constrained to less than 120% of the prescription dose. Since the success of DIBH delivery largely depends on patient's ability to perform consistent breath hold during beam on time, smaller number of Monitor Units (MU) is in general desired. For each patient, the following information was collected to compare the planning techniques: heart mean dose, left and right lung V20 Gy, contra‐lateral (right) breast mean dose, cord max dose, and MU.Results:The average heart mean dose over all patients are 1561, 692, 985, 1245, and 1121 cGy, for DIBH tangents, VMAT, IMRT, free breathing VMAT and IMRT, respectively. For left lung V20 are 60%, 28%, 26%, 30%, and 29%. For contra‐lateral breast mean dose are 244, 687, 616, 783, 438 cGy. MU are 253, 853, 2048, 1035, and 1874 MUs.Conclusion:In the setting of bilateral chest wall reconstruction, opposed tangent beams cannot consistently achieve desired heart and left lung sparing. DIBH consistently achieves better healthy tissue sparing. VMAT appears to be preferential to IMRT for planning and delivering radiation to patients with bilaterally reconstructed chest walls being treated with DIBH.

Can Proton Therapy Improve the Therapeutic Ratio in Breast Cancer Patients at Risk for Nodal Disease?

Regional node irradiation in patients with invasive breast cancer often results in increased radiation exposure to organs at risk. We evaluated the potential advantages of 3-dimensional conformal photon+proton therapy (3DCX+PT) in treating regional nodes versus photon-electron (3DCRT) or intensity-modulated radiotherapy (IMRT). Ten left-sided breast cancer patients underwent radiation treatment planning. 3DCX+PT, 3DCRT, and IMRT plans were generated for each patient. There was no significant difference in target coverage between 3DCX+PT and IMRT. However, coverage of level II axillary lymph nodes was inferior with 3DCRT with a median D95 of 45 versus 50 Gy with either IMRT (P=0.0006) or 49.5 CGE with 3DCX+PT (P=0.0033). Internal mammary nodes coverage was also inferior with 3DCRT (median D95 was 42 Gy) compared with 47 Gy with IMRT (P=0.043) or 48.5 CGE with 3DCX+PT (P=0.0068).With 3DCX+PT, left lung V20 and V5 were 31% and 50% versus 36% (P=0.0368) and 70% (P=0.0007) with 3DCRT and 30% (P=0.7328) and 81% (P=0.0002) for IMRT. 3DCX+PT resulted in heart V20 and heart V5 of 0% and 7%, respectively, versus 4% (P=0.0067) and 24% (P=0.0002) with 3DCRT and 21% (P=0.0001), 50% (P=0.0001) with IMRT. The IMRT plans produced significantly higher integral, contralateral lung, and breast doses. Regional node target coverage was inferior with 3DCRT compared with either IMRT or 3DCX+PT. Organs at risk were exposed to less radiation with 3DCX+PT compared with 3DCRT or IMRT. Proton treatment offered both improved coverage of the regional lymph nodes and decreased dose to the heart, lung, and contralateral normal tissue.

Single Field Spot-Scanning (SFSS) Is Dosimetrically Superior to 2-Field Intensity Modulated Proton Therapy (IMPT) for Proton Postmastectomy Radiation Therapy (PMRT)

Single Field Spot-Scanning (SFSS) Is Dosimetrically Superior to 2-Field Intensity Modulated Proton Therapy (IMPT) for Proton Postmastectomy Radiation Therapy (PMRT)

TU‐F‐17A‐06: Motion Stability and Dosimetric Impact of Spirometer‐Based DIBH‐RT of Left‐Sided Breast Cancer

Purpose:Patients undergoing radiotherapy (RT) for left‐sided breast cancer have increased risk of coronary artery disease. Deep Inhalation Breath Hold assisted RT (DIBH‐RT) is shown to increase the geometric separation of the target area and heart, reducing cardiac radiation dose. The purposes of this study are to use Cine MV portal images to determine the stability of spirometer‐guided DIBH‐RT and examine the dosimetric cardiopulmonary impact of this technique.Methods:Twenty consecutive patients with left‐sided breast cancer were recruited to the IRB‐approved study. Free‐breathing (FB) and DIBH‐CT's were acquired at simulation. Rigid registration of the FB‐CT and DIBH‐CT was performed using primarily breast tissue. Treatment plans were created for each FB‐CT and DIBH‐CT using identical paired tangent fields with field‐in‐field or electronic compensation techniques. Dosimetric evaluation included mean and maximum (Dmax) doses for the left anterior descending artery (LAD), mean heart dose, and left lung V20. Cine MV portal images were acquired for medial and lateral fields during treatment. Analysis of Cine images involved chest wall segmentation using an algorithm developed in‐house. Intra‐ and inter‐fractional chest wall motion were determined through affine registration to the first frame of each Cine.Results:Dose to each cardiac structure evaluated was significantly (p&lt;0.001) reduced with the DIBH plans. Mean heart dose decreased from 2.9(0.9–6.6) to 1.6(0.6–5.3) Gy; mean LAD dose from 16.6(3–43.6) to 7.4(1.7–32.7) Gy; and LAD Dmax from 35.4 (6.1–53) to 18.4(2.5–51.2) Gy. No statistically significant reduction was found for the left lung V20. Average AP and SI median chest wall motion (intrafractional) was 0.1 (SD=0.9) and 0.5 (SD=1.1) mm, respectively. Average AP inter‐fractional chest wall motion was 2.0 (SD=1.4) mm.Conclusion:Spirometer‐based DIBH treatments of the left breast are reproducible both inter‐ and intra‐fractionally, and provide a statistically and potentially clinically useful dosimetric advantage to cardiac structures.

SU-E-T-609: Impact of Breath-Hold Level, Age, and BMI on Normal Tissue Dosimetry for Left Breast Cancer Patients

Purpose: This study evaluates dose to heart, left anterior descending coronary artery (LAD) and left lung as a function of breath‐hold level, age and body mass index (BMI), for patients undergoing deep‐inspiration breath‐hold (DIBH) treatments for left breast cancer. Methods: The study involved 35 patients with free‐breathing and breath‐hold CT scans. The RPM System (Varian Oncology Systems, Palo Alto, Ca) was used to measure breath‐hold level which is defined as the distance from end of normal inspiration to the average breath‐hold level during simulation. RPM data was analyzed. Free‐breathing and breath‐hold scans were fused by matching the field borders, scar, excision cavity, and skin. All image fusions and contours were performed by one physician. Dose change was expressed as percent change from free‐breathing to breath‐hold. Mean doses to heart and LAD and V20 of the left lung were analyzed. Clinical parameters evaluated were breath‐hold level, patient age and BMI. Results: Using breath‐hold technique an average mean dose reduction was noted to heart and LAD of 61% and 69%, respectively. Average left lung V20 for free‐breathing and breath‐hold were 18% and 13%, respectively. Mean heart dose reduction correlated with both breath‐hold level (r = 0.50) and age (r = 0.55). Fair correlation was noted for LAD mean dose reduction and breath‐hold level (r = 0.47), but little correlation was found for BMI or age. Little or no correlation was found between average left lung V20 change and breath‐hold level, BMI or age. Conclusions: On average, all patients experienced a dose reduction to heart and LAD with breath‐hold. Good correlations were noted in mean heart dose reduction with breath‐hold level and age. This study indicates younger patients treated with breath‐hold typically achieved greater heart dose reduction and those with higher breath‐ hold levels demonstrated larger dose reduction to heart and LAD.

Proton Treatment of Peripheral Lymph Nodes in Breast Cancer

The treatment of peripheral lymph nodes in locally advanced breast cancer patients often entails increased dose to organs at risk (OARs). The goal of this study is to evaluate the potential advantages of using proton therapy in treating peripheral lymph nodes vs. 3-dimensional conformal radiotherapy (3D-CRT) for left sided breast cancer patients. Treatment plan comparison was performed on planning computed tomography of 7 consecutive left-sided breast cancer patients. Patients were immobilized in the supine position using a Vac Loc device and Wing Board. All photon plans used a 4-field, mono-isocenter technique. Wide tangents were used to cover the internal mammary nodes. In the matched proton-photon technique, a proton field covering the internal mammary nodes, supraclavicular nodes and level II and III axillary nodes was matched to the opposing tangent photon fields. The proton field was planned using forward-planned, double-scattered 3-dimensional proton therapy techniques. The breast and/or chest wall were adequately treated in both modalities. There was no significant difference in the coverage of supraclavicular nodes, level I or III axillary nodes. Protons improved the coverage of level II lymph nodes, with a mean D95 of 50 Gy compared to D95 of 37 Gy with 3D-CRT (p = 0.01). Protons also improved the mean D95 of internal mammary nodes to 51 Gy vs. 42 Gy with 3D-CRT (p = 0.01). When protons were used to cover the peripheral lymph nodes, there was a significant decrease in the dose to the heart and ipsilateral lung for all isodose levels. In comparing protons vs. 3D-CRT, the mean left lung dose was 2 Gy vs. 13 Gy (p = 0.01); left lung V20 was 24% vs. 38% (p = 0.01), left lung V5 was 42% vs. 84% (p = 0.01), respectively. The mean heart V20 was 0% using proton vs. 8% with 3D-CRT (p = 0.01). The use of protons also lowered the cardiac V5 from 44% to 2% (p = 0.01). There was no significant difference in the mean maximum skin dose, which were 53 Gy in 3D-CRT and 56 Gy with the use of a matched proton field. Proton treatment of peripheral lymph nodes improved dose coverage of the peripheral lymph nodes and decreased the dose to the heart and ipsilateral lung. The dosimetric advantages may improve local control of breast cancer and reduce late effects from radiation treatment.

Irradiation du sein gauche et risque cardiaque : bases pour une étude prospective

This study aims to investigate whether there are dosimetric advantages to using VMAT (Volumetric Modulated Arc Therapy) for left-sided chest-wall patients over the three-dimensional conformal field-in-field (FinF) technique.There is a lack of dosimetric studies dedicated for chest-wall patients. Potential dosimetric advantage could be obtained using VMAT due to complex geometry of PTVs (Planning Target Volumes) and OARs (Organs at Risk) in chest-wall and lymph nodes.VMAT and FinF plans were generated and evaluated based on DVHs (Dose Volume Histograms) for both PTVs and OARs for 22 left-sided chest-wall patients with involved regional nodes. PTV HIs (Homogeneity Indices) and CIs (Conformity Indices), and EUDs (Equivalent Uniform Doses) for PTVs and OARs were also evaluated for comparisons between VMAT and FinF.FinF planning met PTV criteria adequately in all cases except two. In these two cases, VMAT was able to meet PTV criteria adequately. VMAT demonstrated significant reduction in left lung V20 Gy in chest-wall patients compared to FinF plans. The volumes of the right lung and right breast receiving 5 Gy were much higher in VMAT than those in FinF for all patients.Compared to the FinF technique, there is a generally limited benefit using VMAT for left-sided chest-wall patients due to large low-dose-bath to OARs with insignificant improvement in PTV coverage. In case where FinF planning cannot meet dose constrains, VMAT provides a viable option. The use of VMAT planning over the FinF technique in chest-wall cancers should be carefully analyzed on an individual basis.

Postoperative Proton Radiotherapy for Localized and Locoregional Breast Cancer: Potential for Clinically Relevant Improvements?

To study the potential reduction of dose to organs at risk (OARs) with intensity-modulated proton radiotherapy (IMPT) compared with intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT) photon radiotherapy for left-sided breast cancer patients. Comparative treatment-planning was performed using planning computed tomography scans of 20 left-sided breast cancer patients. For each patient, three increasingly complex locoregional volumes (planning target volumes [PTVs]) were defined: whole breast (WB) or chest wall (CW) = (PTV1), WB/CW plus medial-supraclavicular (MSC), lateral-supraclavicular (LSC), and level III axillary (AxIII) nodes = (PTV2) and WB/CW+MSC+LSC+AxIII plus internal mammary chain = (PTV3). For each patient, 3D-CRT, IMRT, and IMPT plans were optimized for PTV coverage. Dose to OARs was compared while maintaining target coverage. All the techniques met the required PTV coverage except the 3D-CRT plans for PTV3-scenario. All 3D-CRT plans for PTV3 exceeded left-lung V20. IMPT vs. 3D-CRT: significant dose reductions were observed for all OARs using IMPT for all PTVs. IMPT vs. IMRT: For PTV2 and PTV3, low (V5) left lung and cardiac doses were reduced by a factor >2.5, and cardiac doses (V22.5) were by a factor of >20 lower with IMPT compared with IMRT. When complex-target irradiation is needed, 3D-CRT often compromises the target coverage and increases the dose to OARs; IMRT can provide better results but will increase the integral dose. The benefit of IMPT is based on improved target coverage and reduction of low doses to OARs, potentially reducing the risk of late-toxicity. These results indicate a potential role of proton-radiotherapy for extended locoregional irradiation in left breast cancer.

SU‐FF‐T‐98: Evaluation of RapidArc for Locoregional Radiotherapy of Left‐Sided Breast Cancer: Comparison with Conventional Intensity Modulated Radiotherapy(cIMRT)

Purpose: RapidArc is a novel volumetric modulated arc technique with dynamically variable MLC positions, dose rate and gantry speed. RapidArc is highly efficient and has the potential to reduce monitor units and treatment times compared to cIMRT. This report presents our first experience in performing treatment planning for breast cancer using Eclipse RapidArc optimization software 8.4.10 that supports multiple arcs. RapidArc plans were compared with cIMRT for locoregional radiotherapy of left‐sided breast cancer, including the internal mammary nodes (IMN). Method and Materials: 4 patients previously treated with cIMRT to the left breast/chest wall and regional nodes, including internal mammary chain, were planned (50Gy/25fractions) using the same contours and CT dataset with the RapidArc technique. Different RapidArc planning strategies were investigated. The endpoints of the comparison between RapidArc and cIMRT plans were breast PTV homogeneity, conformity of the plans, heart V30, left lung V20, mean doses to surrounding structures, number of monitor units (MUs) and treatment time. Results: 2 arcs were used due to the large treatment volumes to be optimized and the finite travel range of the multileaf collimator (MLC). Treatment plans generated using RapidArc optimization resulted in similar PTV homogeneity as compared with cIMRT. The best RapidArc plans (2 short arcs of 190 degrees each) reduced the mean dose to heart from 11.2±1.0Gy to 9.7±0.7Gy and ipsilateral lung from 14.5±0.8 to 13.6±0.6Gy. The number of MUs was reduced by 50% and the mean beam on time was reduced from 5.85±1.04 minutes to 1.4±0.05 minutes for RapidArc as compared with cIMRT. Conclusions: RapidArc optimization employing 2 arcs is feasible and yielded similar dosimetric plan quality as compared to cIMRT. RapidArc reduced the MUs and significantly reduced the beam on time as compared to cIMRT.

Comparison of conventional inserts and an add-on electron MLC for chest wall irradiation of left-sided breast cancer

Background. Collimation of irregularly shaped clinical electron beams is currently based on electron inserts made of low melting point alloys. The present investigation compares a conventional electron applicator with insert and add-on eMLC-based dose distributions in the postoperative chest wall irradiation of left-sided breast cancer. Material and methods. Voxel Monte Carlo++ (VMC++) calculated dose distributions related to electron fields were compared with 10 left-sided breast cancer patients after radical mastectomy. The prescription dose was 50 Gy at a build-up maximum. The same dose was prescribed for the ipsilateral axillary, parasternal and supraclavicular lymph nodes that were treated with photons and calculated with a pencil beam algorithm. The insert beams were shaped with 1.5 cm thick Wood's metal electron inserts in an electron applicator of a Varian 2100 C/D linac. Doses for the eMLC-shaped beams were calculated for an eMLC prototype with 2 cm thick and 5 mm wide steel leaves. The same collimator-to-surface distance (CSD) of 5.8 cm was used for both collimators. Results. The mean PTV dose was slightly higher for the eMLC plans (50.7 vs 49.5 Gy, p<0.001, respectively). The maximum doses assessed by D5% for the eMLC and insert were 60.9 and 59.1 Gy (p<0.001). The difference was due to the slightly higher doses near the field edges for the eMLC. The left lung V20 volumes were 34.5% and 34.0% (p<0.001). There was only a marginal difference in heart doses. Discussion: Despite a slight increase of maximum dose in PTV the add-on electron MLC for chest wall irradiation results in practically no differences in dose distributions compared with the present insert-based collimation.

Inverse-planned, dynamic, multi-beam, intensity-modulated radiation therapy (IMRT): A promising technique when target volume is the left breast and internal mammary lymph nodes

The purpose of this study was to determine the optimum beam number and orientation for inverse-planned, dynamic intensity-modulated radiation therapy (IMRT) for treatment of left-sided breast cancer and internal mammary nodes (IMNs) to improve target coverage while reducing cardiac and ipsilateral lung irradiation. Computed tomography (CT) data was used from 5 patients with left-sided breast cancer in whom the heart was close to the chest wall. The planning target volume (PTV) was the full breast plus ipsilateral IMNs. Two geometric beam arrangements were investigated, 240° and 190° sector angles, and the number of beams was increased from 7 to 9 to 11. Dose comparison metrics included: PTV homogeneity and conformity indices (HI, CI), heart V30, left lung V20, and mean doses to surrounding structures. To assess clinical application, the IMRT plans with 11 beams equally spaced in a 190° sector angle were compared to conventional plans. Treatment times were modeled. The 190° IMRT plans improved PTV HI and CI and reduced mean dose to the heart, lungs, contralateral breast, and total healthy tissue (all p < 0.05) compared to a 240° sector angle. The 11-beam plan significantly improved PTV HI and CI, heart V30, left lung V20, and healthy tissue V5 compared to a 7-beam plan (all p < 0.05). The 11-beam plan reduced heart V30 and left lung V20 ( p < 0.05) without compromising PTV coverage, compared to a 9-beam plan. Compared to a conventional plan, the IMRT class solution significantly improved PTV HI and CI (both p < 0.01), heart V30 ( p = 0.01), and marginally reduced left lung V20 ( p = 0.07) but increased contralateral breast and lung mean dose ( p < 0.001) and healthy tissue V5 ( p < 0.001). An 11-beam 190° sector angle IMRT technique as a class solution is clinically feasible.