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A comparative dosimetric study of left sided breast cancer after breast-conserving surgery treated with VMAT and IMRT.

ABSTRACT: BACKGROUND AND PURPOSES:This study compared VMAT and IMRT plans for intact breast radiotherapy for left sided breast cancer and evaluated the irradiated dose of planning target volume and OARs, especially focusing on heart and coronary artery. MATERIALS AND METHODS:Eleven patients with left sided breast cancer whose breast was relatively smaller (the mean volumes is 296 cc) treated with breast-conserving surgery were prescribed radiotherapy of 50 Gy in 25 fractions using two or four-field step and shoot IMRT (2 or 4-F IMRT), and one or two-arc VMAT (1 or 2-arc VMAT). The 10 Gy electron boost to the tumor bed after delivery of 50 Gy was not included in the analysis. Multiple planning parameters for the PTV and the PRV-OARs were measured and analyzed. RESULTS:Treatment plans generated using VMAT had better PTV homogeneity than the IMRT plans. For the PRV-OARs, the 1-arc VMAT had significantly higher Dmean and V5 for left lung and heart, and showed worse Dmean for liver, esophagus, spinal cord, contralateral lung and breast. In contrast, the 2-arc VMAT and the 2-F or 4-F IMRT plans showed better results for the PRV-OARs than the 1-arc VMAT. However, for the heart and coronary artery, the 1-arc VMAT showed better V20 and V40 compared with the other plans. Moreover, the 2 F-IMRT had specially advantage on V5 and V20 for heart and V5 for coronary arteries, the 2-F IMRT also showed a greater MU and treatment times. Using the table of quality score to evaluate the plans, we found that 2-F IMRT had the highest scores of 13, followed by the 2-arc VMAT plan (10 points) and 1-arc VMAT plan (8 points), and finally the 4-F IMRT plan (6 points). Moreover, when a dose comparison for heart minus coronary artery was calculated, the V20 and V40 for the rest of heart in all plans were very small and closed, indicating the dose to the coronary artery contributed dramatically to the high dose volumes for the entire heart. CONCLUSIONS:Compared to other plans, the 2-F IMRT plan with fewer monitor units and shorter delivery time is an appropriate technique for left sided breast cancer, which achieved good PTV coverage and sparing of organs at risk besides for the heart and coronary artery.

SUBMITTER: Zhao H

PROVIDER: S-EPMC4650319 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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A comparative dosimetric study of left sided breast cancer after breast-conserving surgery treated with VMAT and IMRT.

Zhao Hongfu H He Mingyuan M Cheng Guanghui G Han Dongmei D Wu Ning N Shi Dan D Zhao Zhipeng Z Jin Jianxue J

Radiation oncology (London, England) 20151117

<h4>Background and purposes</h4>This study compared VMAT and IMRT plans for intact breast radiotherapy for left sided breast cancer and evaluated the irradiated dose of planning target volume and OARs, especially focusing on heart and coronary artery.<h4>Materials and methods</h4>Eleven patients with left sided breast cancer whose breast was relatively smaller (the mean volumes is 296 cc) treated with breast-conserving surgery were prescribed radiotherapy of 50 Gy in 25 fractions using two or fo ...[more]

PMID: 26577189

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Project description:BackgroundBefore generating radiotherapy plans for breast cancer patients, the choice of plan techniques (three-dimensional conformal radiation therapy (3D-CRT) and volumetric modulated arc therapy (VMAT)) should be made. This study investigated the performance of two geometric indices in aiding the choice of 3D-CRT and VMAT plans in women undergoing left-sided whole breast radiotherapy.Materials and methods119 patients, previously treated with left-sided breast radiotherapy (61 3D-CRT treatments and 58 VMAT treatments) from a single institution, were retrospectively studied. Two geometric indices, which were cardiac junction (CJ) index and pulmonary junction (PJ) index, were defined and the relationship between these indices and dose of organs at risk (OARs) were evaluated. Two-tailed Student's t-test was performed to compare patient characteristics between 3D-CRT and VMAT. Linear regressions were calculated to investigate the association between geometric indices and absorbed dose of heart and left lung, including mean dose of heart (MHD), V5, V30 of heart, and mean dose of left lung (MLLD), V5, V10, V20, V30, V40 of left lung.ResultsThe CJ index was strongly correlated with the MHD in 3D-CRT group and VMAT group. The linear regression formulas were MHD = 4826.59 ×CJ Index+310.48 (R = 0.857, F = 163.77, P = 0.000) in 3D-CRT plans and MHD = 1789.29×CJ Index+437.50 (R = 0.45, F = 14.23, P = 0.000) in VMAT plans. The intersection of the two formulas was CJ index = 4.2% and MHD = 512.33 cGy. The PJ index demonstrated a strongly positive correlation with MLLD in 3D-CRT group and VMAT group as well. The linear regression formulas were MLLD = 2879.54×PJ Index+999.79 (R = 0.697, F = 55.86, P = 0.000) in 3D-CRT plans and MLLD = 1411.79×PJ Index+1091.88 (R = 0.676, F = 47.11, P = 0.000) in VMAT plans, the intersection of the two formulas was PJ index = 6.3% and MLLD = 1180.46 cGy.ConclusionsCJ index and PJ index could be used as a practical tool to select 3D-CRT or VMAT before generating plans. We recommend that VMAT plan is preferable when CJ index is greater than 4.2% and/or PJ index is greater than 14.6%, while 3D-CRT plan is the first choice in the opposite.

Project description:Volumetric-modulated arc therapy (VMAT) is emerging as a leading technology in treating early-stage, non-small cell lung cancer (NSCLC) with stereotactic ablative radiotherapy (SABR). However, two other modalities capable of deliver-ing intensity-modulated radiation therapy (IMRT) include fixed-beam and helical TomoTherapy (HT). This study aims to provide an extensive dosimetric compari-son among these various IMRT techniques for treating early-stage NSCLC with SABR. Ten early-stage NSCLC patients were retrospectively optimized using three fixed-beam techniques via nine to eleven beams (high and low modulation step-and-shoot (SS), and sliding window (SW)), two VMAT techniques via two partial arcs (SmartArc (SA) and RapidArc (RA)), and three HT techniques via three different fan beam widths (1 cm, 2.5 cm, and 5 cm) for 80 plans total. Fixed-beam and VMAT plans were generated using flattening filter-free beams. SS and SA, HT treatment plans, and SW and RA were optimized using Pinnacle v9.1, Tomoplan v.3.1.1, and Eclipse (Acuros XB v11.3 algorithm), respectively. Dose-volume histogram statistics, dose conformality, and treatment delivery efficiency were analyzed. VMAT treatment plans achieved significantly lower values for contralat-eral lung V5Gy (p ? 0.05) compared to the HT plans, and significantly lower mean lung dose (p < 0.006) compared to HT 5 cm treatment plans. In the comparison between the VMAT techniques, a significant reduction in the total monitor units (p = 0.05) was found in the SA plans, while a significant decrease was observed in the dose falloff parameter, D2cm, (p = 0.05), for the RA treatments. The maximum cord dose was significantly reduced (p = 0.017) in grouped RA&SA plans com-pared to SS. Estimated treatment time was significantly higher for HT and fixed-beam plans compared to RA&SA (p < 0.001). Although, a significant difference was not observed in the RA vs. SA (p = 0.393). RA&SA outperformed HT in all parameters measured. Despite an increase in dose to the heart and bronchus, this study demonstrates that VMAT is dosimetrically advantageous in treating early-stage NSCLC with SABR compared to fixed-beam, while providing significantly shorter treatment times.

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A comparative dosimetric study of left sided breast cancer after breast-conserving surgery treated with VMAT and IMRT.

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A comparative dosimetric study of left sided breast cancer after breast-conserving surgery treated with VMAT and IMRT.

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