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A Dosimetric Comparative Analysis of TomoDirect and Three-Dimensional Conformal Radiotherapy in Early Breast Cancer.

Chung MJ, Kim SH, Lee JH, Suh YJ - J Breast Cancer (2015)

Bottom Line: A total of 50.4 Gy in 28 fractions were prescribed to the planning target volume.The organs at risk (OAR) such as lung and heart were contoured.Compared to 3D-CRT, TomoDirect could result in favorable target coverage while reducing the irradiation dose of the ipsilateral lung for patients with early breast cancer.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, St. Vincent's Hospital, The Catholic University of Korea College of Medicine, Suwon, Korea.

ABSTRACT

Purpose: The purpose of this study is to compare dosimetric parameters of intensity-modulated mode of TomoDirect and three-dimensional conformal radiotherapy (3D-CRT) in patients with early breast cancer.

Methods: TomoDirect and 3D-CRT planning were carried out for 26 patients with early breast cancer who had received breast-conserving surgery. A total of 50.4 Gy in 28 fractions were prescribed to the planning target volume. The organs at risk (OAR) such as lung and heart were contoured. Planning target volume (PTV) dose coverage, radiation conformity index (RCI), radical dose homogeneity index (rDHI), and irradiation dose of organs at risk were compared between TomoDirect and 3D-CRT planning.

Results: The mean PTV dose (51.65±0.37 Gy) and V47.8 (100%) in TomoDirect were significantly higher than the mean PTV dose (50.88±0.65 Gy) and V47.8 (89.23%±0.06%) in 3D-CRT (all, p<0.001). The RCI value in TomoDirect was significantly better than that in 3D-CRT (1.00 vs. 1.13, p<0.001). However, the rDHI value in TomoDirect was not significantly better than that in 3D-CRT (0.72 vs. 0.67, p=0.056). The mean lung dose and V10, V20, V30, and V40 values of ipsilateral lung in TomoDirect were significantly lower than those in 3D-CRT (all, p<0.05). There is no significant difference in the V10, V20, V30, and V40 values of heart between TomoDirect and 3D-CRT. And the mean dose for heart in TomoDirect was marginally lower than that in 3D-CRT (1.05 Gy vs. 1.62 Gy, p=0.085). The mean dose for left anterior descending coronary artery in left breast cancer was significantly lower in TomoDirect than in 3D-CRT (7.2 Gy vs. 12.1 Gy, p<0.001).

Conclusion: Compared to 3D-CRT, TomoDirect could result in favorable target coverage while reducing the irradiation dose of the ipsilateral lung for patients with early breast cancer.

No MeSH data available.


Related in: MedlinePlus

Dose distribution for TomoDirect plan (A) and three-dimensional conformal radiotherapy plan (B). Red contour means the planning target volume which contains lumpectomy site with clips and normal breast tissue.
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Figure 1: Dose distribution for TomoDirect plan (A) and three-dimensional conformal radiotherapy plan (B). Red contour means the planning target volume which contains lumpectomy site with clips and normal breast tissue.

Mentions: Planning target volume (PTV) was defined using the contouring guideline of Radiation Therapy Oncology Group [9,10]. PTV included breast palpable tissue and the tumor bed. The heart was contoured according to the Taylor et al. [11]. The cranial limit of the heart included the right atrium and excluded the pulmonary trunk, ascending aorta and superior vena cava. The lowest contour of the heart was the caudal myocardial border. For IMRT-mode of TomoDirect plan, the field width, pitch, and modulation factor need to be selected. Then, the dose distribution for each beamlet that passes through the target is calculated by a convolution/superposition algorithm. Two tangential beams with a jaw size of 2.5 cm, a pitch of 0.25, and a modulation factor of 2.0 was set. A normal calculation grid of 0.356×0.356 cm2 was used in optimization and calculation processes. Beam angles were selected to minimize the dose to normal tissues and to avoid the irradiation to the contralateral breast (Figure 1A). A total of 50.4 Gy in 28 fractions with 6 MV photon were prescribed to the PTV in TomoDirect. The organ at risk (OAR) such as lung and heart was contoured. The goals of TomoDirect were as follows: (1) at least 95% of PTV received 100% of the prescribed dose; (2) more than 105% of the prescribed dose should be below 10% of PTV; (3) more than 110% of the prescribed dose should be below 5% of PTV; (4) mean irradiation dose of the lung should be under 10 Gy; (5) 20% of the lung was kept under 20 Gy; (6) 10% of the lung was kept under 30 Gy; (7) 10% of the heart was kept under 10 Gy; and (8) 5% of the heart was kept under 20 Gy. For 3D-CRT planning, two tangential fields with enhanced dynamic wedge were used. The same gantry angles were used for TomoDirect and 3D-CRT planning. Dynamic wedge and beam weighting were applied to optimize the coverage of the PTV while minimizing the exposure to the normal tissue. A total of 50.4 Gy in 28 fractions delivered with 6 to 15 MV photon was prescribed for the PTV in 3D-CRT. The isocenter was set at the half point between the mid-axilla and the anterior chest wall in the middle CT-slice of the PTV. The superior, inferior, and lateral border of the field was 1.5 cm apart from the contoured PTV without block. Medial border of the field was 1 cm apart from the PTV with a conventional block margin (Figure 1B).


A Dosimetric Comparative Analysis of TomoDirect and Three-Dimensional Conformal Radiotherapy in Early Breast Cancer.

Chung MJ, Kim SH, Lee JH, Suh YJ - J Breast Cancer (2015)

Dose distribution for TomoDirect plan (A) and three-dimensional conformal radiotherapy plan (B). Red contour means the planning target volume which contains lumpectomy site with clips and normal breast tissue.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4381124&req=5

Figure 1: Dose distribution for TomoDirect plan (A) and three-dimensional conformal radiotherapy plan (B). Red contour means the planning target volume which contains lumpectomy site with clips and normal breast tissue.
Mentions: Planning target volume (PTV) was defined using the contouring guideline of Radiation Therapy Oncology Group [9,10]. PTV included breast palpable tissue and the tumor bed. The heart was contoured according to the Taylor et al. [11]. The cranial limit of the heart included the right atrium and excluded the pulmonary trunk, ascending aorta and superior vena cava. The lowest contour of the heart was the caudal myocardial border. For IMRT-mode of TomoDirect plan, the field width, pitch, and modulation factor need to be selected. Then, the dose distribution for each beamlet that passes through the target is calculated by a convolution/superposition algorithm. Two tangential beams with a jaw size of 2.5 cm, a pitch of 0.25, and a modulation factor of 2.0 was set. A normal calculation grid of 0.356×0.356 cm2 was used in optimization and calculation processes. Beam angles were selected to minimize the dose to normal tissues and to avoid the irradiation to the contralateral breast (Figure 1A). A total of 50.4 Gy in 28 fractions with 6 MV photon were prescribed to the PTV in TomoDirect. The organ at risk (OAR) such as lung and heart was contoured. The goals of TomoDirect were as follows: (1) at least 95% of PTV received 100% of the prescribed dose; (2) more than 105% of the prescribed dose should be below 10% of PTV; (3) more than 110% of the prescribed dose should be below 5% of PTV; (4) mean irradiation dose of the lung should be under 10 Gy; (5) 20% of the lung was kept under 20 Gy; (6) 10% of the lung was kept under 30 Gy; (7) 10% of the heart was kept under 10 Gy; and (8) 5% of the heart was kept under 20 Gy. For 3D-CRT planning, two tangential fields with enhanced dynamic wedge were used. The same gantry angles were used for TomoDirect and 3D-CRT planning. Dynamic wedge and beam weighting were applied to optimize the coverage of the PTV while minimizing the exposure to the normal tissue. A total of 50.4 Gy in 28 fractions delivered with 6 to 15 MV photon was prescribed for the PTV in 3D-CRT. The isocenter was set at the half point between the mid-axilla and the anterior chest wall in the middle CT-slice of the PTV. The superior, inferior, and lateral border of the field was 1.5 cm apart from the contoured PTV without block. Medial border of the field was 1 cm apart from the PTV with a conventional block margin (Figure 1B).

Bottom Line: A total of 50.4 Gy in 28 fractions were prescribed to the planning target volume.The organs at risk (OAR) such as lung and heart were contoured.Compared to 3D-CRT, TomoDirect could result in favorable target coverage while reducing the irradiation dose of the ipsilateral lung for patients with early breast cancer.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, St. Vincent's Hospital, The Catholic University of Korea College of Medicine, Suwon, Korea.

ABSTRACT

Purpose: The purpose of this study is to compare dosimetric parameters of intensity-modulated mode of TomoDirect and three-dimensional conformal radiotherapy (3D-CRT) in patients with early breast cancer.

Methods: TomoDirect and 3D-CRT planning were carried out for 26 patients with early breast cancer who had received breast-conserving surgery. A total of 50.4 Gy in 28 fractions were prescribed to the planning target volume. The organs at risk (OAR) such as lung and heart were contoured. Planning target volume (PTV) dose coverage, radiation conformity index (RCI), radical dose homogeneity index (rDHI), and irradiation dose of organs at risk were compared between TomoDirect and 3D-CRT planning.

Results: The mean PTV dose (51.65±0.37 Gy) and V47.8 (100%) in TomoDirect were significantly higher than the mean PTV dose (50.88±0.65 Gy) and V47.8 (89.23%±0.06%) in 3D-CRT (all, p<0.001). The RCI value in TomoDirect was significantly better than that in 3D-CRT (1.00 vs. 1.13, p<0.001). However, the rDHI value in TomoDirect was not significantly better than that in 3D-CRT (0.72 vs. 0.67, p=0.056). The mean lung dose and V10, V20, V30, and V40 values of ipsilateral lung in TomoDirect were significantly lower than those in 3D-CRT (all, p<0.05). There is no significant difference in the V10, V20, V30, and V40 values of heart between TomoDirect and 3D-CRT. And the mean dose for heart in TomoDirect was marginally lower than that in 3D-CRT (1.05 Gy vs. 1.62 Gy, p=0.085). The mean dose for left anterior descending coronary artery in left breast cancer was significantly lower in TomoDirect than in 3D-CRT (7.2 Gy vs. 12.1 Gy, p<0.001).

Conclusion: Compared to 3D-CRT, TomoDirect could result in favorable target coverage while reducing the irradiation dose of the ipsilateral lung for patients with early breast cancer.

No MeSH data available.


Related in: MedlinePlus