Is There Justification for the Utilization of IMRT in the Treatment of Early-Stage Right Breast Cancer?

Purpose/Objective(s)Intensity Modulated Radiation Therapy (IMRT) has been shown to reduce the heart dose in adjuvant radiation therapy for left breast cancer. However, the benefit of IMRT for right breast cancer has not been established and is therefore not routinely employed in clinical practice. The purpose of this study is to (1) compare dosimetric parameters in women with early stage right breast cancer undergoing whole breast radiation therapy using 3-dimensional conformal radiation (3DCRT) versus intensity modulated radiation therapy (IMRT) and (2) determine treatment planning and/or anatomical correlates for patients that may benefit from IMRT.Materials/MethodsAn IMRT plan versus 3DCRT treatment plan comparison was performed for 20 consecutive female patients with early stage (T1-T2 N0M0) right breast cancer treated at our center from January 2012 to December 2012. The planned target volume (PTV) was contoured according to the RTOG atlas and guidelines. PTV was prescribed to 46.8-50.4 Gy in 26-28 fractions with PTV coverage goal of ≥95% receiving the prescription dose. The dosimetric parameters: percent total lung receiving 20 Gy (lung V20), maximum breast dose (Dmax), maximum skin dose (Dmax skin), as well as chest wall separation (CWS), and medial gantry angle (MGA) were determined for each paired treatment plan. Wilcoxon-signed rank test was performed to determine differences between IMRT and 3DCRT dosimetric parameters. Univariate analysis was used to identify planning or anatomic correlates with favorable dosimetric outcomes.ResultsThe total lung V20 Gy for IMRT (10.86 ± 2.81%) was significantly lower than for 3DCRT (12.92 ± 3.45%; p < 0.043). IMRT significantly reduced Dmax to 53.79 ± 2.17 Gy from 56.7 ± 2.24 Gy with 3DCRT (p 0.001). The 3DCRT yielded significantly higher Dmax skin (33.47 ± 3.21 Gy) than IMRT (24.16 ± 2.65 Gy; p < 0.0001). The mean CWS and MGA were 22.4 ± 2.6 cm and 126 ± 5.1°, respectively. There was a significant association between CWS and Dmax for 3DCRT (p < 0.026). However, there was no significant impact of CWS or MGA on either lung V20 or Dmax skin.ConclusionsAlthough IMRT is widely employed for left-sided breast cancers, there may be some utility for IMRT in the treatment of right breast cancer. Results reported herein demonstrate that the most significant positive impact of IMRT for right breast cancer is the reduction of Dmax and Dmax skin, with a more tempered advantage in the reduction of lung V20. Reduction of maximum breast and skin dose may harbor clinical relevance as it relates to acute skin toxicity, treatment interruptions as well as long-term fibrosis and adverse cosmetic outcomes. Chest wall separation may be a potential planning surrogate marker to determine which right-sided breast cancer patients may benefit from IMRT. Purpose/Objective(s)Intensity Modulated Radiation Therapy (IMRT) has been shown to reduce the heart dose in adjuvant radiation therapy for left breast cancer. However, the benefit of IMRT for right breast cancer has not been established and is therefore not routinely employed in clinical practice. The purpose of this study is to (1) compare dosimetric parameters in women with early stage right breast cancer undergoing whole breast radiation therapy using 3-dimensional conformal radiation (3DCRT) versus intensity modulated radiation therapy (IMRT) and (2) determine treatment planning and/or anatomical correlates for patients that may benefit from IMRT. Intensity Modulated Radiation Therapy (IMRT) has been shown to reduce the heart dose in adjuvant radiation therapy for left breast cancer. However, the benefit of IMRT for right breast cancer has not been established and is therefore not routinely employed in clinical practice. The purpose of this study is to (1) compare dosimetric parameters in women with early stage right breast cancer undergoing whole breast radiation therapy using 3-dimensional conformal radiation (3DCRT) versus intensity modulated radiation therapy (IMRT) and (2) determine treatment planning and/or anatomical correlates for patients that may benefit from IMRT. Materials/MethodsAn IMRT plan versus 3DCRT treatment plan comparison was performed for 20 consecutive female patients with early stage (T1-T2 N0M0) right breast cancer treated at our center from January 2012 to December 2012. The planned target volume (PTV) was contoured according to the RTOG atlas and guidelines. PTV was prescribed to 46.8-50.4 Gy in 26-28 fractions with PTV coverage goal of ≥95% receiving the prescription dose. The dosimetric parameters: percent total lung receiving 20 Gy (lung V20), maximum breast dose (Dmax), maximum skin dose (Dmax skin), as well as chest wall separation (CWS), and medial gantry angle (MGA) were determined for each paired treatment plan. Wilcoxon-signed rank test was performed to determine differences between IMRT and 3DCRT dosimetric parameters. Univariate analysis was used to identify planning or anatomic correlates with favorable dosimetric outcomes. An IMRT plan versus 3DCRT treatment plan comparison was performed for 20 consecutive female patients with early stage (T1-T2 N0M0) right breast cancer treated at our center from January 2012 to December 2012. The planned target volume (PTV) was contoured according to the RTOG atlas and guidelines. PTV was prescribed to 46.8-50.4 Gy in 26-28 fractions with PTV coverage goal of ≥95% receiving the prescription dose. The dosimetric parameters: percent total lung receiving 20 Gy (lung V20), maximum breast dose (Dmax), maximum skin dose (Dmax skin), as well as chest wall separation (CWS), and medial gantry angle (MGA) were determined for each paired treatment plan. Wilcoxon-signed rank test was performed to determine differences between IMRT and 3DCRT dosimetric parameters. Univariate analysis was used to identify planning or anatomic correlates with favorable dosimetric outcomes. ResultsThe total lung V20 Gy for IMRT (10.86 ± 2.81%) was significantly lower than for 3DCRT (12.92 ± 3.45%; p < 0.043). IMRT significantly reduced Dmax to 53.79 ± 2.17 Gy from 56.7 ± 2.24 Gy with 3DCRT (p 0.001). The 3DCRT yielded significantly higher Dmax skin (33.47 ± 3.21 Gy) than IMRT (24.16 ± 2.65 Gy; p < 0.0001). The mean CWS and MGA were 22.4 ± 2.6 cm and 126 ± 5.1°, respectively. There was a significant association between CWS and Dmax for 3DCRT (p < 0.026). However, there was no significant impact of CWS or MGA on either lung V20 or Dmax skin. The total lung V20 Gy for IMRT (10.86 ± 2.81%) was significantly lower than for 3DCRT (12.92 ± 3.45%; p < 0.043). IMRT significantly reduced Dmax to 53.79 ± 2.17 Gy from 56.7 ± 2.24 Gy with 3DCRT (p 0.001). The 3DCRT yielded significantly higher Dmax skin (33.47 ± 3.21 Gy) than IMRT (24.16 ± 2.65 Gy; p < 0.0001). The mean CWS and MGA were 22.4 ± 2.6 cm and 126 ± 5.1°, respectively. There was a significant association between CWS and Dmax for 3DCRT (p < 0.026). However, there was no significant impact of CWS or MGA on either lung V20 or Dmax skin. ConclusionsAlthough IMRT is widely employed for left-sided breast cancers, there may be some utility for IMRT in the treatment of right breast cancer. Results reported herein demonstrate that the most significant positive impact of IMRT for right breast cancer is the reduction of Dmax and Dmax skin, with a more tempered advantage in the reduction of lung V20. Reduction of maximum breast and skin dose may harbor clinical relevance as it relates to acute skin toxicity, treatment interruptions as well as long-term fibrosis and adverse cosmetic outcomes. Chest wall separation may be a potential planning surrogate marker to determine which right-sided breast cancer patients may benefit from IMRT. Although IMRT is widely employed for left-sided breast cancers, there may be some utility for IMRT in the treatment of right breast cancer. Results reported herein demonstrate that the most significant positive impact of IMRT for right breast cancer is the reduction of Dmax and Dmax skin, with a more tempered advantage in the reduction of lung V20. Reduction of maximum breast and skin dose may harbor clinical relevance as it relates to acute skin toxicity, treatment interruptions as well as long-term fibrosis and adverse cosmetic outcomes. Chest wall separation may be a potential planning surrogate marker to determine which right-sided breast cancer patients may benefit from IMRT.