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Factors Affecting Contralateral Breast Dose in Radiation Treatment of Breast Cancer
I. J. Radiation Oncology d Biology d Physics
S224
Volume 78, Number 3, Supplement, 2010
Materials/Methods: Recurrent or advanced breast cancer patients with contrasted CT images to cover the whole regional nodes at the time of recurrence or advanced disease staging prior to systemic therapy were eligible. The regional lymph nodes were categorized into 8 anatomical substructures: medial and lateral-supraclavicular(Sc-M, Sc-L); axilla (ALN)-I,II,III; infraclavicular (Ic); Rotter’s nodes (RN) and internal mammary nodes (IMN). Frequency of involvement and anatomical characteristics of the involved nodes on CT images were analyzed. Results: A total of 97 regional recurrent pts and 14 advanced breast cancer pts with eligible images from July 2003 to January 2009 entered current study. Within the 111 pts, 199 anatomical substructures of involved nodes were identified. The frequency of involvement includes: Sc-M: 33 (16.6%), Sc-L:21 (10.6%), ALN-I: 30 (15.1%), ALN-II: 25 (12.6%), ALN-III and Ic: 35 (17.6%), RN: 27 (13.6%), IMN: 28 (14.1%). In pts received prior axillary dissection, 67.0% (114/170) had recurrent nodes cranial to the axillary vein. With IMN involvement, 26/28 had nodes within the first 3 intercostal spaces. The average distance between the center of involved IMN and midline is 29.38 ± 6.7 mm. The average distance between the center of involved IMN and internal mammary vessels (IMV) are 6.19 ± 5.73 mm in lateral and 5.73 ± 4.56 mm in depth. The average maximum depth of involved Sc nodes is 53.19 ± 21.68 mm. Conclusions: Identification of involved regional nodes in recurrent and advanced breast cancer is beneficial for better understanding the distribution of risk area. The lymphatic structures observed in our series confirm that current target definition of regional nodes is consistent with the potential risk of regional lymphatic spread. Sc and axillary nodes cranial to the axillary vein should be considered the primary risk target as it accounts for 2/3 of the recurrent nodes. The anatomical relationship of IMN and IMV supports the use of IMV as reference in IMN delineation and 7-10 mm from the center of IMV should be regarded as adequate definition of CTV to IMN. Conventional field design is unlikely to provide sufficient dose to the entire risk region. Individual treatment planning would become feasible with increasing knowledge of natural risk of nodal involvement. Author Disclosure: J. Chen, None; C. Zhu, None; J. Chen, None; G. Cai, None; J. Ma, None; X. Guo, None.
2043
Factors Affecting Contralateral Breast Dose in Radiation Treatment of Breast Cancer
I. J. Das, E. Yang, S. Bednar, M. Ewing, K. Hutchins, M. Cao, P. A. S. Johnstone, J. Z. Andrews Indiana University School of Medicine, Indianapolis, IN Purpose/Objective(s): Contralateral breast (CLB) dose is a serious concern in the management of the breast cancer especially for young and in some patient population with increased co-morbidity for second neoplasm. Factors and techniques that could affect CLB dose were retrospectively investigated. Materials/Methods: This investigation evaluated the modern radiation treatments; forward and inverse dose planning in conventional field-in-field (FIF) or intensity modulated radiation therapy (IMRT) in 35 breast patients recently treated at our institution. There were 26 and 9 patients in FIF and IMRT technique, respectively. The ipsilateral breast and CLB were contoured based on the RTOG Protocol-0413 guidelines sparing 2 mm of skin and without lung. Organs at risk (OAR) included; lung, heart, thyroid and liver. Treatment planning was performed with CT data using Eclipse treatment planning system with analytical anisotropic algorithm (AAA) with inhomogeneity correction in dose calculation. For conventional treatment, a FIF technique was used. For IMRT, 7-9 fields were used and optimized to produce a uniform dose distribution. The dose uniformity was maintained to # 10% hotspot by choosing beam energy (6-5 MV), beam weight and number of FIF. Breast parameters; chest wall separation (CWS), central lung distance (CLD), body weight along with dosimetric information were collected. The mean and maximum dose receiving at least 1 cm3 tissue volume of the CLB was acquired. Results: The chest wall separation ranged from 16-29 cm with an average of 22 ± 3.2 cm. The mean treated breast and CLB volume were 1465 ± 703 cm3 and 1346 ± 698 cm3 in FIF and corresponding values in IMRT were 1384 ± 785 cm3 and 1552 ± 697 cm3, respectively. In IMRT, unlike FIF, where the hotspot in the treated breast increases with CWS, there is no correlation, possibly due to optimization. The CLB dose was mainly concentrated in the vicinity of the inner quadrant, and the max dose was evaluated. In FIF, the CLB max dose was weakly correlated with CLD and CLB volume and ranged between 8-21% of the prescribed dose (13.4 ± 4%) and the mean dose was \2%. In IMRT, CLB max dose was significantly higher ranging 9-23% (17 ± 5%) and mean dose \5% in IMRT. The monitor units delivered for IMRT was nearly 4.5 times higher (1066 ± 108) compared to 236 ± 50 in FIF. Conclusions: The CLB dose is weakly correlated with breast volume and CLD in FIF but not in IMRT. Other breast parameters did not correlate with the max dose in CLB. IMRT delivered a significantly higher CLB dose. Since IMRT required nearly 4.5 higher monitor unit and delivered a higher CLB max dose compared to FIF it should be used selectively and the risk and benefit of sparing OAR dose should be critically evaluated. Author Disclosure: I.J. Das, None; E. Yang, None; S. Bednar, None; M. Ewing, None; K. Hutchins, None; M. Cao, None; P.A.S. Johnstone, None; J.Z. Andrews, None.
2044
Interstitial High Dose Rate (HDR) Brachytherapy for Breast Cancer in Women # 50 Years of Age Compared to . 50 Years of Age: A Report of 264 Cases using Multi-catheter Technique
S. Haro1, R. J. Mark1,2, P. J. Anderson1, R. S. Akins1, M. Nair1 1
Joe Arrington Cancer Center, Lubbock, TX, 2Texas Tech University, Lubbock, TX
Purpose/Objective(s): The American College of Radiology does not have an age limit for breast conservation candidacy. Recent data indicates that Interstitial Implant and High Dose Rate (HDR) radiation afterloading compares very favorably to EBRT in early stage breast cancer. There is controversy regarding the use of HDR in patients # 50 years of age. We present our data in patients # 50 years of age compared to . 50 years of age. Materials/Methods: Patients with Tis, T1, and T2 tumors measuring # 4 cm, negative surgical margins, and 1-3 positive axillary lymph nodes were judged to be candidates for Interstitial Implant. Implants were performed under Stereotactic Mammographic guidance with conscious sedation and local anesthesia. The implants were placed with a custom designed template using from 3 to 8 planes, and 8 to 74 needles. Catheters were subsequently threaded thru the needles, and the needles removed. Catheter
S224
Volume 78, Number 3, Supplement, 2010
Materials/Methods: Recurrent or advanced breast cancer patients with contrasted CT images to cover the whole regional nodes at the time of recurrence or advanced disease staging prior to systemic therapy were eligible. The regional lymph nodes were categorized into 8 anatomical substructures: medial and lateral-supraclavicular(Sc-M, Sc-L); axilla (ALN)-I,II,III; infraclavicular (Ic); Rotter’s nodes (RN) and internal mammary nodes (IMN). Frequency of involvement and anatomical characteristics of the involved nodes on CT images were analyzed. Results: A total of 97 regional recurrent pts and 14 advanced breast cancer pts with eligible images from July 2003 to January 2009 entered current study. Within the 111 pts, 199 anatomical substructures of involved nodes were identified. The frequency of involvement includes: Sc-M: 33 (16.6%), Sc-L:21 (10.6%), ALN-I: 30 (15.1%), ALN-II: 25 (12.6%), ALN-III and Ic: 35 (17.6%), RN: 27 (13.6%), IMN: 28 (14.1%). In pts received prior axillary dissection, 67.0% (114/170) had recurrent nodes cranial to the axillary vein. With IMN involvement, 26/28 had nodes within the first 3 intercostal spaces. The average distance between the center of involved IMN and midline is 29.38 ± 6.7 mm. The average distance between the center of involved IMN and internal mammary vessels (IMV) are 6.19 ± 5.73 mm in lateral and 5.73 ± 4.56 mm in depth. The average maximum depth of involved Sc nodes is 53.19 ± 21.68 mm. Conclusions: Identification of involved regional nodes in recurrent and advanced breast cancer is beneficial for better understanding the distribution of risk area. The lymphatic structures observed in our series confirm that current target definition of regional nodes is consistent with the potential risk of regional lymphatic spread. Sc and axillary nodes cranial to the axillary vein should be considered the primary risk target as it accounts for 2/3 of the recurrent nodes. The anatomical relationship of IMN and IMV supports the use of IMV as reference in IMN delineation and 7-10 mm from the center of IMV should be regarded as adequate definition of CTV to IMN. Conventional field design is unlikely to provide sufficient dose to the entire risk region. Individual treatment planning would become feasible with increasing knowledge of natural risk of nodal involvement. Author Disclosure: J. Chen, None; C. Zhu, None; J. Chen, None; G. Cai, None; J. Ma, None; X. Guo, None.
2043
Factors Affecting Contralateral Breast Dose in Radiation Treatment of Breast Cancer
I. J. Das, E. Yang, S. Bednar, M. Ewing, K. Hutchins, M. Cao, P. A. S. Johnstone, J. Z. Andrews Indiana University School of Medicine, Indianapolis, IN Purpose/Objective(s): Contralateral breast (CLB) dose is a serious concern in the management of the breast cancer especially for young and in some patient population with increased co-morbidity for second neoplasm. Factors and techniques that could affect CLB dose were retrospectively investigated. Materials/Methods: This investigation evaluated the modern radiation treatments; forward and inverse dose planning in conventional field-in-field (FIF) or intensity modulated radiation therapy (IMRT) in 35 breast patients recently treated at our institution. There were 26 and 9 patients in FIF and IMRT technique, respectively. The ipsilateral breast and CLB were contoured based on the RTOG Protocol-0413 guidelines sparing 2 mm of skin and without lung. Organs at risk (OAR) included; lung, heart, thyroid and liver. Treatment planning was performed with CT data using Eclipse treatment planning system with analytical anisotropic algorithm (AAA) with inhomogeneity correction in dose calculation. For conventional treatment, a FIF technique was used. For IMRT, 7-9 fields were used and optimized to produce a uniform dose distribution. The dose uniformity was maintained to # 10% hotspot by choosing beam energy (6-5 MV), beam weight and number of FIF. Breast parameters; chest wall separation (CWS), central lung distance (CLD), body weight along with dosimetric information were collected. The mean and maximum dose receiving at least 1 cm3 tissue volume of the CLB was acquired. Results: The chest wall separation ranged from 16-29 cm with an average of 22 ± 3.2 cm. The mean treated breast and CLB volume were 1465 ± 703 cm3 and 1346 ± 698 cm3 in FIF and corresponding values in IMRT were 1384 ± 785 cm3 and 1552 ± 697 cm3, respectively. In IMRT, unlike FIF, where the hotspot in the treated breast increases with CWS, there is no correlation, possibly due to optimization. The CLB dose was mainly concentrated in the vicinity of the inner quadrant, and the max dose was evaluated. In FIF, the CLB max dose was weakly correlated with CLD and CLB volume and ranged between 8-21% of the prescribed dose (13.4 ± 4%) and the mean dose was \2%. In IMRT, CLB max dose was significantly higher ranging 9-23% (17 ± 5%) and mean dose \5% in IMRT. The monitor units delivered for IMRT was nearly 4.5 times higher (1066 ± 108) compared to 236 ± 50 in FIF. Conclusions: The CLB dose is weakly correlated with breast volume and CLD in FIF but not in IMRT. Other breast parameters did not correlate with the max dose in CLB. IMRT delivered a significantly higher CLB dose. Since IMRT required nearly 4.5 higher monitor unit and delivered a higher CLB max dose compared to FIF it should be used selectively and the risk and benefit of sparing OAR dose should be critically evaluated. Author Disclosure: I.J. Das, None; E. Yang, None; S. Bednar, None; M. Ewing, None; K. Hutchins, None; M. Cao, None; P.A.S. Johnstone, None; J.Z. Andrews, None.
2044
Interstitial High Dose Rate (HDR) Brachytherapy for Breast Cancer in Women # 50 Years of Age Compared to . 50 Years of Age: A Report of 264 Cases using Multi-catheter Technique
S. Haro1, R. J. Mark1,2, P. J. Anderson1, R. S. Akins1, M. Nair1 1
Joe Arrington Cancer Center, Lubbock, TX, 2Texas Tech University, Lubbock, TX
Purpose/Objective(s): The American College of Radiology does not have an age limit for breast conservation candidacy. Recent data indicates that Interstitial Implant and High Dose Rate (HDR) radiation afterloading compares very favorably to EBRT in early stage breast cancer. There is controversy regarding the use of HDR in patients # 50 years of age. We present our data in patients # 50 years of age compared to . 50 years of age. Materials/Methods: Patients with Tis, T1, and T2 tumors measuring # 4 cm, negative surgical margins, and 1-3 positive axillary lymph nodes were judged to be candidates for Interstitial Implant. Implants were performed under Stereotactic Mammographic guidance with conscious sedation and local anesthesia. The implants were placed with a custom designed template using from 3 to 8 planes, and 8 to 74 needles. Catheters were subsequently threaded thru the needles, and the needles removed. Catheter