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The Lateral Decubitus Breast Boost: Description, Rationale and Efficacy
Proceedings of the 50th Annual ASTRO Meeting define regional LN groups by CT. Lymphotrophic nanoparticle enhanced MRI (LN-MRI) allows for radiographic identification of LN containing metastasis and also allows visualization of normal regional lymphatics with high accuracy for patients with breast cancer. We seek to determine coverage of malignant and benign breast lymphatics as defined LN-MRI using standard RT fields based on bony anatomy and generally accepted CT nodal volumes. Materials/Methods: Twenty-three patients with pathologically confirmed breast cancer underwent MRI with and without Ferumoxtran-10 administration (Combidex; AMAG Pharmaceuticals, Cambridge, MA). The MRIs were anatomically registered to a reference CT scan and benign and malignant LN according to LN-MRI were contoured. Contoured nodes were resampled in the reference patient, replacing actual LN with 5 mm spherical "reference" LN employing a center-of-mass sampling algorithm to allow for a statistical analysis according to nodal position, removing patient specific bias resulting from variation in volumes. Standard RT fields including tangents, supraclavicular (SCV), and posterior axillary boost (PAB) were placed based on bony anatomy. SCV, level 1-3 LN, and internal mammary LN were contoured on CT. Fields and isodose lines were chosen without visualization of LN-MRI LN. Coverage and contribution of fields were assessed. Results: Eighty-one percent of all LN defined by LN-MRI were covered by the 45 Gy isodose line; 82% of malignant and 79% of benign. The 50 Gy isodose line encompassed only 60% of LN-MRI defined lymphatics; 64% of malignant and 59% benign. For nodal volumes contoured in the absence of a margin, only 70% of malignant LN and 71% of benign LN were within contoured volumes. However, when a 5 mm expansion was added, 95% of malignant LN and 96% of benign LN were included in this volume. Conclusions: An LN-MRI may be a useful tool for better delineating the location of the regional lymphatics for breast cancer patients. These results suggest a margin is advisable when defining nodal volumes by CT. The use of IMRT and trials examining the role of axillary RT in lieu of surgery makes accurately defining the location of breast regional lymphatics of paramount importance. Author Disclosure: S.M. MacDonald, None; M.G. Harisinghani, None; J. Wolfgang, None; B. Napolitano, None; A. Katkar, None; A.G. Taghian, None.
2006
The Lateral Decubitus Breast Boost: Description, Rationale and Efficacy
M. S. Ludwig, E. A. Strom, M. D. McNeese, G. H. Perkins, T. A. Buchholz M.D. Anderson Cancer Center, Houston, TX Purpose/Objective(s): To describe and evaluate a technique for breast irradiation - the lateral decubitus boost, used as a part of breast conservation radiotherapy. These patients undergo a second simulation for electron boost using enhanced body positioning to optimize the treatment anatomy and thus minimize the necessary depth of penetration for the electron beam. Materials/Methods: A total of 1,429 patients had two or more simulations for breast cancer at UT M.D. Anderson Cancer Center from January 1, 2000 to February 1, 2008. Of these, a total of 231 patients underwent resimulation in the lateral decubitus position with electron beams for their electron boost. The distance from the skin to the maximal depth of target volume was measured in both the original supine whole breast plan and boost plan in all patients. Patients who underwent whole breast treatment in the prone position were excluded. Age, BMI, electron energy used for the boost, skin reaction, and status at last follow-up were evaluated. The electron energy needed to cover the tumor bed by the distal 90% isodose line of the original plan depth was calculated using measured depth tables. Results: Resimulation in the lateral decubitus position reduced the distance from the skin to the maximal depth of target volume in all patients. The average distance from skin to depth of volume was 5.80 cm in the original plan, and 3.62 cm in the lateral decubitus plan, with an average reduction of 2.12 cm. A total of 154 (66.7%) of patients experienced no desquamation and only 14 patients (6%) experienced moist desquamation in the boost field at the end of treatment. If treated in the original position, 146 (63.2%) of the patients would not have the target volume covered by the distal 90% isodose line of the maximum electron energy available at our institution, 20 MeV. The average BMI of these patients was 30.4, which is considered obese. Repositioning of the patients allowed for an average reduction of electron energy of approximately 7 MeV. The median skin entrance dose was reduced from about 92.5% to about 85%. Conclusions: Repositioning and resimulation of selected patients into the lateral decubitus position for their breast boost allows for a decrease in the distance from the skin to the deepest area of the target volume. This allows for the improved electron coverage of the tumor bed while reducing the entrance dose to the skin and exit dose to the lung. The BMI was used in this study as a surrogate marker for breast volume. Patients with larger BMI have a greater distance from skin to depth on the original plan and a greater reduction in depth with repositioning. The low moist desquamation rate suggests that this is a well-tolerated boost regimen for a patient population with a high BMI, who would typically have a high risk for acute toxicity. Author Disclosure: M.S. Ludwig, None; E.A. Strom, None; M.D. McNeese, None; G.H. Perkins, None; T.A. Buchholz, None.
2007
Do We Overtreat or Undertreat the Axillary Region in Lymph Node-positive Breast Cancer Patients?
O. Karakoyun Celik1, S. Hoca2, Y. Bo¨lu¨kbas xı2, N. Olacak2, A. Haydaroglu2 1 Celal Bayar University, Faculty of Medicine, Department of Radiation Oncology, Manisa, Turkey, 2Ege University, Faculty of Medicine, Department of Radiation Oncology, Izmir, Turkey
Purpose/Objective(s): Adjuvant radiotherapy (RT) of supraclavicular (SC) and axillary apical (AA) lymph nodes is an accepted standard treatment in patients with multiple axillary lymph nodes. However, it has been shown that the location of both SC and AA lymph nodes can vary from patient to patient. In this study, we evaluated the axillary region doses of 35 patients who were virtually treated by standard anterior SC and posterior axillary boost (PAB) fields to 50 Gy with 6 MV photons. Materials/Methods: Thirty-five patients underwent computed tomography (CT) scanning in the supine treatment position and 5 mm axial images were obtained. Breast or chest wall volumes, axillary levels (AL) I, II, and III, and SC lymph node volumes were delineated and then standard SC and PAB field were developed on DRR images for each patient. The dose was prescribed to a tissue depth of 3 cm for SC, to the midaxillary depth for PAB field using 6 MV photon beams. All plans were set to 100% at the isocentre and the dose was prescribed to the 95% isodose. The depth for SC lymph nodes was measured from the isocenter of SC field and for ALs II and III lymph nodes, from the isocenter of PAB field in each patient. The volumes of ALs II and III that were out of the PAB
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2006
The Lateral Decubitus Breast Boost: Description, Rationale and Efficacy
M. S. Ludwig, E. A. Strom, M. D. McNeese, G. H. Perkins, T. A. Buchholz M.D. Anderson Cancer Center, Houston, TX Purpose/Objective(s): To describe and evaluate a technique for breast irradiation - the lateral decubitus boost, used as a part of breast conservation radiotherapy. These patients undergo a second simulation for electron boost using enhanced body positioning to optimize the treatment anatomy and thus minimize the necessary depth of penetration for the electron beam. Materials/Methods: A total of 1,429 patients had two or more simulations for breast cancer at UT M.D. Anderson Cancer Center from January 1, 2000 to February 1, 2008. Of these, a total of 231 patients underwent resimulation in the lateral decubitus position with electron beams for their electron boost. The distance from the skin to the maximal depth of target volume was measured in both the original supine whole breast plan and boost plan in all patients. Patients who underwent whole breast treatment in the prone position were excluded. Age, BMI, electron energy used for the boost, skin reaction, and status at last follow-up were evaluated. The electron energy needed to cover the tumor bed by the distal 90% isodose line of the original plan depth was calculated using measured depth tables. Results: Resimulation in the lateral decubitus position reduced the distance from the skin to the maximal depth of target volume in all patients. The average distance from skin to depth of volume was 5.80 cm in the original plan, and 3.62 cm in the lateral decubitus plan, with an average reduction of 2.12 cm. A total of 154 (66.7%) of patients experienced no desquamation and only 14 patients (6%) experienced moist desquamation in the boost field at the end of treatment. If treated in the original position, 146 (63.2%) of the patients would not have the target volume covered by the distal 90% isodose line of the maximum electron energy available at our institution, 20 MeV. The average BMI of these patients was 30.4, which is considered obese. Repositioning of the patients allowed for an average reduction of electron energy of approximately 7 MeV. The median skin entrance dose was reduced from about 92.5% to about 85%. Conclusions: Repositioning and resimulation of selected patients into the lateral decubitus position for their breast boost allows for a decrease in the distance from the skin to the deepest area of the target volume. This allows for the improved electron coverage of the tumor bed while reducing the entrance dose to the skin and exit dose to the lung. The BMI was used in this study as a surrogate marker for breast volume. Patients with larger BMI have a greater distance from skin to depth on the original plan and a greater reduction in depth with repositioning. The low moist desquamation rate suggests that this is a well-tolerated boost regimen for a patient population with a high BMI, who would typically have a high risk for acute toxicity. Author Disclosure: M.S. Ludwig, None; E.A. Strom, None; M.D. McNeese, None; G.H. Perkins, None; T.A. Buchholz, None.
2007
Do We Overtreat or Undertreat the Axillary Region in Lymph Node-positive Breast Cancer Patients?
O. Karakoyun Celik1, S. Hoca2, Y. Bo¨lu¨kbas xı2, N. Olacak2, A. Haydaroglu2 1 Celal Bayar University, Faculty of Medicine, Department of Radiation Oncology, Manisa, Turkey, 2Ege University, Faculty of Medicine, Department of Radiation Oncology, Izmir, Turkey
Purpose/Objective(s): Adjuvant radiotherapy (RT) of supraclavicular (SC) and axillary apical (AA) lymph nodes is an accepted standard treatment in patients with multiple axillary lymph nodes. However, it has been shown that the location of both SC and AA lymph nodes can vary from patient to patient. In this study, we evaluated the axillary region doses of 35 patients who were virtually treated by standard anterior SC and posterior axillary boost (PAB) fields to 50 Gy with 6 MV photons. Materials/Methods: Thirty-five patients underwent computed tomography (CT) scanning in the supine treatment position and 5 mm axial images were obtained. Breast or chest wall volumes, axillary levels (AL) I, II, and III, and SC lymph node volumes were delineated and then standard SC and PAB field were developed on DRR images for each patient. The dose was prescribed to a tissue depth of 3 cm for SC, to the midaxillary depth for PAB field using 6 MV photon beams. All plans were set to 100% at the isocentre and the dose was prescribed to the 95% isodose. The depth for SC lymph nodes was measured from the isocenter of SC field and for ALs II and III lymph nodes, from the isocenter of PAB field in each patient. The volumes of ALs II and III that were out of the PAB
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