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Breast Boost Using Non-Invasive Image-Guided Breast Brachytherapy Vs. En Face Electrons: A 2:1 Matched-Pair Analysis
Abstracts / Brachytherapy 12 (2013) S11eS77 scans during treatment. Daily variances in terms of balloon size (Vballoon), skin-to-balloon distance (Dskin) and skin-to-rib distance (Drib) were evaluated for each scan compared with reference scan. Total length of each catheter was measured for each fraction (total 60). By applying the reference plan to each daily CT image, dose variations to PTV, tumor bed, skin, and rib were evaluated with and without daily catheter length correction. Results: In the study, 17% of the treatment CT images had a Vballoon change more than 0.5 cm3. Dskin and Drib varied by more than 5 mm in 20% and 30% of treatment CTs, respectively. 17% of treatment fractions had a catheter length change of more than 2 mm. 10% of the skin and 13% of the rib received more than 125% prescription dose due to the change above. Without catheter length correction, 3% of V95 (% volume of PTV received 95% prescribed dose) had more than 2% coverage degradation, 10% of V150 (volume of PTV received 150% prescribed dose) increased by more than 3 cm3 and 17% of V200 (volume of PTV received 200% prescribed dose) increased by more than 2 cm3. Degradation of V95 is weakly correlated with Vballoon, Dskin, Drib and the original V95 (-0.1, 0.15, 0.15 and 0.12, respectively). With catheter length correction, 32% of V95 had more than 2% coverage degradation, 12% of V150 increased by more than 3 cm3 and 28% of V200 increased by more than 2 cm3. Degradation of V95 is strongly correlated with Vballoon, Drib and original V95 (-0.54, -0.28 and 0.47, respectively). Conclusions: Overall, APBI treatment with ConturaÒ balloon did not vary significantly from day to day. However, minor variation of daily treatment uncertainties can still degrade tumor bed coverage from acceptable (V95O90%) to unacceptable, especially when the reference plan is in the board line of acceptable coverage.
PD24 Low Rate of Mastectomy following Accelerated Partial Breast Irradiation Using Balloon-Based Brachytherapy J. Ben Wilkinson, MD1, Peter Y. Chen, MD1, Michelle Wallace, RN1, Ashley Fowler, BS1, M. Saada Jawad, MD1, Mark Sittig, BA2, Hong Ye, MS1, Donald Brabbins, MD1, Inga S. Grills, MD1. 1Radiation Oncology, William Beaumont Hospital, Royal Oak, MI; 2Tulane University School of Medicine, New Orleans, LA. Purpose: To evaluate rate of ipsilateral mastectomy and clinical outcomes at five years following accelerated partial breast irradiation (APBI) using balloon-based brachytherapy (BBB) at a single institution. Materials and Methods: An IRB-approved retrospective analysis of women treated with APBI using balloon-based brachytherapy with at least one year of followup was conducted to determine the rate of ipsilateral mastectomy at five years after completion of treatment. 268 patients were identified and eligible for this analysis with followup complete through September 2012. Adjuvant radiotherapy was delivered to a 1.0cm target surrounding the lumpectomy bed using high-dose-rate brachytherapy using either a single-lumen (66%) or multi-lumen (36%) balloon. Dose and fractionation was 34 Gy in 10 fractions BID for most patients (n5220) or 28 Gy in 4 fractions BID (n548) as part of two separate Phase II trials. Factors analyzed included rates of ipsilateral breast tumor recurrence (IBTR), ipsilateral mastectomy (IM), regional nodal failure (RNF), distant metastasis (DM), disease-free survival (DFS), cause-specific survival (CSS), and overall survival (OS). Results: Median age at diagnosis was 63 years and median tumor size was 10mm. 87% of women had ER positive tumors with either a negative (89%) or close margin (9.5%). Most women had an invasive tumors less than 2cm (74.6%) or pure DCIS (25%). The rate of lymph node positive disease was low at 4.8% with maximum number of positive lymph nodes allowed #3. A minority of patients received adjuvant chemotherapy (9.9%) while 55% of patients received endocrine therapy. With a median followup of 3.9 years, a total of six patients had a recurrence within the ipsilateral breast resulting in a 5-year actuarial IBTR rate of 2.8%. Two patients received repeat breast conserving therapy while four patients elected for an ipsilateral mastectomy equating to a 5-year ipsilateral mastectomy rate of 1.8%. In patients 65 years or older (n5145), there were no ipsilateral mastectomies (five-year IM rate 5 0%). Rates of RNF and DM at five
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years were 0% and 1.9%, respectively. Disease-free survival, CSS, and OS were 95.2%, 98.4%, and 93.3%. Conclusions: In our patient population, balloon-based brachytherapy appears to be an effective method of adjuvant radiotherapy following breast conserving surgery. Clinical outcomes at five years using two different dose fractionation patterns were excellent. The rate of ipsilateral mastectomy following balloon-based APBI appears to be low, especially in women over the age of 65.
PD25 Long-Term Results Including Mastectomy Rates of Accelerated Partial Breast Brachytherapy Treatment at a Single Institution Waseet Vance, MD, Paul Anderson, MD, Raleigh Anderson, Thomas Neumann, MD, Catherine Ronaghan, MD, Murali Nair, PhD, Marty White, RTT, CMD, Jennifer Davis, RTT, CMD. Radiation Oncology, Joe Arrington Cancer Research and Treatment Center, Lubbock, TX. Purpose: To investigate the cause and incidence rate of mastectomy in a cohort of patients from a single institution community cancer center with long-term experience in accelerated partial breast brachytherapy using a variety of devices and techniques. Materials and Methods: Retrospective review of 360 patients treated with lumpectomy and partial breast brachytherapy from 5/30/2000 through 4/30/ 2012. Accelerated partial breast brachytherapy devices and techniques utilized include MammoSite, Contura, SAVI, and interstitial catheter based treatment. 318 patients with at least 12 months of followup are the foundation of this report. Mastectomy rates, cause for mastectomy, type of implant, recurrence rates, type of recurrence, and survival were established. Results: Of the 318 patients treated with brachytherapy followup was from 12 to 144 months, median followup was 56 months and mean was 54.5 months. Mastectomies were performed on 10 out of 318 (3.1%) patients, 7 bilateral and 3 unilateral. Five were due to involved breast recurrences, 3 contralateral breast recurrences, one chronic mastitis and one for cosmetic reasons. All patients that had mastectomies were alive and without disease at their last visit. Local recurrence as part of initial recurrence was seen in 6 of 318 (1.9%) patients and 2 patients with distant metastasis (one deceased and 1 alive with disease). Of the 318 patients 291 remain alive without disease (91%). Two patients were lost to followup at 18 and 49 months. They are presumed dead from disease for statistical purposes, but were alive at last contact. Conclusions: These long-term results from a community cancer center confirm that in an appropriately selected patient population partial breast brachytherapy is a safe and efficacious treatment modality using a variety of partial breast brachytherapy techniques. Excellent long-term breast cancer control with low post treatment mastectomy rates are achieved. Our study is consistent with published data from large academic institutions that have substantial experience using partial breast brachytherapy techniques and adhere to appropriate treatment guidelines.
PD26 Breast Boost Using Non-Invasive Image-Guided Breast Brachytherapy Vs. En Face Electrons: A 2:1 Matched-Pair Analysis Kara Lynne Leonard, MD1, Jaroslaw T. Hepel, MD1,2, John R. Styczynski2, Jessica R. Hiatt, MS2, Thomas A. DiPetrillo, MD1,2, David E. Wazer, MD1,2. 1Radiation Oncology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA; 2Radiation Oncology, Rhode Island Hospital, Brown Alpert Medical School, Providence, RI. Purpose: The advantages of image guidance and the dosimetric characteristics of breast boost delivered with non-invasive image-guided breast brachytherapy (NIBB) have been examined and early registry data has been reported. The present analysis compares clinical outcomes and
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Abstracts / Brachytherapy 12 (2013) S11eS77
acute and late toxicity in patients treated with NIBB boost to those in patients treated with electron boost (EB). Materials and Methods: Women with early stage breast cancer treated with whole breast irradiation (WBI) and NIBB boost at our institution were identified. From among all patients treated with WBI and EB at our institution during the same time period, controls identified as the best possible match with respect to age, stage, chemotherapy use, fractionation, and when possible with respect to breast size and smoking status, were chosen for a 2:1 comparison. Acute toxicity, late toxicity, and oncologic outcomes were reviewed for each patient and matched control. Two-tailed Fisher’s exact test was used to evaluate associations between patient/tumor factors and toxicity. McNemar non-parametric test was used to evaluate for marginal homogeneity between matched pairs with respect to acute and late toxicity. Results: One hundred forty-one patients were included in the analysis: 47 patients treated with NIBB boost between May 2009 and May 2012 and 94 controls matched 2:1 treated during the same interval. Boost was delivered with en face electrons for 93 controls and with 3D-CRT minitangents for one. Mean age was 58 years in each group. The majority of patients had stage I breast cancer (n 5 84) or DCIS (n 5 36). Both NIBB boost and electron boost were well tolerated. Four patients in the NIBB group and 9 patients in the EB group required a treatment break (McNemar OR 5 .71 (.18-2.6); p 5 .77). Grade 2þ desquamation developed in 39% (n 5 18) of patients treated with NIBB boost and in 52% (n 5 49) of patients treated with electron boost (OR 5.52 (.241.06); p 5 0.07). Breast size, electron energy, and fractionation predicted for acute desquamation (p ! .0001, p ! .001, and p 5 .006); patient age and use of chemotherapy did not (p 5 0.56, p 5 0.21, respectively). Median followup was 13.6 months for the entire cohort. One patient (2%) who received NIBB boost had Grade 2þ skin/subcutaneous fibrosis 15 months after completion of treatment. Among those treated with EB, 9 patients (9.5%) developed Grade 2þ subcutaneous fibrosis and one patient had recurrent breast cellulitis. Two patients who received NIBB boost and one patient who received EB had stable nipple inversion. Among the 70 pairs with $4 months of followup, median followup was 12 months for the NIBB boost group and 15.6 months for the EB group. Matched pair comparison revealed that the incidence of subcutaneous fibrosis was borderline statistically significantly lower in those treated with NIBB boost as compared to those treated with EB (OR 5 .14 (.0031.1); p 5 0.077). There was statistically significantly less combined skin/ subcutaneous toxicity in those treated with NIBB than in those treated with EB (OR 5.13 (.003-.93); p 5 0.046). Breast size and fractionation did not predict for late skin/subcutaneous toxicity. There was one internal mammary node failure in the EB group with no other locoregional failures noted in either group. Conclusions: NIBB boost is associated with favorable clinical outcomes as compared to those seen with electron boost.
energy electronic x-ray source, Xoft Axxent, is currently used for accelerated partial breast irradiation (APBI). Recent literature indicates the importance of properly segmenting adipose and mammary tissue for breast dose calculation with low energy photons. The purpose of this study is to highlight the importance of proper tissue segmentation, applicator modeling and radiation transport in APBI by reporting the dose discrepancies stemming from the usage of TG-43 dosimetry. Materials and Methods: GEANT4.9.5 was used to simulate dose distributions in an APBI patient geometry. Patient CT images were voxelized and segmented into various tissues based on a breast modeling scheme. The balloon applicator was modeled using manufacturer’s data. The source was a phase space file derived from the validated source model. The MC simulations were calculated using the original treatment parameters; source strength, dwell positions and times. The MC dosimetric indices (PTV and skin) were compared to the TG-43 treatment plan. Results: A validation simulation using a water-based geometry agreed to within 1% of the treatment plan’s D90. The patient geometry was scored in dose to water in medium (Dw,m) and compared, as a ratio, against the TG-43 plan (Dw,w) (figure). All dose indices demonstrate a decrease in Dw,m compared to Dw,w on the order of 10-30%. The TG-43 D90 is reduced by 20% in Dw,m. The D0.1cc for the skin showed a 30% reduction when recalculated in MC. Individual tissues types segmented (Figure) show dose variations with closely neighboring tissues of different types, especially glandular and adipose. The wall of the balloon applicator reduces the dose fluence considerably due to the presence of barium sulfate (A high-Z material). Further inaccuracies can be attributed to replacement of water backscatter with air/lung tissue.
PD27
Figure. Top Right: Isodose comparison of MC-based(solid lines) versus TG-43-based dosimetry(dashed lines) Bottom: Ratio of Dw,w to Dw,m Black line denotes PTV. Dose to air is reported as zero. Top left: HU-based tissue segmentation of the breast. Conclusions: Results indicate that effects of under-dosing on the dose distribution for Dw,m compared to Dw,w. This study demonstrates the need for more comprehensive dosimetry model to the current TG-43 dose formulation.
Dosimetric Impact of Tissue Heterogeneity in Low Energy Accelerated Partial Breast Irradiation: A Monte Carlo Study Shane White, MSc1, Guillaume Landry, MSc1, Randall W. Holt, PhD2,3, Thomas Rusch, PhD3, Luc Beaulieu, PhD5,6, Frank Verhaegen, PhD1,4, Brigitte Reniers, PhD1. 1Radiation Oncology, GROW School for Oncology and Developmental Biology, Maastro Clinic, Maastricht, The Netherlands; 2 Pacific Crest Medical Physics Inc, Chico, CA; 3Xoft, Inc, and Icad Company, Sunnyvale, CA; 4Oncology, McGill University, Montreal, QC, Canada; 5Centre Hospitalier Universitaire de Quebec, Quebec, QC, Canada; 6Physics, Medical Physics, and Optics, Universite Laval, Quebec, QC, Canada. Purpose: The TG-186 report has updated guidelines for reporting dose in brachytherapy. The current TG-43 protocol ignores the effects of tissue heterogeneities on dose distributions from low energy sources (!50keV). One alternative dose calculation method is Monte Carlo (MC) dosimetry, which can accurately calculate dose distributions in realistic patient geometries such as those derived from CT imaging. A miniature low
PD28 Brachytherapy-Based Accelerated Partial Breast Irradiation Offers Equal Efficacy in a Shorter Treatment Time than Canadian Whole Breast Hypofractionation Peter Y. Chen, MD, FACR, Jessica Wobb, MD, Michelle Wallace, RN, Hong Ye, MS, Ashley Fowler, BS, J. Ben Wilkinson, MD, Donald Brabbins, MD. Radiation Oncology, Beaumont Health System, Royal Oak, MI.
PD24 Low Rate of Mastectomy following Accelerated Partial Breast Irradiation Using Balloon-Based Brachytherapy J. Ben Wilkinson, MD1, Peter Y. Chen, MD1, Michelle Wallace, RN1, Ashley Fowler, BS1, M. Saada Jawad, MD1, Mark Sittig, BA2, Hong Ye, MS1, Donald Brabbins, MD1, Inga S. Grills, MD1. 1Radiation Oncology, William Beaumont Hospital, Royal Oak, MI; 2Tulane University School of Medicine, New Orleans, LA. Purpose: To evaluate rate of ipsilateral mastectomy and clinical outcomes at five years following accelerated partial breast irradiation (APBI) using balloon-based brachytherapy (BBB) at a single institution. Materials and Methods: An IRB-approved retrospective analysis of women treated with APBI using balloon-based brachytherapy with at least one year of followup was conducted to determine the rate of ipsilateral mastectomy at five years after completion of treatment. 268 patients were identified and eligible for this analysis with followup complete through September 2012. Adjuvant radiotherapy was delivered to a 1.0cm target surrounding the lumpectomy bed using high-dose-rate brachytherapy using either a single-lumen (66%) or multi-lumen (36%) balloon. Dose and fractionation was 34 Gy in 10 fractions BID for most patients (n5220) or 28 Gy in 4 fractions BID (n548) as part of two separate Phase II trials. Factors analyzed included rates of ipsilateral breast tumor recurrence (IBTR), ipsilateral mastectomy (IM), regional nodal failure (RNF), distant metastasis (DM), disease-free survival (DFS), cause-specific survival (CSS), and overall survival (OS). Results: Median age at diagnosis was 63 years and median tumor size was 10mm. 87% of women had ER positive tumors with either a negative (89%) or close margin (9.5%). Most women had an invasive tumors less than 2cm (74.6%) or pure DCIS (25%). The rate of lymph node positive disease was low at 4.8% with maximum number of positive lymph nodes allowed #3. A minority of patients received adjuvant chemotherapy (9.9%) while 55% of patients received endocrine therapy. With a median followup of 3.9 years, a total of six patients had a recurrence within the ipsilateral breast resulting in a 5-year actuarial IBTR rate of 2.8%. Two patients received repeat breast conserving therapy while four patients elected for an ipsilateral mastectomy equating to a 5-year ipsilateral mastectomy rate of 1.8%. In patients 65 years or older (n5145), there were no ipsilateral mastectomies (five-year IM rate 5 0%). Rates of RNF and DM at five
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years were 0% and 1.9%, respectively. Disease-free survival, CSS, and OS were 95.2%, 98.4%, and 93.3%. Conclusions: In our patient population, balloon-based brachytherapy appears to be an effective method of adjuvant radiotherapy following breast conserving surgery. Clinical outcomes at five years using two different dose fractionation patterns were excellent. The rate of ipsilateral mastectomy following balloon-based APBI appears to be low, especially in women over the age of 65.
PD25 Long-Term Results Including Mastectomy Rates of Accelerated Partial Breast Brachytherapy Treatment at a Single Institution Waseet Vance, MD, Paul Anderson, MD, Raleigh Anderson, Thomas Neumann, MD, Catherine Ronaghan, MD, Murali Nair, PhD, Marty White, RTT, CMD, Jennifer Davis, RTT, CMD. Radiation Oncology, Joe Arrington Cancer Research and Treatment Center, Lubbock, TX. Purpose: To investigate the cause and incidence rate of mastectomy in a cohort of patients from a single institution community cancer center with long-term experience in accelerated partial breast brachytherapy using a variety of devices and techniques. Materials and Methods: Retrospective review of 360 patients treated with lumpectomy and partial breast brachytherapy from 5/30/2000 through 4/30/ 2012. Accelerated partial breast brachytherapy devices and techniques utilized include MammoSite, Contura, SAVI, and interstitial catheter based treatment. 318 patients with at least 12 months of followup are the foundation of this report. Mastectomy rates, cause for mastectomy, type of implant, recurrence rates, type of recurrence, and survival were established. Results: Of the 318 patients treated with brachytherapy followup was from 12 to 144 months, median followup was 56 months and mean was 54.5 months. Mastectomies were performed on 10 out of 318 (3.1%) patients, 7 bilateral and 3 unilateral. Five were due to involved breast recurrences, 3 contralateral breast recurrences, one chronic mastitis and one for cosmetic reasons. All patients that had mastectomies were alive and without disease at their last visit. Local recurrence as part of initial recurrence was seen in 6 of 318 (1.9%) patients and 2 patients with distant metastasis (one deceased and 1 alive with disease). Of the 318 patients 291 remain alive without disease (91%). Two patients were lost to followup at 18 and 49 months. They are presumed dead from disease for statistical purposes, but were alive at last contact. Conclusions: These long-term results from a community cancer center confirm that in an appropriately selected patient population partial breast brachytherapy is a safe and efficacious treatment modality using a variety of partial breast brachytherapy techniques. Excellent long-term breast cancer control with low post treatment mastectomy rates are achieved. Our study is consistent with published data from large academic institutions that have substantial experience using partial breast brachytherapy techniques and adhere to appropriate treatment guidelines.
PD26 Breast Boost Using Non-Invasive Image-Guided Breast Brachytherapy Vs. En Face Electrons: A 2:1 Matched-Pair Analysis Kara Lynne Leonard, MD1, Jaroslaw T. Hepel, MD1,2, John R. Styczynski2, Jessica R. Hiatt, MS2, Thomas A. DiPetrillo, MD1,2, David E. Wazer, MD1,2. 1Radiation Oncology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA; 2Radiation Oncology, Rhode Island Hospital, Brown Alpert Medical School, Providence, RI. Purpose: The advantages of image guidance and the dosimetric characteristics of breast boost delivered with non-invasive image-guided breast brachytherapy (NIBB) have been examined and early registry data has been reported. The present analysis compares clinical outcomes and
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Abstracts / Brachytherapy 12 (2013) S11eS77
acute and late toxicity in patients treated with NIBB boost to those in patients treated with electron boost (EB). Materials and Methods: Women with early stage breast cancer treated with whole breast irradiation (WBI) and NIBB boost at our institution were identified. From among all patients treated with WBI and EB at our institution during the same time period, controls identified as the best possible match with respect to age, stage, chemotherapy use, fractionation, and when possible with respect to breast size and smoking status, were chosen for a 2:1 comparison. Acute toxicity, late toxicity, and oncologic outcomes were reviewed for each patient and matched control. Two-tailed Fisher’s exact test was used to evaluate associations between patient/tumor factors and toxicity. McNemar non-parametric test was used to evaluate for marginal homogeneity between matched pairs with respect to acute and late toxicity. Results: One hundred forty-one patients were included in the analysis: 47 patients treated with NIBB boost between May 2009 and May 2012 and 94 controls matched 2:1 treated during the same interval. Boost was delivered with en face electrons for 93 controls and with 3D-CRT minitangents for one. Mean age was 58 years in each group. The majority of patients had stage I breast cancer (n 5 84) or DCIS (n 5 36). Both NIBB boost and electron boost were well tolerated. Four patients in the NIBB group and 9 patients in the EB group required a treatment break (McNemar OR 5 .71 (.18-2.6); p 5 .77). Grade 2þ desquamation developed in 39% (n 5 18) of patients treated with NIBB boost and in 52% (n 5 49) of patients treated with electron boost (OR 5.52 (.241.06); p 5 0.07). Breast size, electron energy, and fractionation predicted for acute desquamation (p ! .0001, p ! .001, and p 5 .006); patient age and use of chemotherapy did not (p 5 0.56, p 5 0.21, respectively). Median followup was 13.6 months for the entire cohort. One patient (2%) who received NIBB boost had Grade 2þ skin/subcutaneous fibrosis 15 months after completion of treatment. Among those treated with EB, 9 patients (9.5%) developed Grade 2þ subcutaneous fibrosis and one patient had recurrent breast cellulitis. Two patients who received NIBB boost and one patient who received EB had stable nipple inversion. Among the 70 pairs with $4 months of followup, median followup was 12 months for the NIBB boost group and 15.6 months for the EB group. Matched pair comparison revealed that the incidence of subcutaneous fibrosis was borderline statistically significantly lower in those treated with NIBB boost as compared to those treated with EB (OR 5 .14 (.0031.1); p 5 0.077). There was statistically significantly less combined skin/ subcutaneous toxicity in those treated with NIBB than in those treated with EB (OR 5.13 (.003-.93); p 5 0.046). Breast size and fractionation did not predict for late skin/subcutaneous toxicity. There was one internal mammary node failure in the EB group with no other locoregional failures noted in either group. Conclusions: NIBB boost is associated with favorable clinical outcomes as compared to those seen with electron boost.
energy electronic x-ray source, Xoft Axxent, is currently used for accelerated partial breast irradiation (APBI). Recent literature indicates the importance of properly segmenting adipose and mammary tissue for breast dose calculation with low energy photons. The purpose of this study is to highlight the importance of proper tissue segmentation, applicator modeling and radiation transport in APBI by reporting the dose discrepancies stemming from the usage of TG-43 dosimetry. Materials and Methods: GEANT4.9.5 was used to simulate dose distributions in an APBI patient geometry. Patient CT images were voxelized and segmented into various tissues based on a breast modeling scheme. The balloon applicator was modeled using manufacturer’s data. The source was a phase space file derived from the validated source model. The MC simulations were calculated using the original treatment parameters; source strength, dwell positions and times. The MC dosimetric indices (PTV and skin) were compared to the TG-43 treatment plan. Results: A validation simulation using a water-based geometry agreed to within 1% of the treatment plan’s D90. The patient geometry was scored in dose to water in medium (Dw,m) and compared, as a ratio, against the TG-43 plan (Dw,w) (figure). All dose indices demonstrate a decrease in Dw,m compared to Dw,w on the order of 10-30%. The TG-43 D90 is reduced by 20% in Dw,m. The D0.1cc for the skin showed a 30% reduction when recalculated in MC. Individual tissues types segmented (Figure) show dose variations with closely neighboring tissues of different types, especially glandular and adipose. The wall of the balloon applicator reduces the dose fluence considerably due to the presence of barium sulfate (A high-Z material). Further inaccuracies can be attributed to replacement of water backscatter with air/lung tissue.
PD27
Figure. Top Right: Isodose comparison of MC-based(solid lines) versus TG-43-based dosimetry(dashed lines) Bottom: Ratio of Dw,w to Dw,m Black line denotes PTV. Dose to air is reported as zero. Top left: HU-based tissue segmentation of the breast. Conclusions: Results indicate that effects of under-dosing on the dose distribution for Dw,m compared to Dw,w. This study demonstrates the need for more comprehensive dosimetry model to the current TG-43 dose formulation.
Dosimetric Impact of Tissue Heterogeneity in Low Energy Accelerated Partial Breast Irradiation: A Monte Carlo Study Shane White, MSc1, Guillaume Landry, MSc1, Randall W. Holt, PhD2,3, Thomas Rusch, PhD3, Luc Beaulieu, PhD5,6, Frank Verhaegen, PhD1,4, Brigitte Reniers, PhD1. 1Radiation Oncology, GROW School for Oncology and Developmental Biology, Maastro Clinic, Maastricht, The Netherlands; 2 Pacific Crest Medical Physics Inc, Chico, CA; 3Xoft, Inc, and Icad Company, Sunnyvale, CA; 4Oncology, McGill University, Montreal, QC, Canada; 5Centre Hospitalier Universitaire de Quebec, Quebec, QC, Canada; 6Physics, Medical Physics, and Optics, Universite Laval, Quebec, QC, Canada. Purpose: The TG-186 report has updated guidelines for reporting dose in brachytherapy. The current TG-43 protocol ignores the effects of tissue heterogeneities on dose distributions from low energy sources (!50keV). One alternative dose calculation method is Monte Carlo (MC) dosimetry, which can accurately calculate dose distributions in realistic patient geometries such as those derived from CT imaging. A miniature low
PD28 Brachytherapy-Based Accelerated Partial Breast Irradiation Offers Equal Efficacy in a Shorter Treatment Time than Canadian Whole Breast Hypofractionation Peter Y. Chen, MD, FACR, Jessica Wobb, MD, Michelle Wallace, RN, Hong Ye, MS, Ashley Fowler, BS, J. Ben Wilkinson, MD, Donald Brabbins, MD. Radiation Oncology, Beaumont Health System, Royal Oak, MI.