Breast Brachytherapy Research Articles

Development and Clinical Validation of a 3D Ultrasound System for Permanent Breast Seed Implant Brachytherapy

Permanent Breast Seed Implant (PBSI) is a novel form of breast brachytherapy completed in a single 1-2h procedure. PBSI planning uses CT simulation and treatment involves implanting Pd-103 seeds in and around the breast seroma via needles inserted through a template and guided by free-hand 2D ultrasound. The seroma shape and size vary from CT images to ultrasound and currently neither 3D images nor real-time guidance are available for PBSI. A 3D ultrasound (3DUS) system has been developed to fulfill these needs. This study extends this work to validate the 3DUS clinical implementation in PBSI planning and delivery procedure.

A Plan Quality Assurance (QA) Method for HDR Breast Brachytherapy with Multi-Lumen Balloon Applicator and HDR Interstitial Prostate Brachytherapy

A challenge facing the physics community has been quick plan quality checks for high-dose-rate (HDR) brachytherapy treatment planning. This study aims to develop a QA method of manually verifying the planned treatment time from treatment planning system (TPS) for HDR breast brachytherapy using multi-lumen balloon applicators and HDR interstitial prostate brachytherapy.

Programmatic Improvements to the Workflow Associated with the Accuboost Breast Brachytherapy Procedure

Programmatic Improvements to the Workflow Associated with the Accuboost Breast Brachytherapy Procedure

Abstract ES4-3: Techniques and technical considerations

Abstract Purpose: Partial breast irradiation (PBI) treats the lumpectomy cavity and a margin of adjacent breast tissue allowing for a reduction in treatment volume, duration and potentially toxicity. Body: Multiple PBI techniques are available. Interstitial brachytherapy (IB) represents the oldest PBI technique; mature data from randomized trials are available with 5-10 year follow-up and demonstrate comparable local control and toxicity profiles. Technically, multiple target volume definitions are currently utilized. Applicator based brachytherapy has evolved from single-lumen applicators, increasing the degrees of freedom for treatment planning. Prospective, non-randomized 5 year data are available with applicator based brachytherapy, demonstrating low rates of recurrence, comparable rates of toxicity, and high rates of excellent/good cosmetic outcomes. The treatment volume for applicator based brachytherapy is 1 cm surrounding the device, with adjustments for the skin and chest wall. External beam radiation therapy includes 3D-CRT, IMRT and proton based techniques. Data from 3D-CRT studies have suggested higher toxicities and inferior cosmetic outcomes. However, randomized studies evaluating IMRT PBI have not, demonstrating comparable or improved toxicity and cosmetic outcomes. Intraoperative radiation therapy (IORT) is unique as two randomized trials have evaluated IORT and found higher rates of local recurrence as compared to WBI. Low-energy IORT delivers 25-30% of prescription at 1 cm, different from other PBI techniques while electron IORT allows for modulation of energy/depth. Currently, ASTRO PBI guidelines do not recommend low-energy IORT off protocol and electron IORT only for suitable risk patients, while ABS guidelines do not recommend IORT off trial. Finally, newer PBI techniques include non-invasive image-guided breast brachytherapy and permanent seed implants. As with all PBI techniques, use of guidelines for the application of PBI is encouraged for patient selection and the application of well-established dosimetric criteria for target coverage and normal tissue tolerances. Partial Breast TechniquesTechniqueRandomized TrialsDose/Target VolumesDurationInterstitial BrachytherapyNational Institute of Oncology (Hungary);GEC-ESTRO;NSABP B-39/RTOG 041336.4 Gy/7 fx BID;32 Gy/8 fx BID, 30.3 Gy/7 fx BID, 50 Gy PDR; 34 Gy/10 fx BID15-20 mm expansion (limit skin, chest wall);20 mm minimum (sum of pathologic margin + radiation margin) CTV; Cavity + 15 mm (5 mm from skin, posterior breast)4-5 treatment days;4-5 treatment days; 5 treatment daysApplicator Based BrachytherapyNSABP B-39/RTOG 041334 Gy/10 fx BID10 mm from surface/device (5 mm from skin and posterior breast)5 treatment days3D-CRTNSABP B-39/RTOG 0413; RAPID38.5 Gy/10 fx BID; 38.5 Gy/10 fx BID15 mm CTV (5 mm from skin and posterior breast), 10 mm PTV, PTV-EVAL (5 mm from skin, posterior breast); 10 mm CTV inside breast, 10 mm PTV5 treatment days; 5 treatment daysIMRTUniversity of Florence; IMPORT LOW30 Gy/5 fx QOD; 40 Gy/15 fx10 mm CTV (3 mm from skin), 10 mm PTV ( 4 mm into lung, 3 mm from skin); 15 mm CTV (5 mm from skin, pec fascia)/10 mm PTV (5 mm from skin)5 treatment days over 2 weeks; 3 weeks (15 treatments) Conclusions: Partial breast irradiation represents a standard of care strategy for appropriately selected patients. Citation Format: Vicini F. Techniques and technical considerations [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr ES4-3.

Three-Fraction Accelerated Partial Breast Irradiation (APBI) Delivered With Brachytherapy Applicators Is Feasible and Safe: First Results From the TRIUMPH-T Trial

Shorter courses of accelerated partial-breast irradiation delivered as single-fraction intraoperative therapy are now offered as an alternative to 4 to 6weeks of whole-breast irradiation after lumpectomy. However, this approach has potential shortcomings in patient selection and target volume definition and in dosimetric, radiobiological, and logistical issues. We designed a prospective, phase 2, multi-institution clinical trial to study 2- or 3-day accelerated partial breast irradiation delivered with brachytherapy applicators. This trial treats select breast cancers after breast-conserving surgery with brachytherapy applicators that deliver 22.5Gy in 3 fractions of 7.5Gy. The planning treatment volume was 1 to 1.5cm beyond the surgical cavity. Eligible women were aged ≥45years with unicentric invasive or in situ tumors ≤3.0cm with positive estrogen or progesterone receptors and no metastasis to axillary nodes that have been excised with negative margins. Strict dosimetric parameters were required to be met before acceptance into the trial. A group of 200 patients was prospectively enrolled and followed for a minimum of 6months. Two- or 3-day brachytherapy was associated with low acute or subacute toxicity, 97.25% excellent or good cosmetic outcomes, and excellent local control in select breast cancers. Ultrashort breast brachytherapy is dosimetrically feasible and can be delivered with excellent short-term tolerance and low toxicity.

The effect of breast phantom, and geometry on dose distribution in breast brachytherapy using the strut-adjusted volume implant and contura applicators

Context: Accelerated partial breast irradiation using brachytherapy is a postlumpectomy treatment to reduce cancer recurrence and a choice for people in the early-stage breast cancer. Although accurate dosimetry is necessary to obtain successful clinical outcomes, the usual commercial treatment planning systems use a simple water phantom to simulate the patient. Hence, the precise attenuated radiation and also the scattering effects occurred in real situations may be dosimetrically ignored. Aims: The purpose of this study is to use Monte Carlo simulation to obtain the effect of phantom material and geometry corrections on dose distribution of the strut-adjusted volume implant (SAVI) and Contura high-dose-rate brachytherapy applicators of breast cancer. Settings and Design: Contura with four lumens surrounding the central one and also SAVI with eight peripheral source channels are separately simulated into the breast phantoms. 192Ir high dose rate sources are located on dwell positions in each applicator. Subjects and Methods: The applicators were simulated inside three different phantom geometry and materials. The dose distribution and dose-volume histograms for each phantom were obtained for typical treatment. Gamma index evaluation is performed to examine the dose distribution according to the water phantom for each trial. Results: According to the results for SAVI and Contura applicators, breast material correction shows about 1% deviations from the calculations for water in most points of the breast. Maximum differences are not >3% that are found near the skin. Conclusion: Deviations from the water phantom in both SAVI and Contura treatments show good conformity especially in Contura and it seems that no serious dosimetric correction is necessary for simple water phantom. Although the results for SAVI were not observed with great deviations from water, areas with high-gradient dose need to be precisely considered.

A prospective comparison of subjective and objective assessments of cosmetic outcomes following breast brachytherapy.

PurposeWe evaluated agreement between subjective and objective methods of cosmesis scoring in an accelerated partial breast irradiation (APBI) cohort.Material and methodsConsecutive women treated with APBI using interstitial brachytherapy reported for clinical follow-up every 6 months. Single cross-sectional assessment of the breast cosmesis was done by a radiation oncologist (subjective method) using Harvard scale and by photographic assessment using BCCT.core (Breast Cancer Conservative Treatment. Cosmetic results, version 3.1) software (objective method) at 18-36 months post-APBI. The agreement between subjective and objective methods for the overall score as well as individual subjective/objective subdomains was computed using kappa statistics. ANOVA was used to test the correlation between objective indices and subjective subdomains.ResultsThe agreement between the subjective (physician) and objective assessment was good with a kappa of 0.673. Overall, 77 (98.7%) patients were satisfied with the overall outcomes of breast conservation therapy. The kappa agreement between physician and patient scoring was 0.457 (95% CI: 0.240-0.674). Among the subjective subdomains, location of the nipple areola complex (NAC) had good agreement with both the overall subjective and objective score, with the kappa of 0.778 and 0.547, respectively. In the objective indices, BCE (breast compliance evaluation), LBC (lower breast contour), and UNR (unilateral nipple retraction) correlated significantly with the subjective subdomains: location of the NAC, breast size, and shape (p < 0.05 for all indices).ConclusionsGood agreement exists for overall cosmetic outcomes measured by subjective and objective methods. Location of the NAC, breast size and shape are the most important parameters determining cosmetic outcomes irrespective of the method of assessment.

Three-Fraction Intracavitary Accelerated Partial Breast Brachytherapy: Early Provider and Patient-Reported Outcomes of a Novel Regimen

To report early adverse events and patient-reported outcomes (PROs) of 3-fraction intracavitary catheter-based partial breast brachytherapy (ICBB). Eligible women ≥50years of age with ≤2.5-cm, lymph node-negative invasive or in situ breast cancer underwent breast-conserving surgery and placement of a brachytherapy applicator. ICBB was initiated on the second weekday after surgery and prescribed to 21Gy in 3 once-daily fractions. Common Terminology Criteria for Adverse Events, version 4.0; 10-point linear analog scale assessment; the PRO version of the Common Terminology Criteria for Adverse Events; and the Harvard Breast Cosmesis Scale were used for provider and patient-reported assessments. Seventy-three women were treated for invasive (79%) or in situ (21%) breast cancer. The median time to completion of surgery and radiation therapy was 6days. After 14-months median follow-up, 2 patients (3%) had developed breast infections that resolved with oral antibiotics. There was no other treatment-associated adverse event grade ≥2. The grade 1 seroma rate at 3months was 20%, which dropped to 8% at 12months; no events required intervention. At 12months, 91% of patients reported an overall quality of life score as ≥8 of 10, and patient-reported cosmesis was good or excellent in 95%. All patients are alive without relapse at the last follow-up. Three-fraction ICBB is associated with low rates of early provider and patient- reported adverse events and compares favorably with early outcomes of more protracted ICBB regimens, including twice-daily (3.4Gy×10) fractionation studied in the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-39. Further investigation is warranted.

Subcutaneous spacer injection to reduce skin toxicity in breast brachytherapy: A pilot study on mastectomy specimens

PurposeAccelerated partial breast irradiation is a treatment option for selected patients with early-stage breast cancer. Some accelerated partial breast irradiation techniques lead to skin toxicity with the skin dose as a main risk factor. Biodegradable spacers are effective and safe in prostate brachytherapy to protect the rectum. We hypothesize that a subcutaneous spacer injection reduces the skin dose in breast brachytherapy. Methods and MaterialsUltrasound-guided spacer injections, either hyaluronic acid (HA) or iodined polyethylene glycol (PEG), were performed on fresh mastectomy specimens. Success was defined as a spacer thickness of ≥5 mm in the high-dose skin area. Usability was scored using the system usability scale. Pre and postinjection CT scans were used to generate low-dose-rate seed brachytherapy treatment plans after defining a clinical target volume. Maximum dose to small skin volumes (D0.2cc) and existence of hotspots (isodose ≥90% on 1 cm2 of skin) were calculated as skin toxicity indicators. ResultsWe collected 22 mastectomy specimens; half had HA and half had PEG injection. Intervention success was 100% for HA and 90.9% for PEG (p = NS). Hydrodissection was feasible in 81.8% with HA and 63.6% with PEG. Median system usability scale score was 97.5 for HA and 82.5 for PEG (p < 0.001). Mean D0.2cc was 80.8 Gy without spacer and 53.7 Gy with spacer (p < 0.001). Skin hotspots were present in 40.9% without spacer but none with spacer (p < 0.001). ConclusionsA spacer injection in mastectomy specimens is feasible. An extra 5 mm space is always achieved, thereby potentially reducing the skin dose dramatically in low-dose-rate seed breast brachytherapy.

Consideration of accurate dose distribution for Contura balloon catheter in breast brachytherapy with MCNP5 simulation

Introduction: Contura is a balloon applicator that used to deliver intra cavity radiation for Partial Breast Irradiation (PBI) treatments. Contura with 4 peripheral lumens surrounding the central, for loading HDR sources from an after loader system can provide an asymmetric dose distribution and gives a more flexible shape of dose than earlier balloon applicators such as Mammo site. Accurate dosimetry is necessary to avoid deviations in delivered dose from that prescribed for a successful treatment. In this study we tried to explore possible uncertainties in simple water phantom measurements compared to the realistic breast cancer treatment condition with Contura. Materials and Methods: MCNP5 simulations were performed to have investigations on dose distribution. Several trials have been introduced to study the effects of corrections for phantom geometry and content. First, dose distributions were considered for an ICRU-44 breast phantom and the obtained results were compared with water. In next trial geometry was corrected to take the effects of an air cavity as lung inside the chest into account. Investigations were followed in third trial with correction at the breast skin surface to evaluate tissue-air interferences at skin. 192-Ir HDR sources were simulated on 7 dwell positions on each lumen. Lumens were defined inside a water sphere as saline filled balloon. Results have presented as dose distribution plots in breast and dose volume histogram analysis for PTV. Results: The ICRU-44 breast phantom demonstrated differences less than 1% in breast from water. Air cavity as the lung tissue has not shown significant effects on dose distribution in the breast, but correction at skin surface has caused up to 5% overestimations proximity near this area. However almost in other places in the corrected breast, the matched results to the water phantom have been observed. Conclusion: The results of this investigation indicate no significant deviations from a water phantom without any corrections. Therefore, treatment planning systems can still be used without significant uncertainties in treatment of breast cancer using HDR brachytherapy with Contura device. Differences can be corrected to provide a precise dosimetry but because of underestimated values obtained in water phantom dosimetry it can be a conservative approximation.

Monte Carlo investigation on precise dosimetry of HDR breast brachytherapy with Accuboost

Introduction: Accuboost is a HDR brachytherapy system in early stages breast cancer treatment. This device provides a completely noninvasive procedure with parallel-opposed radiation from two immobilizing peripheral applicators that caused it a preferred option of modalities to choose. In most commercial treatment planning systems, tissues are considered as a simple water phantom. Inaccuracies arised from geometry and compositions can lead to deviations in interested dose distribution. This study intends to simulate HDR breast brachytherapy with Accuboost device in order to consider requirement corrections to have an accurate treatment dosimetry. Materials and Methods: MCNP5 simulation is employed to model phantoms in dosimetric measurements. We tried to take geometrical corrections into account in three phantoms. Dose distributions as dose volume histogram parameters and isodose plots obtained from these phantoms are compared to those of water. Corrections are included using real breast tissue with ICRU-44 breast composition, chest defined with an air cavity as lung and a curved surface to introduce a more realistic contour for breast skin. Accuboost is simulated with radiations from eighteen HDR 192-Ir sources on each applicator with appropriate tungsten shields. Results: Differences in most regions with less than 1% to water and maximum value about 5 % have been observed in phantom with ICRU-44 breast material compared to the water. Lung presence have increased deviations a few percent but it has not significantly differed. In phantom with all corrections maximum differences are almost the same as both earlier and deviations with about 5-7% are found near the chest and around the breast skin not in contact to applicators. Conclusion: Based on the results, although discrepancies between corrected phantom and water phantom are in areas near the skin the main differences are in clinical accepted uncertainties and other points of tissue have shown accommodatian. Therefore essential correction may be not needed.

A randomized controlled trial testing a hyaluronic acid spacer injection for skin toxicity reduction of brachytherapy accelerated partial breast irradiation (APBI): a study protocol

BackgroundAccelerated partial breast irradiation (APBI) is a treatment option for selected early stage breast cancer patients. Some APBI techniques lead to skin toxicity with the skin dose as main risk factor. We hypothesize that a spacer injected between the skin and target volume reduces the skin dose and subsequent toxicity in permanent breast seed implant (PBSI) patients.MethodsIn this parallel-group, single-center, randomized controlled trial, the effect of a subcutaneous spacer injection on skin toxicity among patients treated with PBSI is tested. Eligibility for participation is derived from international guidelines for suitable patients for partial breast radiotherapy, e.g. women aged ≥ 50 years with a histologically proven non-lobular breast carcinoma and/or ductal carcinoma in situ (DCIS), tumor size ≤ 3 cm, node-negative, and PBSI technically feasible. Among exclusion criteria are neoadjuvant chemotherapy, lymphovascular invasion, and allergy for hyaluronic acid. For the patients allocated to receive spacer, after the PBSI procedure, 4–10 cc of biodegradable hyaluronic acid (Barrigel™, Palette Life Sciences, Santa Barbara, CA, USA or Restylane SubQ®, Galderma Benelux, Breda, the Netherlands) is injected directly under the skin using ultrasound guidance to create an extra 0.5–1 cm space between the treatment volume and the skin. The primary outcome is the rate of telangiectasia at two years, blindly assessed using Bentzen’s 4-point scale. Secondary outcomes include: local recurrence; disease-free and overall survival rates; adverse events (pain, redness, skin/subcutaneous induration, radiation dermatitis, pigmentation, surgical site infection); skin dose; cosmetic and functional results; and health-related quality of life.A Fisher’s exact test will be used to test differences between groups on the primary outcome.Previous studies found 22.4% telangiectasia at two years. We expect the use of a spacer could reduce the occurrence of telangiectasia to 7.7%. A sample size of 230 patients will allow for a 10% lost to follow-up rate.DiscussionIn this study, the effect of a subcutaneous spacer injection on the skin dose, late skin toxicity, and cosmetic outcome is tested in patients treated with PBSI in the setting of breast-conserving therapy. Our results will be relevant for most forms of breast brachytherapy as well as robotic radiosurgery, as skin spacers could protect the skin with these other techniques.Trial registrationNetherlands Trial Register, NTR6549. Registered on 27 June 2017.

Relationship among different skin dose definitions in high-dose-rate (HDR) balloon breast brachytherapy

To establish the relationship among various skin dosimetric indices and different volumetric definitions of skin in high-dose-rate (HDR) balloon breast brachytherapy. Fifty breast cancer patients were treated with HDR balloon brachytherapy. The MammoSite® applicator was used for 40 patients and the Contura® applicator for 10 patients. Skin structure was retrospectively defined by expanding the skin surface internal to the body with a thickness of 1, 2, 3, 4, or 5 mm in one method. In another method, the skin was defined by expanding its external to the body to demonstrate the maximum point dose on the skin surface. For each skin structure defined by six different methods, three dosimetric data points extracted from dose-volume histograms were compared. Dmax was defined as the maximum point dose, and D1cc and D0.1cc were defined as the minimum dose to 1 cm3 and 0.1 cm3 of the most irradiated skin volume, respectively. The relationship among 18 dosimetric parameters was presented in graphs, and linear curve fitting was performed to provide mathematical formulas. For each skin definition, the Dmax, D1cc, and D0.1cc values show a linear relationship such that Dmax is the largest, D0.1cc is the next, and D1cc is the smallest value. For each dosimetric parameter, there was a linear relationship among the dosimetric indices for 6 different skin definitions. For clinical use, all linear relationships were displayed in graphs and two parameters for linear fitting were provided. Average R2 value for curve fitting was 0.978. The presented relationships can be developed in each individual institution and convert one dosimetric index to another for different skin definitions.

Prospective Study of 3-Fraction Intra-Cavitary Accelerated Partial Breast Brachytherapy: Early Provider and Patient-Reported Outcomes of a Novel Regimen

The optimal dose and fractionation for accelerated partial breast irradiation (APBI) is not known. We evaluated 3-fraction brachytherapy APBI in the context of a prospective clinical trial. Our purpose is to report early adverse effects and patient-reported outcomes (PROs) of this novel regimen. Eligible women were ≥ 50 years of age with ≤2 cm estrogen receptor positive, sentinel lymph node (SLN) negative invasive or in-situ breast cancer treated with breast conserving surgery. After frozen section pathology assessment of negative surgical margins and SLN(s), a multi-channel intra-cavitary brachytherapy catheter was placed intraoperatively. APBI was initiated on the second weekday after surgery after permanent section pathology confirmation. The prescription was 21 Gy in 3, once daily, fractions targeting the lumpectomy cavity with a 1 cm expansion. Common toxicity criteria for adverse effects (CTCAE v 4.0), 10-point linear analog scales, PROs version of the CTCAE (PRO-CTCAE), and Harvard Breast Cosmesis Scale (HBCS) were utilized for provider and patient-reported assessments. Seventy-three women, median age 66 years, were treated for invasive breast cancer (79%) or ductal carcinoma in situ (21%) between 2015 and 2017. Tumor grade was 1-2 in 88%. The median time to completion of all locoregional therapy (surgery and radiotherapy) was 6 days. After 14 months median follow-up, two patients (3%) had developed breast infections that resolved with oral antibiotics. There was no other treatment-associated adverse effects ≥ grade 2. The grade 1 seroma rate at 3 months was 20% (11/56 evaluable patients) which dropped to 8% (4/49) at 12 months; none required intervention. PROs are summarized in table 1. At 12 months, 91% reported overall QOL between 8 and 10 and patient-reported cosmesis was good or excellent in 95%. All patients were alive without relapse at the last follow-up. The 3-fraction, once daily, breast brachytherapy was associated with favorable early physician and PROs. These early results compare favorably with other reports including the more universally employed twice daily (3.4 Gy x 10) fractionation being studied in NSABP B-39. A randomized trial comparing these two approaches is warranted.Abstract TU_5_3369; Table 1Patient-Reported Outcomes associated with 3-fraction brachytherapy APBIPROsLASA 10Baseline (n=56)Post-RT (n=51)3 month (n=44)6 month (n=46)12 month (n=35)Quality of Lifeα8-1095%96%89%96%91%4-74%2%7%2%9%1-31%2%4%2%0%Breast CosmesisExcellent55%41%50%65%69%Good45%49%39%26%26%Fair0%10%9%9%6%Poor0%0%2%0%0%Painβ0-361%69%86%91%86%4-632%22%7%4%9%7-107%10%7%4%6%Fatigueβ0-361%55%75%63%71%4-625%37%16%24%12%7-1014%8%9%13%17%Skin BurnsNone100%90%88%96%100%Mild0%8%12%2%0%Moderate0%0%0%0%0%Severe0%0%0%0%0%Very Severe0%2%0%2%0%LASAα: Reported on a scale of 1-10 (1 indicating “worst” and 10 indicating “best”) LASAβ: Reported on a scale of 1-10 (1 indicating “none” and 10 indicating “as bad as it can be”). Open table in a new tab

Multi-Institutional Registry Study of Accelerated Partial Breast Irradiation (APBI) Using Non-Invasive Image-Guided Breast Brachytherapy (NIBB)

Multi-Institutional Registry Study of Accelerated Partial Breast Irradiation (APBI) Using Non-Invasive Image-Guided Breast Brachytherapy (NIBB)

A 12-Year Single-Institution Experience with Accelerated Partial Breast Irradiation

Accelerated partial breast irradiation (APBI) using the implanted brachytherapy device MammoSite® was approved for routine use by the Food and Drug Administration in 2002. The American Society of Breast Surgeons MammoSite® Breast Brachytherapy Registry served as a guideline for our institution to begin offering this treatment in 2005. This report reviews our available data to provide an analysis of patient outcomes over 12 years of use at a single institution. A retrospective review was conducted of records of 150 patients who underwent APBI or attempted APBI after breast-sparing surgeries between 2006 and 2017. These charts were analyzed for documentation of patient age, cancer stage, incidence of recurrence, and posttreatment complications. Of the patients evaluated, 99 per cent (149/150) completed treatment. The median time since treatment completion is now 8.9 years. One hundred eleven patients (74% ) are now greater than five years posttreatment. Ipsilateral breast recurrence was found in 2.7 per cent of patients (4/149), and 1.3 per cent of patients (2/149) developed new primary breast tumors. Acute complications, mostly skin erythema (21%), were uncommon and self-limited. Subacute effects were generally fibrosis (13%) and mild local pain (9.4%). APBI for breast cancer after breast-conserving surgery continues to be used at our institution for select patients with good outcomes. Local control and toxicity are similar to that reported in the literature. Five-year local recurrence rates compare favorably with national trials. Occasional complications included fibrosis, persistent pain, and skin irritation.

P185] Comparison of two inverse planing algorithms HIPO and IPSA in terms of their suitability for breast brachytherapy planning

Purpose The aim of the study was to compare two algorithms of inverse brachytherapy planning Hybrid Inverse Planning Optimization (HIPO) and Inverse Planning Simulated Annealing (IPSA) in terms of their suitability for breast brachytherapy planning. The values of dose distribution parameters was evaluated for target volumes and critical organs. Methods The analysis included 40 treatment plans prepared for 20 breast cancer patients treated with brachytherapy boost using rigid interstitial applicators. For each patient CTV and organs at risk were contoured. Next two treatment plans were performed using HIPO and IPSA algorithms, with individual constrains selected to be fully comparable. The source step was set at 3 mm and dwell time gradient restriction (DTGR) at 0.5 level. Obtained treatment plans were not supposed to fulfill clinical criteria, but only to show differences between the analyzed algorithms. The collected data were analyzed statistically using the Wilcoxon test for non-parametric variables. Results For CTV the following average values were obtained: V100 71.26% and 82.35%, V150 13.85% and 19.11% and V200 6.31% and 8.39% for the IPSA and HIPO algorithms respectively. Similarly, COIN and DNR values were higher using the HIPO algorithm and were 0.65 and 0.93 and 0.2 and 0.22. In case of organs at risk, the following values were obtained: for chestwall D1cc 49.60% and 53.80% and D0.1 cc 55.62% and 60.56%, for skin D1cc 41.91% and 54.72% and D0,2 cc 55.66% and 62.1% respectively for IPSA and HIPO algorithms. The mean dose in the lung was also higher for the HIPO algorithm and reached 15.19% and 21.48% respectively. All differences were statistically significant at p Conclusions Presented results indicate the predominance of the IPSA algorithm, especially in the area of lowering doses for critical organs. However the coverage parameter COIN clearly indicates the advantage of the HIPO algorithm. This is directly due to much more uniform dwell times generated by HIPO algorithm. The presented comparison may be used as a valuable hint for choosing the initial optimization method in planning the BT boost for breast cancer patients.

Dosimetric feasibility of an anthropomorphic three-dimensional PRESAGE® dosimeter for verification of single entry hybrid catheter accelerated partial breast brachytherapy

AbstractPurposeTo determine the feasibility of an anthropomorphic breast polyurethane-based three-dimensional (3D) dosimeter with cavity to measure dose distributions and skin dose for a commercial strut-based applicator strut-adjusted volume implant (SAVI™) 6–1.Materials and methodsAn anthropomorphic breast 3D dosimeter was created with a cavity to accommodate the SAVI™ strut-based device. 2 Gy was prescribed to the breast dosimeter having D95 to planning target volume evaluation (PTV_EVAL) while limiting 125% of the prescribed dose to the skin. Independent dose distribution verification was performed with GAFCHROMIC® EBT2 film. The dose distribution from the 3D dosimeter was compared to the distributions from commercial brachytherapy treatment planning system (TPS) and film. Point skin doses, line profiles and dose–volume histogram (DVHs) for the skin and PTV_EVAL were compared.ResultsThe maximum difference in skin dose for TPS and the 3D dosimeter was 4% whereas 41% between the TPS and EBT2 film. The maximum dose difference for line profiles between TPS, 3D dosimeter, and film was 4·1%. DVHs of skin and PTV_EVAL for TPS and 3D dosimeter differed by a maximum of 4% at 5 mm depth and skin differed by a maximum 1·5% between TPS and 3D dosimeter. The criterion for gamma analysis comparison was 92·5% at ±5%±3 mm criterion. The TPS demonstrated at least ±5% comparability in predicting dose to the skin, PTV_EVAL and normal breast tissue.Conclusions3D anthropomorphic polyurethane dosimeter with cavity gives comparable results to the TPS dose predictions and GAFCHROMIC® EBT2 film results in the context of HDR brachytherapy.

Impact of inter-observer variations in target volume delineation on dose volume indices for accelerated partial breast irradiation with multi-catheter interstitial brachytherapy

PurposeTo investigate dosimetric impact of inter-observer variation in clinical target volume(CTV) delineation for patients undergoing interstitial partial breast brachytherapy. MethodsFive radiation oncologists delineated CTV in twenty patients who underwent multi-catheter partial breast brachytherapy. Five treatment plans for each patient were graphically optimized for CTV of all observers and evaluated using coverage index(CI), external volume index(EI), overdose volume index(OI) and conformal index(COIN). In addition, volume enclosed by prescription isodose(V100), its spatial concordance(CIcommon), mean coverage of all CTVs with common volume of prescription dose(V100_common) and mean CTV coverage for all pairs of observer with common prescription volume of respective pairs(V100_pair) were also computed. ResultsThe mean ± standard deviation(SD) of CI and COIN ranged from 0.756 ± 0.076 to 0.840 ± 0.070 and 0.591 ± 0.090 to 0.673 ± 0.06 respectively. When a plan made for CTV of individual observer was evaluated on CTV of all observers, the maximum variations(ρ < 0.05) in the mean CI,COIN,OI and EI were 10.6%,11.4%,10.6% and 72.7% respectively. The observed mean ± SD of V100, CIcommon of V100, CTV coverage with V100_common and V100_pair was 160.7 ± 52.1, 0.70 ± 0.09, 73.1 ± 8.1% and 77.9 ± 7.3% respectively. ConclusionInter-observer variation in delineation of CTV showed significant dosimetric impact with mean CTV coverage of 73.1% and 77.9% by common and paired prescription dose volume respectively among all observers.

Subcutaneous Spacer Injection to Reduce Skin Toxicity in Breast Brachytherapy - A Pilot Study on Mastectomy Specimen

Subcutaneous Spacer Injection to Reduce Skin Toxicity in Breast Brachytherapy - A Pilot Study on Mastectomy Specimen