Multilumen Balloon Research Articles

Optimization of the accelerated partial breast brachytherapy fractionation considering radiation effect on planning target and organs at risk

The same fractionation scheme of accelerated partial breast irradiation (APBI) with brachytherapy is usually applied to APBI patients without considering the radiaton effect on the planning target and organs at risk (OARs) for an individual patient. The purpose of this study is to report the results of optimization of the fractionation scheme by evaluating the radiation effect on target and OARs with a modified linear-quadratic model, universal survival curve (USC), based on dose-volume histograms (DVHs). Ten breast patients treated with multilumen balloon brachytherapy were selected. The minimum skin and chest wall/rib (CW/rib) spacing ranged from 2.5 to 14.3 mm and from 0.5 to 25.0 mm, respectively. The USC model parameters were set as: (1) breast:α = 0.3, β = 0.05; (2) skin: acute reaction α = 0.101, β = 0.009; late reaction α = 0.064, β = 0.029; (3) CW/rib: α = 0.3, β = 0.12. Boundary dose Dt was 6 Gy for both target and OARs. The relation between radiation effects on the target (ET) and OARs (EOAR) were plotted for fraction numbers (N) from 1 to 20. If ET is set at a certain value, the fractionation that results in a minimum EOAR value corresponds to the optimal fractionation. The results show that the optimal fractionation is different for different OAR damage effects. For most of the patients, N = 2 is best for minimizing skin acute reactions while N = 20 is best for minimizing skin late reactions. N varies from 3 to 20 among patients for minimizing CW/rib toxicity. The determined unique optimal N for treatment delivery was found to vary from 1 to 20 among these 10 patients resulted from balancing the different damage effects considering the spatial dose for a given patient geometry. Optimal fractionation can be achieved for an individual patient by evaluating the radiation effect on tumor and OARs with the USC model based on the patient specific DVHs with APBI brachytherapy.

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.

Implementation of an HDR brachytherapy–based breast IORT program: Initial experiences

PurposeA multidisciplinary team at our institution developed a novel method of intraoperative breast radiation therapy (precision breast intraoperative radiation therapy [PB-IORT]) that uses high-dose-rate brachytherapy with CT on-rails imaging to deliver high-dose, customized radiotherapy to patients with early-stage breast cancer. This report summarizes our program's experience developing and implementing PB-IORT. Methods and MaterialsLiterature on PB-IORT was reviewed including published articles and abstracts. To evaluate case volume, all patients with a breast cancer diagnosis who underwent breast surgery or breast radiation (2010–2017) at our academic institution were identified. Patients were stratified into pre-IORT and post-IORT eras with initiation of our PB-IORT program in October 2013. Overall trends in surgical and radiation therapy volume in each era were analyzed by linear regression. Travel distance for all surgical patients was calculated using Google Maps (Alphabet Inc.) and then compared between IORT and non-IORT patients. ResultsData from a PB-IORT Phase 1 trial found that the primary endpoints were met and that PB-IORT is feasible and safe. The direct health system's delivery costs for PB-IORT exceed those of 16-fraction whole-breast irradiation when accounting for consumable supplies (multilumen balloon applicator = $2,750 per patient). There was a significant increase in yearly growth of breast cancer surgical volume with PB-IORT. ConclusionsAccrual rates for the ongoing Phase II trial have been quicker than expected in an area where more research is needed. The rapid accrual indicates patient interest and demand for this treatment and that it is very feasible to get more data from randomized trials.

Time-Driven Activity-Based Cost Analysis of CT-Guided Intraoperative High-Dose Rate Brachytherapy Versus Whole Breast Irradiation in the Treatment of Early Stage Breast Cancer

To evaluate the health care delivery cost of single fraction CT-guided intraoperative high-dose rate brachytherapy (HDR-IORT) in early stage breast cancer using time-driven activity-based costing (TDABC). Process maps were created for each step of the radiation treatment process at our institution for early stage breast cancer. The capacity cost from consultation to completion of radiation was calculated for personnel, equipment, and consumable resource. Personnel costs were calculated using individual personnel time and salary data. Equipment costs were calculated to include cost of CT-simulation, treatment planning software, and treatment machine time. Consumable costs were limited to resources specific to the individual radiation treatment (e.g. multi-lumen balloon) of each patient and did not include diagnostic, surgical, or anesthesia costs associated with lumpectomy alone as patients treated with whole breast irradiation (WBI) incurred similar costs. Patients are treated with HDR-IORT on an ongoing prospective trial. The procedure includes lumpectomy and placement of a multi-lumen balloon applicator by the breast surgeon. Intraoperative CT on-rails is utilized for image confirmation of catheter placement, treatment planning and delivery of 12.5 Gy to 1 cm from the balloon surface. In comparison, whole breast irradiation (WBI) alone consisted of 42.56 Gy in 16 fractions, with consideration of a 4 fraction boost. The total health care cost to deliver HDR-IORT for a patient was $4,875. The total cost to deliver WBI alone was $2,832, with an additional $363 for a 4 fraction boost. Radiation oncology personnel accounted for $1,909 (39%) and $1,658 (59%) of the total IORT and WBI cost, respectively. Surgical attending physician time required an additional 30 minutes to allow for balloon placement and image-guided confirmation in the brachytherapy suite. During HDR-IORT, the anesthesia team spent an additional 315 minutes (accounting for multiple team members). Radiation oncology attending time was 16% less for HDR-IORT compared to WBI, 91 minutes versus 108 minutes respectively. Equipment cost was $216 (4%) and $1,174 (41%) for the total cost of HDR-IORT and WBI, respectively. The cost of the multi-lumen balloon applicator ($2,750 per patient) represented 56% of the total IORT cost. TDABC analysis demonstrates a higher cost of delivery for treatment with HDR-IORT compared to WBI, largely due to increased consumable costs. Our calculated total delivery cost ($4,875), which exceeds the current payment rates for other forms of breast IORT, should be considered for reimbursement decisions. These findings exemplify that a streamlined process and dedicated team can result in efficient delivery of HDR-IORT.

Skin dose estimation using virtual structures for Contura Multi-Lumen Balloon breast brachytherapy

PurposeTo propose a workflow that uses ultrasound (US)-measured skin–balloon distances and virtual structure creations in the treatment planning system to evaluate the maximum skin dose for patients treated with Contura Multi-Lumen Balloon applicators. Methods and MaterialsTwenty-three patients were analyzed in this study. CT and US were used to investigate the interfractional skin–balloon distance variations. Virtual structures were created on the planning CT to predict the maximum skin doses. Fitted curves and its equation can be obtained from the skin–balloon distance vs. maximum skin dose plot using virtual structure information. The fidelity of US-measured skin distance and the skin dose prediction using virtual structures were assessed. ResultsThe differences between CT- and US-measured skin–balloon distances values had an average of −0.5 ± 1.1 mm (95% confidence interval [CI] = −1.0 to 0.1 mm). Using virtual structure created on CT, the average difference between the predicted and the actual dose overlay maximum skin dose was −1.7% (95% CI = −3.0 to −0.4%). Furthermore, when applying the US-measured skin distance values in the virtual structure trendline equation, the differences between predicted and actual maximum skin dose had an average of 0.7 ± 6.4% (95% CI = −2.3% to 3.7%). ConclusionsIt is possible to use US to observe interfraction skin–balloon distance variation to replace CT acquisition. With the proposed workflow, based on the creation of virtual structures defined on the planning CT- and US-measured skin–balloon distances, the maximum skin doses can be reasonably estimated.

A Single-Site Retrospective, Nonrandomized Study of Accelerated Partial Breast Irradiation Brachytherapy for Early-Stage Breast Cancer Treatment to Evaluate Local Tumor Control, Cosmetic Outcome, and Toxicities.

To evaluate the efficacy and safety of the accelerated partial breast irradiation brachytherapy with a combination of applicators at a community hospital cancer center. Between 2005 and 2009, 120 patients with early-stage breast cancer were being followed after treatment with accelerated partial breast irradiation brachytherapy using MammoSite, single or multilumen balloon, or Contura multilumen balloon. After their lumpectomy surgery, each patient was treated with Ir-192 high-dose rate unit following radiation therapy oncology group 0413 guidelines. The patients had multiple follow-ups at 6 months, 1 year, 2 years, 3 years, or more. Based on the Harvard Breast Cosmesis Scale, 95.00% of patients described their cosmetic evaluation as the treated breast essentially the same as the opposite side (excellent) or minimal but identifiable effects were noticed from radiation (good). After a median follow-up of 36 months, the local recurrence rate was 1.66% and a disease-free survival is 98.3%. Forty-two patients reported 85 adverse events, which were fibrosis: 24.70%, hyperpigmentation: 20.00%, radiation skin reaction: 7.05%, seroma: 7.05%, breast pain: 7.05%, erythema: 5.88%, and other events were less than 5.00%. Of all the adverse events recorded, grade 1 to 3 events are 95.29% (n = 81), 2.35% (n = 2), and 2.35% (n = 2). There was no grade 4 or 5 events recorded. Our study has shown promising results for delivering radiation with MammoSite, single or multilumen balloon, or Contura multilumen balloon and has been successful in achieving local control in patients with early-stage breast cancer.

SU‐F‐T‐01: Optimization of the Accelerated Partial Breast Brachytherapy Fractionation with Consideration of Physical Doses to Tumor and Organ at Risk

Purpose:The accelerated partial breast irradiation (APBI) with brachytherapy prescribes 34Gy to be delivered in 10 fractions over 5 consecutive working days without considering the physical dose to the target and organs at risk (OARs) for an individual patient. The purpose of this study is to optimize the fractionation scheme by evaluating the radiation effect on tumor and OARs with a modified linear‐quadratic (LQ) model based on dose‐volume histograms (DVHs).Methods:Five breast patients treated with multilumen balloon brachytherapy were selected. The minimum skin and rib spacing were ranged from 2.5mm to 14.3mm and from 1.0mm to 25.0mm, respectively. The LQ model parameters were set as: (1) breast: α=0.08, β=0.028, doubling time Tpot=14.4 days, and starting time Tk=21days; (2) skin: acute reaction α=0.101, β=0.009; late reaction α=0.064, β=0.029; (3) rib: α=0.3, β=0.12. Boundary dose Dt was 6 Gy for both target and OARs. The relation between radiation effects on the tumor (ET) and OARs (EOAR) were plotted for fraction number from 1 to 20.Results:The value of radiation effect from routine 3.4Gyx10 fractions was used as reference, ETref and EOARref. If set ET=ETref, the fractionation that results in minimum EOAR values correspond to the optimal fractionation. For these patients, the optimal numbers are 10 fractions for skin acute reaction, 18 fractions for skin and rib late reaction while the doses per fraction are 3.4Gy and 2.05–2.10Gy, respectively. If set EOAR=EOARref, the fractionation that results in a maximum ET value corresponds to the optimal fractionation. The optimal fractionation is 3.4Gyx10 fractions for skin acute reaction, and 2.10–2.25Gyx18 fractions for skin late reaction and rib.Conclusion:For APBI brachytherapy, the routine 3.4Gyx10 fractions is optimal fractionation for skin acute reaction, while 2.05–2.25Gyx18 fractions is optimal fractionation for late reaction of skin and rib.

A Novel Form of Breast Intraoperative Radiation Therapy With CT-Guided High-Dose-Rate Brachytherapy: Results of a Prospective Phase 1 Clinical Trial

Existing intraoperative radiation therapy (IORT) techniques are criticized for the lack of image guided treatment planning and energy deposition with, at times, poor resultant dosimetry and low radiation dose. We pioneered a novel method of IORT that incorporates customized, computed tomography (CT)-based treatment planning and high-dose-rate (HDR) brachytherapy to overcome these drawbacks: CT-HDR-IORT. A phase 1 study was conducted to demonstrate the feasibility and safety of CT-HDR-IORT. Eligibility criteria included age ≥50years, invasive or in situ breast cancer, tumor size <3cm, and N0 disease. Patients were eligible before or within 30days of breast-conserving surgery (BCS). BCS was performed, and a multilumen balloon catheter was placed. CT images were obtained, a customized HDR brachytherapy plan was created, and a dose of 12.5Gy was delivered to 1-cm depth from the balloon surface. The catheter was removed, and the skin was closed. The primary endpoints were feasibility and acute toxicity. Feasibility was defined as IORT treatment interval (time from CT acquisition until IORT completion) ≤90minutes. The secondary endpoints included dosimetry, cosmetic outcome, quality of life, and late toxicity. Twenty-eight patients were enrolled. The 6-month follow-up assessments were completed by 93% of enrollees. The median IORT treatment interval was 67.2minutes (range, 50-108minutes). The treatment met feasibility criteria in 26 women (93%). The dosimetric goals were met in 22 patients (79%). There were no Radiation Therapy Oncology Group grade 3+toxicities; 6 patients (21%) experienced grade 2 events. Most patients (93%) had good/excellent cosmetic outcomes at the last follow-up visit. CT-HDR-IORT is feasible and safe. This promising approach for a conformal, image-based, higher-dose breast IORT is being evaluated in a phase 2 trial.

WBRT vs. APBI: an interim report of patient satisfaction and outcomes.

PurposeTo determine differences in patient's reported quality of life and self-reported breast cosmesis between whole breast radiation therapy (WBRT) and accelerated partial breast irradiation (APBI) via single and multi-lumen high-dose-rate (HDR) brachytherapy for women with early stage breast cancer.Material and methodsPatient information was retrospectively reviewed and survey data were prospectively collected for women treated between 2004 to 2014 (APBI) and 2012 to 2014 (WBRT). Criteria for APBI treatments were ER+ (after 2010), N0 (after 2010), T < 3 cm, and post-menopausal. All patients were given a survey with modified FACIT (Functional Assessment of Chronic Illness Therapy) breast quality of life questions to rate their amount of pain, self-consciousness, low energy, presence of lymphedema, and breast cosmesis.Results242 APBI patients and 59 WBRT patients were identified. In the WBRT cohort, 34 women met departmental criteria for APBI treatment (WBRT who were APBI eligible). The FACIT survey was completed by 80 women treated with APBI (33%; mean follow-up time of 14 months), and 26 women treated with WBRT who were APBI eligible (76%; mean follow-up time of 26 months). During the first year post-treatment, low energy (p = 0.009), self-consciousness (p = 0.0004), and lymphedema (p = 0.0002) scores were significantly lower in the APBI cohort when compared to women treated with WBRT who were APBI eligible. During the second year post-treatment, women treated with APBI reported significantly better breast cosmesis (p = 0.04). The single-lumen balloon (score = 6.3/10) was found to be associated with worse cosmesis compared to the multi-lumen balloons (Mammosite ML and Contura; score = 8.2/10; p = 0.002). There were no significant differences in rates of recurrence between balloons or treatments (p > 0.05).ConclusionsAPBI treated patients reported higher cosmetic satisfaction than patients in the matched WBRT cohort. Quality of life scores tended to improve over time. Multi-lumen catheters provided superior cosmetic results compared to single-lumen catheters.

Dosimetric experience with 2 commercially available multilumen balloon-based brachytherapy to deliver accelerated partial-breast irradiation

The purpose of this work was to report dosimetric experience with 2 kinds of multilumen balloon (MLB), 5-lumen Contura MLB (C-MLB) and 4-lumen MammoSite MLB (MS-MLB), to deliver accelerated partial-breast irradiation, and compare the ability to achieve target coverage and control skin and rib doses between 2 groups of patients treated with C-MLB and MS-MLB brachytherapy. C-MLB has 5 lumens, the 4 equal-spaced peripheral lumens are 5mm away from the central lumen. MS-MLB has 4 lumens, the 3 equal-spaced peripheral lumens are 3mm away from the central lumen. In total, 43 patients were treated, 23 with C-MLB, and 20 with MS-MLB. For C-MLB group, 8 patients were treated with a skin spacing < 7mm and 12 patients with rib spacing < 7mm. For MS-MLB group, 2 patients were treated with a skin spacing < 7mm and 5 patients with rib spacing < 7mm. The dosimetric goals were (1) ≥ 95% of the prescription dose (PD) covering ≥ 95% of the target volume (V95% ≥ 95%), (2) maximum skin dose ≤ 125% of the PD, (3) maximum rib dose ≤ 145% of the PD (if possible), and (4) the V150% ≤ 50cm3 and V200% ≤ 10cm3. All dosimetric criteria were met concurrently in 82.6% of C-MLB patients, in 80.0% of MS-MLB patients, and in 81.4% of all 43 patients. For each dosimetric parameter, t-test of these 2 groups showed p > 0.05. Although the geometric design of C-MLB is different from that of MS-MLB, both applicators have the ability to shape the dose distribution and to provide good target coverage, while limiting the dose to skin and rib. No significant difference was observed between the 2 patient groups in terms of target dose coverage and dose to organs at risk.

Long-Term Results From the Contura Multilumen Balloon Breast Brachytherapy Catheter Phase 4 Registry Trial

To describe the long-term outcomes from a completed, multi-institutional phase 4 registry trial using the Contura multilumen balloon (CMLB) breast brachytherapy catheter to deliver accelerated partial breast irradiation (APBI) in patients with early-stage breast cancer. Three hundred forty-two evaluable patients were enrolled by 23 institutions between January 2008 and February 2011. All patients received 34 Gy in 10 fractions, delivered twice daily. Rigorous target coverage and normal tissue dose constraints were observed. The median follow-up time was 36 months (range, 1-54 months). For the entire patient cohort of 342 patients, 10 patients experienced an ipsilateral breast tumor recurrence (IBTR). Eight of these IBTR were classified as true recurrences/marginal miss (TRMM), and 2 were elsewhere failures (EF). Local recurrence-free survival was 97.8% at 3 years. For the entire cohort, 88% of patients had good to excellent overall cosmesis. The overall incidence of infection was 8.5%. Symptomatic seroma was reported in only 4.4% of patients. A separate analysis was performed to determine whether improved outcomes would be observed for patients treated at high-volume centers with extensive brachytherapy experience. Three IBTR were observed in this cohort, only 1 of which was classified as a TRMM. Local recurrence-free survival at high-volume centers was 98.1% at 3 years. Overall cosmetic outcome and toxicity were superior in patients treated at high-volume centers. In these patients, 95% had good to excellent overall cosmesis. Infection was observed in only 2.9% of patients, and symptomatic seroma was reported in only 1.9%. Use of the CMLB for APBI delivery is associated with acceptable long-term local control and toxicity. Local recurrence-free survival was 97.8% at 3 years. Significant (grade 3) toxicity was uncommon, and no grade 4 toxicity was observed. Treatment at high-volume centers was associated with decreased late toxicity.

A Single Site Prospective, Non-Randomized Study of Accelerated Partial Breast IrradiationBrachytherapy for Early Stage Breast Cancer Treatment to Evaluate Local Tumor Control, Cosmetic Outcome, and Toxicities

Breast Conservation Therapy (BCT) has become a standard treatment option for early stage breast cancer with multiple trials showing similar survival long-term to that of mastectomy. Breast brachytherapy treatment is considered as an alternative option compared to whole breast radiation and is a possible choice if criteria are met for early stage breast cancer. Our center has done Accelerated Partial Breast Irradiation (APBI) brachytherapy using either MammoSite™, single or multi-lumen balloon, or Contura™ multi-lumen balloon in the past several years and have followed up the patients for a median of 36 months after their treatment.

Day to day treatment variations of accelerated partial breast brachytherapy using a multi-lumen balloon.

PurposeTo evaluate the variations of multi-lumen balloon (MLB)-based brachytherapy from simulation day to treatment day and their dosimetric impacts during accelerated partial breast irradiation (APBI).Material and methodsA total of 42 CT images scanned from seven patients were evaluated with regards to daily variation due to of: 1) internal uncertainty: size and shape of balloon, seroma volume; 2) geometrical uncertainty-random: length of each catheter was measured for each fraction (total 70); 3) geometrical uncertainty-systematic: virtual systematic errors were tested by offsetting dwell positions. The original plans (as group A) had a mean value of 96.8% on V95 of the PTV_Eval. Plans were rerun (as group B) such that the mean value of the V95 was relaxed to 90.4%. By applying the reference plan to each daily CT image, variations of target coverage under different sources of error were evaluated.ResultsShape and size of the balloon had means of < 1 mm decreased in diameter and < 0.4 cm3 decreased in volume; the mean seroma volume increased by 0.2 cm3. This internal variation has a mean of < 1% difference for both V90 and V95. The geometrical uncertainty made a mean deviation of 2.7 mm per root of sum of square. It caused the degradations of V90 and V95 by mean values of 1.0% and 1.2%, respectively. A systematic error of 3 mm and 4 mm would degrade both of V90 and V95 by 4% and 6%, respectively. The degradations on target coverage of the plans in group A were statistically the same as those in group B.ConclusionsOverall, APBI treatments with MLB based brachytherapy are precise from day to day. However, minor variation due to daily treatment uncertainties can still degrade tumor bed coverage to an unacceptable coverage when V95 of the original plan is close to 90%.

Dosimetric evaluation of multilumen intracavitary balloon applicator rotation in high‐dose‐rate brachytherapy for breast cancer

The objective of this work is to evaluate dosimetric impact of multilumen balloon applicator rotation in high‐dose‐rate (HDR) brachytherapy for breast cancer. Highly asymmetrical dose distribution was generated for patients A and B, depending upon applicator proximity to skin and rib. Both skin and rib spacing was ≤0.7 cm for A; only rib spacing was ≤0.7 cm for B. Thirty‐five rotation scenarios were simulated for each patient by rotating outer lumens every 10° over ±180∘ range with respect to central lumen using mathematically calculated rotational matrix. Thirty‐five rotated plans were compared with three plans: 1) original multidwell multilumen (MDML) plan, 2) multidwell single‐lumen (MDSL) plan, and 3) singledwell single‐lumen (SDSL) plan. For plan comparison, planning target volume for evaluation (PTV_EVAL) coverage (dose to 95% and 90% volume of PTV_EVAL) (D95 and D90), skin and rib maximal dose (Dmax), and normal breast tissue volume receiving 150% (V150) and 200% (V200) of prescribed dose (PD) were evaluated. Dose variation due to device rotation ranged from −5.6% to 0.8% (A) and −6.5% to 0.2% (B) for PTV_EVAL D95; −5.2% to 0.4% (A) and −4.1% to 0.7% (B) for PTV_EVAL D90; −2.0 to 18.4% (A) and −7.8 to 17.5% (B) for skin Dmax; −11.1 to 22.8% (A) and −4.7 to 55.1% (B) of PD for rib Dmax, respectively. Normal breast tissue V150 and V200 variation was <1.0 cc, except for −0.1 to 2.5 cc (B) of V200. Furthermore, 30° device rotation increased rib Dmax over 145% of PD: 152.9% (A) by clockwise 30° rotation and 152.5% (B) by counterclockwise 30° rotation. For a highly asymmetric dose distribution, device rotation can outweigh the potential benefit of improved dose shaping capability afforded by multilumen and make dosimetric data worse than single‐lumen plans unless it is properly corrected.PACS number: 87.53.Jw

Dosimetric comparison between intra-cavitary breast brachytherapy techniques for accelerated partial breast irradiation and a novel stereotactic radiotherapy device for breast cancer: GammaPod™

The GammaPod™ device, manufactured by Xcision Medical Systems, is a novel stereotactic breast irradiation device. It consists of a hemispherical source carrier containing 36 Cobalt-60 sources, a tungsten collimator with two built-in collimation sizes, a dynamically controlled patient support table and a breast immobilization cup also functioning as the stereotactic frame for the patient. The dosimetric output of the GammaPod™ was modelled using a Monte Carlo based treatment planning system. For the comparison, three-dimensional (3D) models of commonly used intra-cavitary breast brachytherapy techniques utilizing single lumen and multi-lumen balloon as well as peripheral catheter multi-lumen implant devices were created and corresponding 3D dose calculations were performed using the American Association of Physicists in Medicine Task Group-43 formalism. Dose distributions for clinically relevant target volumes were optimized using dosimetric goals set forth in the National Surgical Adjuvant Breast and Bowel Project Protocol B-39. For clinical scenarios assuming similar target sizes and proximity to critical organs, dose coverage, dose fall-off profiles beyond the target and skin doses at given distances beyond the target were calculated for GammaPod™ and compared with the doses achievable by the brachytherapy techniques. The dosimetric goals within the protocol guidelines were fulfilled for all target sizes and irradiation techniques. For central targets, at small distances from the target edge (up to approximately 1 cm) the brachytherapy techniques generally have a steeper dose fall-off gradient compared to GammaPod™ and at longer distances (more than about 1 cm) the relation is generally observed to be opposite. For targets close to the skin, the relative skin doses were considerably lower for GammaPod™ than for any of the brachytherapy techniques. In conclusion, GammaPod™ allows adequate and more uniform dose coverage to centrally and peripherally located targets with an acceptable dose fall-off and lower relative skin dose than the brachytherapy techniques considered in this study.

SU-E-T-347: Dosimetric Effects Of Air Cavity Migration Through The Mammosite Multi-Lumen Balloon Treatments

Purpose: Study the dosimetric effects of air cavity migration through the mammosite multi-lumen balloon treatments. Methods: Using Multi-lumen mammosite had the advantage of shaping the dose around the balloon to get better coverage and less skin dose/hot spots. However, when there was air pocket around the balloon, the air pocket tended to move/change volume throughout the treatment. Since the dose distribution was usually asymmetric in treatment plans, the effects of air pocket need to be studied.Five(5) patients were selected for this study. For each patient, multi-lumen mammosite balloon was inserted into the cavity. Patient was then CTed and a treatment plan was created using Varian Eclipse TPS for delivery with Varian Varisource IX. PTV was created by expanding 1cm from balloon surface, 34 Gy were delivered in 10 fractions. The patient was CTed again after the last fraction before the balloon was extracted. The position of the balloon was checked to match the original CT. The treatment plan was recreated in the post-treatment CT.In order to evaluate the true difference, a new PTV was created in both original CT and post-treatment CT. The new PTV was 1 cm expansion from the cavity, excluding the entrance pathway, since these tissues were intended to be treated. Coverage and hot spots were evaluated with the new PTVs. Results: Through the treatment, air pocket normally will reduce volume and redistributed more evenly around the balloon, therefore coverage improved through the treatment. Since hot spots in multi-lumen cases were not symmetric, and during the planning, hot spots were usually targeted at air pocket if possible, at the end of the treatment, more tissue would receive high doses due to the air-pocket change. Conclusion: Care needs to be taken when there is air-pocket in treatment planning using multi-lumen mammosite treatment, especially the hot spots.

Dose modification factor analysis of multilumen balloon brachytherapy applicator with Monte Carlo simulation.

The Contura brachytherapy applicator is a silicone balloon with five lumens in which a high‐dose‐rate brachytherapy source can traverse. Multilumen applicators, like the Contura, are used in accelerated partial breast irradiation (APBI) brachytherapy in instances where asymmetric dose distributions are desired; for example, when the applicator surface‐to‐skin thickness is small (< 7 mm). In these instances, the air outside the patient and the lung act as a poor scattering medium, scattering less dose back into the breast and affecting the dose distribution. The recent report by Task Group 186 of the American Association of Physicists in Medicine (AAPM) has outlined the importance of moving towards brachytherapy dose calculations using heterogeneity corrections. However, at this time, many commercial treatment planning systems do not correct for tissue heterogeneity, which can result in inaccuracies in the planned dose distribution. To quantify the deviation in the skin dose we utilize the dose modification factor (DMF), defined as the ratio of the dose rate at 1 cm beyond the applicator surface with homogenous medium, to the dose rate at 1 cm with heterogeneous medium. This investigation models the Contura applicator with the Monte Carlo N‐Particle code version 5, and determines a DMF through simulation. Taking all geometrical considerations into account, an accurate model of the Contura balloon applicator was created in MCNP and used to run simulations. The dose modification factor was found to be only slightly dependent on whether the dose distribution was symmetric or asymmetric. These results indicate that the dose delivered to part of the PTV may be lower than the planned dose by up to 12%, and that these brachytherapy plans should be viewed with caution. In addition to studying the effects of backscatter, an evaluation was made regarding the capabilities of the Contura device to shape an asymmetric dose distribution. We compared these results to a previous study of a MammoSite ML and a SAVI device and found that the dose shaping capabilities of the Contura were quite similar to that of the MammoSite ML, but markedly inferior to the SAVI.PACS number: 87.53.Jw

The Value of Positron Emission Mammography (PEM) in Management of Breast Cancer

To determine the value of few key parameters measured from 3D-PEM breast images in breast cancer management. One hundred nine, pathology proven, female breast cancer patients with mean age of 66 ± 11 (ranging from 28 to 83) years underwent PEM imaging for surgical planning at our institute. Ten mCi of 18-flourodeoxy glucose (FDG) was administered intravenously. One hour post-injection, multiple tomographic sections of the right and left breast were obtained in medio-lateral, oblique and cranio-caudal (cc) positions. Retrospectively, lesion depth (using cc image), lesion size, lesion shape (ovoid, circular, irregular ovoid, irregular circular, ring-like, linear) and maximum standard uptake value (SUVmax) of FDG in lesion and normal fatty breast area was evaluated. The ratio of SUVmax of lesion to normal fatty breast area was computed. Whole body PET/CT FDG images were used for staging the breast cancer. Out of 109 patients 53.0% had left sided lesion and 47.0% were right sided. Seventy six percent of the patients had a single lesion and the remaining 24.0% had multiple lesions. The most common shape was found to be circular for 42.4% of the patients, 23.6% irregular circular, 21.2% irregular ovoid, 8.3% ovoid, 3.0% linear and 1.5% ring like. Less than 2.0% had a lesion depth of ≤ 0.7 cm. Remaining 98% had lesions at depths ranging from 0.9 cm to 10.8 cm with mean depth of 3.8 ±1.9 cm. All patients with lesions ≥ 0.7 cm were candidates for treatment with single lumen balloon catheter using Xoft E-brachytherapy system for accelerated partial breast irradiation (APBI). Patients with lesion depths ≤ 0.7 cm were candidates for multi-lumen balloon catheter. The average value for maximum PEM SUV (SUVmax) in the lesion was 1.49 ± 1.09 (ranging from0.46 to 7.48) and in normal fatty breast tissue was 0.25 ± 0.13(ranging from 0.07 to 0.90). The mean ratio of SUVmax of lesion to normal tissue was 6.35 ± 4.04 (ranging from 0.88 to 24.1). The number of metastatic lesions was determined from PET/CT images. Preliminary findings suggest a correlation of this ratio with staging of the breast cancer determined from whole body PET/CT scan of these patients. PEM imaging may provide valuable parameters such as accurate lesion depth measurement which in turn helps decipher the selection of single vs multi-lumen catheter for APBI. In addition to this the ratio of SUVmax may help predicting the stage and hence, prognosis and management of breast cancer.

Contura Multi-Lumen Balloon Breast Brachytherapy Catheter: Comparative Dosimetric Findings of a Phase 4 Trial

Final dosimetric findings of a completed, multi-institutional phase 4 registry trial using the Contura Multi-Lumen Balloon (MLB) breast brachytherapy catheter to deliver accelerated partial breast irradiation (APBI) in patients with early-stage breast cancer are presented. Three dosimetric plans with identical target coverage were generated for each patient for comparison: multilumen multidwell (MLMD); central-lumen multidwell (CLMD); and central-lumen single-dwell (CLSD) loading of the Contura catheter. For this study, a successful treatment plan achieved ideal dosimetric goals and included the following: ≥ 95% of the prescribed dose (PD) covering ≥ 95% of the target volume (TV); maximum skin dose ≤ 125% of the PD; maximum rib dose ≤ 145% of the PD; and V150 ≤50 cc and V200 ≤ 10 cc. Between January 2008 and February 2011, 23 institutions participated. A total of 318 patients were available for dosimetric review. Using the Contura MLB, all dosimetric criteria were met in 78.93% of cases planned with MLMD versus 55.38% with the CLMD versus 37.66% with the CLSD (P ≤.0001). Evaluating all patients with the full range of skin to balloon distance represented, median maximum skin dose was reduced by 12% and median maximum rib dose by 13.9% when using MLMD-based dosimetric plans compared to CLSD. The dosimetric benefit of MLMD was further demonstrated in the subgroup of patients where skin thickness was <5 mm, where MLMD use allowed a 38% reduction in median maximum skin dose over CLSD. For patients with rib distance <5 mm, the median maximum rib dose reduction was 27%. Use of the Contura MLB catheter produced statistically significant improvements in dosimetric capabilities between CLSD and CLMD treatments. This device approach demonstrates the ability not only to overcome the barriers of limited skin thickness and close rib proximity, but to consistently achieve a higher standard of dosimetric planning goals.

Can we improve the dose distribution for single or multi-lumen breast balloons used for Accelerated Partial Breast Irradiation?

PurposeThe aim of the study was to verify dose distribution parameters for multi-lumen, and artificially created single-lumen balloon applicator used for the same patient with two optimization algorithms: inverse planning simulated annealing (IPSA) and dose point optimization with distance option.Material and methodsGroup of 24 patients with multi-lumen balloon applied were investigated. Each patient received 10 fractions of 3.4 Gy (2 fractions daily). For every patient, four treatment plans were prepared. Firstly, for five-lumen balloon optimized with IPSA algorithm and optimization parameters adjusted for each case. Secondly, for the same applicator optimized with dose point optimization and distant option. Two other plans were prepared for single-lumen applicator, created by removing four peripheral lumens, optimized with both algorithms.ResultsThe highest D95 parameter was obtained for plans optimized with IPSA algorithm, mean value 99.3 percent of prescribed dose, and it was significantly higher than plans optimized with dose point algorithm (mean = 83.50%, p < 0.0001), IPSA single-lumen balloon plan (mean = 83.50%, p = 0.0037) and optimized to dose point single-lumen balloon (mean = 85.51%, p < 0.0001). There were no statistically significant differences concerning maximum doses distributed to skin surface for neither application nor optimization method. Volumes receiving 200% of prescribed dose in PTV were higher for multi-lumen balloon dose point optimized plans (mean = 8.78%), than for other plans (IPSA multi-lumen balloon plan: mean = 7.37%, p < 0.0001, single-lumen IPSA: mean = 7.20%, p < 0.0001, single-lumen dose point: mean = 7.19%, p < 0.0001).ConclusionsBasing on performed survey, better dose distribution parameters are obtained for patients with multi-lumen balloon applied and optimized using IPSA algorithm with individualized optimization parameters.