Partial Breast Irradiation Techniques Research Articles

Early Side Effects of Three-Dimensional Conformal External Beam Accelerated Partial Breast Irradiation to a Total Dose of 40 Gy in One Week (A Phase II Trial)

Several accelerated partial breast irradiation (APBI) techniques are described in the literature, and apparently, the three-dimensional (3D)-conformal technique is being used increasingly. Nonetheless, the optimal radiation dose is not yet known. Here, we report feasibility and early toxicities of APBI delivering 40 Gy over 5 days, in a phase II trial. From October 2007 to September 2008, 25 patients with pT1N0 cancer received 3D-conformal APBI. The prescribed radiation dose was 40 Gy in 4-Gy fractions given twice daily. This technique used two minitangents and an "en face" electron field. Toxicities were systematically assessed at 1, 2, and 6 months and then once every 6 months. The planning tumor volume for evaluation (PTV_EVAL) coverage was adequate: the mean dose to the PTV_EVAL was 41.8 Gy (range, 41-42.4 Gy). Mean doses to the ipsilateral lung and heart were 1.6 Gy (range, 1.0-2.3 Gy) and 1.2 Gy (range, 1.0-1.6 Gy), respectively. One and two months after completion of APBI, most patients had no or mild erythema (n=16 patients at 1 month; n=25 patients at 2 months); none of these patients developed moist desquamation. After a median follow-up of 12 months, only 1 patient had a significant moderate field contracture (grade 2). Other reported late toxicities were grade 1. 3D-conformal APBI (with two minitangents and an "en face" electron field) using a total dose of 40 Gy in 10 fractions twice daily over 5 days achieved appropriate PTV_EVAL coverage and offered significant sparing of normal tissue. Early tolerance was excellent.

Safety and efficacy of targeted intraoperative radiotherapy (TARGIT) for early breast cancer: First report of a randomized controlled trial at 10-years maximum follow-up.

LBA517 Background: After breast conserving surgery, 90% of local recurrences (LR) occur within the index quadrant. Hence, restricting the radiation therapy to the immediate area around the tumour bed after removal of the primary tumour may be adequate (Vaidya JS, et al. Br Cancer.1996;74:820-4) Methods: Having safely piloted a new technique of partial breast irradiation (Vaidya JS, Baum M, Tobias JS et al Ann Oncol 2001;12:1075-80) we launched the TARGIT-A trial in March 2000 comparing TARGIT vs. standard whole breast external beam radiotherapy (EBRT) after breast conserving surgery in patients ≥45 years with invasive duct carcinoma. LR was the primary outcome measure (core protocol: www.thelancet.com/protocol-reviews/99PRT-47 ). Trial accrual from 31 international centers is complete (n=2232), with 80% power to detect a difference in relapse rate of 2.5% - the non-inferiority margin. Results: Median age was 63 (IQR 57-69), median tumor size 13mm (IQR 9-18mm), lymph nodes 17%+ve. Median follow-up is 24.6 months (max 10 years). Wound breakdown or delayed healing were reported in 28 of the TARGIT group and 20 in the EBRT group (p=0.24). RTOG grade 3 toxicity (nil grade 4) was seen in 6 vs. 21 (p=0.004) respectively. Overall local toxicity was equivalent (34/1092 TARGIT v. 41/1096 EBRT, p=0.42). The Kaplan-Meier estimate of LR in the breast, was 0.31% (CI 0.08-1.26) for TARGIT versus 0.29% for EBRT (CI 0.07-1.16) at 24 months. Conclusions: In the TARGIT group, the radiotherapy toxicity was significantly lower than in the EBRT group, while the increase in wound complications was not statistically significant. This analysis suggests that at a median follow-up of 24 months the local control with TARGIT is comparable to EBRT. Longer term follow-up is essential and accrual in similar studies is encouraged. [Table: see text]

Patient's Fear of Radiation and Satisfaction following Permanent Breast Seed Implants

Purpose: A partial breast irradiation technique using 103Pd permanent breast seeds implant (PBSI) has been tested in a prospective Phase I/II trial and is currently offered in a multicenter Registry trial. When the protocol was developed some collaborators expressed concerns that patients might refuse having radioactive material permanently implanted into their breast. The objective of this study was to describe patient's satisfaction with the treatment and fear of radiation exposure for themselves and their family after PBSI.

251 Effect of breathing on contralateral breast doses in patients with breast carcinoma receiving radiotherapy

Several accelerated partial breast irradiation (APBI) techniques are described in the literature, and apparently, the three-dimensional (3D)-conformal technique is being used increasingly. Nonetheless, the optimal radiation dose is not yet known. Here, we report feasibility and early toxicities of APBI delivering 40 Gy over 5 days, in a phase II trial.From October 2007 to September 2008, 25 patients with pT1N0 cancer received 3D-conformal APBI. The prescribed radiation dose was 40 Gy in 4-Gy fractions given twice daily. This technique used two minitangents and an “en face” electron field. Toxicities were systematically assessed at 1, 2, and 6 months and then once every 6 months.The planning tumor volume for evaluation (PTV_EVAL) coverage was adequate: the mean dose to the PTV_EVAL was 41.8 Gy (range, 41–42.4 Gy). Mean doses to the ipsilateral lung and heart were 1.6 Gy (range, 1.0–2.3 Gy) and 1.2 Gy (range, 1.0–1.6 Gy), respectively. One and two months after completion of APBI, most patients had no or mild erythema (n = 16 patients at 1 month; n = 25 patients at 2 months); none of these patients developed moist desquamation. After a median follow-up of 12 months, only 1 patient had a significant moderate field contracture (grade 2). Other reported late toxicities were grade 1.3D-conformal APBI (with two minitangents and an “en face” electron field) using a total dose of 40 Gy in 10 fractions twice daily over 5 days achieved appropriate PTV_EVAL coverage and offered significant sparing of normal tissue. Early tolerance was excellent.

Dosimetric effects of air pocket sizes in MammoSite treatment as accelerated partial breast irradiation for early breast cancer

MammoSite brachytherapy system has been used as one of the accelerated partial breast irradiation (APBI) techniques since 2002. The clinical results from several clinical institutions had shown comparable treatment efficacy, cosmesis, and toxicity to other APBI techniques. During MammoSite treatment, air cavities had been one of the primary issues causing treatment cancellation or delay. With the tolerance of the air volume less than 10% of the total Planning Target Volume (PTV) set, there is still no data available to show the actual dose delivered to the breast tissue with the existence of the air pocket. In this paper, Monte Carlo N‐Particle version 5 (MCNP5) was used to model a hypothesis MammoSite phantom with different sizes of air pockets, and compared to the calculation results from the treatment planning system (TPS) without heterogeneous corrections. It was found that without heterogeneous corrections, the difference between the TPS and MCNP5 calculations in the air cavity surface doses and PTV point doses can be up to 2.02% and 3.61%, respectively, using the balloon and air pocket size combinations calculated in this paper. Based on the distance from the point of interest to the balloon surface, an approximate dose can be calculated using the linear relationship found in this study. These equations provide a quick and simple way to predict the actual dose delivered to the breast soft tissue located within the PTV. With the equation applied to the dose from the TPS, the dose error caused by the air pocket during MammoSite treatment can be reduced to a minimum.PACS number: 87.53.Jw

3-Year Follow-Up of the Partial Breast Irradiation Trial for DCIS Using the MammoSite® Brachytherapy Balloon Catheter.

Abstract Purpose: To report the 3-year median follow-up of a prospective Phase II partial breast irradiation (PBI) trial utilizing the MammoSite® interstitial balloon as the sole radiation therapy treatment after lumpectomy for ductal carcinoma in situ (DCIS).Materials and Methods: One hundred and thirty-three patients were enrolled from May 2003 through January 2006 to reach the 100-patient partial breast irradiation (PBI) target goal of 34 Gy in 10 fractions, 1 cm peripheral to the MammoSite® balloon surface, b.i.d. with Iridium192 HDR brachytherapy. The eligibility criteria were age 45, unicentric pure DCIS, mammographic size ≤3cm, negative margin of ≥1 mm, gross pathology size ≤5 cm, clinically node negative, post-lumpectomy mammogram absent of residual microcalcificaion. A USC/VNPI score was then calculated based on age, tumor size, margin width, and nuclear grade [ref: Silverstein MJ, Am J Surg 2003;186(4):337-343]. Placement of the balloon was performed at the time of lumpectomy or post-lumpectomy with a required minimum distance of the balloon surface to skin (skin bridge) of 5 mm. Data was collected at enrollment, at implant, 3 and 6-months, then yearly for local control, cosmesis (Harvard Scale), toxicity, adverse events, disease-free survival, cause-specific survival, and contralateral breast failure. Local recurrence is defined as either invasive or non-invasive within the target volume. Ipsilateral elsewhere recurrence (IER) is defined as invasive or non-invasive outside of the target volume.Results: Of the 133 patients enrolled, thirty-three were not treated for the following reasons: less than 5 mm skin bridge (n=13), poor cavity conformance (n=10), positive margin (n=3), microinvasion (n=3), MD decision (n=2), patient request (1), and other (1). The nuclear grade distribution of the tumors were: NG1(17%), NG2(44%), and NG3(39%). The mean age was 60.8 years. The mean tumor size was 10.6 mm; mean closest surgical margin was 6.8 mm (R=0.1-40mm); post-lumpectomy placement in 72%; mean skin bridge distance was 13 mm with 89% ≥7mm. No patients have been lost to follow-up, and at a median 3-year follow-up, the cosmetic results have been rated as excellent/good in 94 and fair in 6 patients. There have been only four recurrences, all non-invasive with the following histological patterns listed in the table below. One was an IER.Recurrence DetailsCase No.Months Since PlacementInvasiveUSC/VNPI ScoreOriginal Tumor GradeComedo Necrosis18No93Yes211No83No317No62Yes432No52Yes No serious adverse events were reported with an infection rate of 9% (7 breast infections; 2 cellulitis).Conclusion: This is the longest reported prospective Phase II study using a PBI technique for pure DCIS patients, and continues to demonstrate the efficacy of the MammoSite® balloon for treating pure DCIS breast tumors, with no new recurrences since our last report at SABCS 2007. All the recurrences were noninvasive, and had at least one or more risk factors of a high USC/VNPI score, high nuclear tumor grade, or had a comedo necrosis pattern. There have been no recurrences in nuclear grade 1 or 2 patients in the absence of a comedo necrosis pattern. The cosmesis also continues to be excellent or good long-term in 96% patients. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 952.

Utilization of Breast Conserving Therapy in Stage 0, I, II Breast Cancer Patients in New Jersey: An American College of Surgeons National Cancer Database (NCDB) Analysis

Utilization of Breast Conserving Therapy in Stage 0, I, II Breast Cancer Patients in New Jersey: An American College of Surgeons National Cancer Database (NCDB) Analysis

Radiothérapie du cancer du sein chez le sujet âgé

In Western countries, about 25% of breast cancers (BC) occur in women older than 70 years old. Local control is a crucial step to cure disease, because locoregional relapse (LRR) is a major risk factor of subsequent metastases. After mastectomy, radiotherapy (RT) confirmed a very high value (regardless of age) in several trials and meta-analyses, especially in case of high LRR risk factors (i.e. axillary nodal involvement). Globally, RT reduces LRR rates by 60–70% and also increases long-term survival rates by 8–9%. After breast conserving surgery, several trials and meta-analyses confirmed that RT decreases 10-year local recurrence rates from 20–25 to 5–8%. RT replacement by hormonal treatment leads to a significantly higher LRR rate. Hypofractionated RT schemes could usefully apply to elderly people, but partial breast irradiation techniques are still under investigation. Finally, all elderly fitted women should receive adjuvant RT according to general guidelines with optimal technique in order to avoid cardiotoxicity. Indeed, under-treatment has an unfavourable effect on long-term survival.

SU-FF-T-607: Immobilization, Treatment Planning and Treatment Delivery for Breast Irradiation with Protons

Purpose: To describe a technique for partial breast irradiation with proton beam radiotherapy.Method and Materials: A breast patient post lumpectomy is fitted with a special brassiere to reproducibly support the ipsilateral breast while compressing the contralateral breast. The patient then lies prone in a PVC half cylindrical pipe, supported from shoulder up and below the abdomen by foam bead cushions. The air from the cushions is evacuated resulting in rigid immobilization. The breast area is then immobilized with a urethane based foaming agent producing custom immobilization of the ipsilateral breast. Next, the patient undergoes a treatment planningCT scan of the thorax. The physician contours the tumor bed to include surgical clips and then contours organs at risk. A 3D conformal treatment plan is then developed. For every treatment, the patient is fitted with the treatment brassiere, and positioned prone in the custom immobilization device. Orthogonal and treatment angle diagnostic x‐ray images are taken prior to treatment and are compared with the treatment planning DRRs to reproduce the treatment position according to the plan. The titanium clips are used in the alignment process. At least two fields are treated each day delivering a daily dose of 4.0 cobalt Gray equivalent, and a total dose of 40 cobalt Gray equivalent in 10 fractions. Results: 60 patients have been treated so far. Immobilization procedure is highly reproducible. A comparison with a photon plan demonstrates the clear advantage of a protontreatment to spare the organs at risk, including a significant decrease in skindose.Conclusion: The immobilization procedure provides an accurate and reproducible breast positioning, and minimizes respiratory motion. The procedure has been well tolerated by most patients treated so far. Protons provide significant normal tissue sparing as compared to photontreatments and the clinical results look encouraging.

Counterpoint: Conformal external beam for accelerated partial breast irradiation

It has been hypothesized that partial breast irradiation (PBI) may offer local control equivalent to whole breast irradiation. This came from the observation that majority of in-breast recurrences occur either within or near the tumor bed (1). Randomized trials comparing conservative surgery alone with conservative surgery followed by breast irradiation for early invasive breast cancers suggest that the risk of recurrence outside the region of the tumor bed is similar to the risk of developing a contra-lateral breast cancer (1, 2). These observations suggest that the benefit of whole breast irradiation is mainly derived from the delivery of radiation to the breast tissue in the region of the tumor bed. Therefore, PBI in selected patients might be all what is needed to maintain acceptable local control. Accelerated PBI will make treatment more convenient to patients and might avoid critical structure toxicities. There have been multiple PBI techniques described. These could be divided into two groups: invasive and noninvasive techniques. Invasive techniques include interstitial brachytherapy (lowdose-rate [LDR] and high-dose-rate [HDR] (3e5)), intraoperative radiation (6e9), and intracavitary brachytherapy (MammoSite (10e14)). Noninvasive techniques include three-dimensional (3D) conformal external beam (15e17), proton beams (18), and intensity-modulated radiation therapy (IMRT) (19, 20). Each technique has its own advantages and disadvantages.

Accelerated partial breast irradiation technique for whole-breast radiotherapy: A concern

Accelerated partial breast irradiation technique for whole-breast radiotherapy: A concern

Dosimetric comparison of four different external beam partial breast irradiation techniques: Three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, helical tomotherapy, and proton beam therapy

Background and purpose As an alternative to whole breast irradiation in early breast cancer, a variety of accelerated partial breast irradiation (APBI) techniques have been investigated. The purpose of our study is to compare the dosimetry of four different external beam APBI (EB-APBI) plans: three-dimensional conformal radiation therapy (3D-CRT), intensity-modulated radiation therapy (IMRT), helical tomotherapy (TOMO), and proton beam therapy (PBT). Methods and materials Thirty patients were included in the study, and plans for four techniques were developed for each patient. A total dose of 30 Gy in 6 Gy fractions once daily was prescribed in all treatment plans. Results In the analysis of the non-PTV breast volume that was delivered 50% of the prescribed dose (PD), PBT (mean: 16.5%) was superior to TOMO (mean: 22.8%), IMRT (mean: 33.3%), and 3D-CRT (mean: 40.9%) ( p < 0.001). The average ipsilateral lung volume percentage receiving 20% of the PD was significantly lower in PBT (0.4%) and IMRT (2.3%) compared with 3D-CRT (6.0%) and TOMO (14.2%) ( p < 0.001). The average heart volume percentage receiving 20% and 10% of the PD in left-sided breast cancer ( N = 19) was significantly larger with TOMO (8.0%, 19.4%) compared to 3D-CRT (1.5%, 3.1%), IMRT (1.2%, 4.0%), and PBT (0%, 0%) ( p < 0.001). Conclusions All four EB-APBI techniques showed acceptable coverage of the PTV. However, effective non-PTV breast sparing was achieved at the cost of considerable dose exposure to the lung and heart in TOMO.

Tolerance and Acceptance Results of a Palladium-103 Permanent Breast Seed Implant Phase I/II Study

To test, in a prospective Phase I/II trial, a partial breast irradiation technique using a 103Pd permanent breast seed implant (PBSI) realized in a single 1-h procedure under sedation and local freezing. Eligible patients had infiltrating ductal carcinoma < or = 3 cm in diameter, surgical margin > or = 2 mm, no extensive intraductal component, no lymphovascular invasion, and negative lymph nodes. Patients received a permanent seed implant, and a minimal peripheral dose of 90 Gy was prescribed to the clinical target volume, with a margin of 1.5 cm. From May 2004 to April 2007, 67 patients received the PBSI treatment. The procedure was well tolerated, with 17% of patients having significant pain after the procedure. Only 1 patient (1.5%) had an acute skin reaction (Grade 3 according to the National Cancer Institute Common Toxicity Criteria). The rates of acute moist desquamation, erythema, and indurations were 10.4%, 42%, and 27%, respectively. At 1 year the rate of Grade 1 telangiectasia was 14%. The rate of skin reaction decreased from 65% to 28% when skin received less than the 85% isodose. According to a Radiation Therapy Oncology Group questionnaire, 80-90% of patients were very satisfied with their treatment, and the remainder were satisfied. One patient (1.5%) developed an abscess, which resolved after the use of antibiotics. There was no recurrence after a median follow-up of 32 months (range, 11-49 months). The feasibility, safety, and tolerability of PBSI compares favorably with that of external beam and other partial breast irradiation techniques.

Irradiation insterstitielle partielle et accélérée du sein de haut débit de dose : résultats préliminaires cliniques et dosimétriques sur 61 patientes

Purpose Among all the accelerated and partial breast irradiation (APBI) techniques, low then high dose rate, interstitial brachytherapy (HDIB) was the first to be used in this field. This study presents the preliminary clinical and dosimetric results of the APBI using HDIB, performed in Antoine Lacassagne Cancer Center of Nice. Patients and Methods From June 2004 to March 2008, 61 patients (37 primary tumors and 24 second conservative treatments after local recurrence) presenting with T1-2 pN0 non-lobular invasive breast carcinoma, underwent lumpectomy with sentinel lymph node dissection and intraoperative tube placement for HDIB. Dose distribution analysis, using dose–volume histograms, was achieved based on a postoperative CT scan. A comparative dosimetric study was performed between optimized (O) and non-optimized (NO) dose distribution. Then, based on conformal index calculation, a novel index was proposed taking into account not only the conformity but also the homogeneity of HDIB implant. An analysis of dose gradient impact on HDIB biological equivalence dose was also conducted. Statistical analysis used T test confirmed by Wilcoxon test for cohort including less than 30 patients. Results The comparative dosimetric analysis between O and NO dose distributions shown that conformity indexes (conformal index, conformal number, and D 90 %) were significantly increased after optimization. Improving conformity leads to increasing hyperdosage volumes ( V 150 % and V 200 %). A new index named conformity and homogeneity index (CHI) including V 150 % values, modified the conformal index. A total dose of 34 Gy, delivered through HDIB in 10 fractions over five days was biologically equivalent to 41.93 Gy assuming α/β = 4 Gy and 75.76 Gy if the dose gradient was considered in the calculation. Conclusions HDIB is considered as one of the best IPAS technique. HDIB allows dose distribution optimization, skin spearing and accurate clinical target volume definition. Furthermore, HDIB dose gradient could play a key role for breast cancer local control.

Multidwell Position MammoSite Brachytherapy Decreases Skin Toxicity, Preliminary Results of a Phase II Trial

The MammoSite catheter is a simpler brachytherapy method that allows partial breast irradiation (PBI) at more institutions, and has become a commonly used PBI technique. Preliminary studies of MammoSite brachytherapy reported Grade 2 or higher skin toxicity in 50% of patients, and a significant number of catheters had to be removed prior to treatment due to less than 5 mm skin distance. These trials utilized a “single dwell position” HDR technique. Our phase II trial aims to determine whether using a multiple dwell dose delivery method can decrease skin dose and subsequent skin toxicity from MammoSite breast brachytherapy while achieving similar or superior PTV coverage.

Dose Gradient Impact on Biological Equivalent Dose for Accelerated Partial Breast Irradiation using High Dose Rate Interstitial Brachytherapy

The NASB PB-39/RTOG 0413 phase III trial compares partial versus whole breast irradiation. Partial breast irradiation (PBI) techniques included external beam radiation therapy (EBRT), interstitial high dose rate brachytherapy (IHDRB) and MammoSite. The delivered doses are currently 38.5 and 34 Gy in 10 fractions over 5 days (10f/5d) for EBRT and IHDRB respectively. The purpose of this study is to investigate whether the two radiation modalities are biologically equivalent.

TU‐C‐351‐01: Design of Magnetic Resonance Imaging Protocol for Accelerated Partial Breast Irradiation in Prone Position

Purpose: Accurate delineation of tumor bed is prerequisite for an effective treatment of breast cancer with accelerated partial breast irradiation (APBI) technique. Magnetic resonance imaging (MRI) has high contrast mechanisms that could enable precise contouring of the lumpectomy cavity. We investigated practical issues pertinent to MR‐guided breast radiation therapy using customized pulse sequences. Method and Materials: Unilateral breast MR images were obtained from two healthy volunteers in prone position on a dedicated coil. Radiation therapists positioned the volunteers in reproducible setup using a waterproof marker. We acquired 6‐min 3D MR images to analyze setup uncertainty and fast 2D MR images of 0.5‐s temporal resolution to detect respiratory motion. An accurate 3D warping‐correction algorithm was evaluated and used to restore spatial fidelity from geometric distortions due to MR gradient non‐linearities. MR images of surgical clips as fiducial were obtained using pulse sequences designed to provide high signal from lumpectomy cavity. Results: Average breathing motion in the breast was found to be less than 0.5 mm in prone position. Setup deviations of 1 cm were observed between series of intended prone positioning. Rigid image registration based on local anatomy structure resulted in a residual error which was up to 5 mm at the peripheral region of the breast. Gradient‐induced non‐linearity led to 1 cm distortion in the uncorrected phantom image at the region 15 cm away from the main magnet axis. The 3D correction algorithm reduced the deviation to &lt; 1 mm. We observed 4 mm signal void artifacts of surgical clips. Conclusion: We obtained MR images of suitable quality from volunteers using pulse sequences customized for lumpectomy site identification. MR‐guided APBI in prone position would require 5 mm uniform expansion of clinical target volume with the employment of an appropriate on‐board imaging technique.

Comparison of scatter doses to the heart, lung, spleen and contralateral breast for whole and partial breast irradiation techniques

Purpose: Breast cancer is nowadays diagnosed at an earlier stage and the overall survival has improved. For these early stages, treatment includes a lumpectomy followed by breast radiotherapy (XRT) to ensure a local control similar to mastectomy. Several adjuvant radiation techniques are currently available including whole or partial breast XRT. XRT increases the risk of secondary cancer which might result from unwanted radiation scatter. The objective of this study is to compare the range of radiation scatter for different techniques of breast XRT and to discuss the clinical consequences.

Dosimetric comparison of partial and whole breast external beam irradiation in the treatment of early stage breast cancer

A dosimetric comparison was performed on external-beam three-dimensional conformal partial breast irradiation (PBI) and whole breast irradiation (WBI) plans for patients enrolled in the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-39/Radiation Therapy Oncology Group (RTOG) 0413 protocol at our institution. Twenty-four consecutive patients were treated with either PBI (12 patients) or WBI (12 patients). In the PBI arm, the lumpectomy cavity was treated to a total dose of 38.5 Gy at 3.85 Gy per fraction twice daily using a four-field noncoplanar beam setup. A minimum 6 h interval was required between fractions. In the WBI arm, the whole breast including the entirety of the lumpectomy cavity was treated to a total dose of 50.4 Gy at 1.8 Gy per fraction daily using opposed tangential beams. The lumpectomy cavity volume, planning target volume for evaluation (PTV_EVAL), and critical structure volumes were contoured for both the PBI and WBI patients. Dosimetric parameters, dose volume histograms (DVHs), and generalized equivalent uniform dose (gEUD) for target and critical structures were compared. Dosimetric results show the PBI plans, compared to the WBI plans, have smaller hot spots in the PTV_EVAL (maximum dose: 104.2% versus 110.9%) and reduced dose to the ipsilateral breast (V50: 48.6% versus 92.1% and V100: 10.2% versus 50.5%), contralateral breast (V3: 0.16% versus 2.04%), ipsilateral lung (V30: 5.8% versus 12.7%), and thyroid (maximum dose: 0.5% versus 2.0%) with p values < or = 0.01. However, similar dose coverage of the PTV_EVAL (98% for PBI and 99% for WBI, on average) was observed and the dose difference for other critical structures was clinically insignificant in both arms. The gEUD data analysis showed the reduction of dose to the ipsilateral breast and lung, contralateral breast and thyroid. In addition, preliminary dermatologic adverse event assessment data suggested reduced skin toxicity for patients treated with the PBI technique.

Clinical and dosimetric experience with MammoSite-based brachytherapy under the RTOG 0413 protocol.

MammoSite balloon brachytherapy is a relatively new technique for partial breast irradiation. The present paper focuses on the treatment planning, dosimetry, and quality assurance aspects of that treatment, based on the Radiation Therapy Oncology Group 0413 randomized prospective trial (RTOG 0413) protocol. We investigate the usefulness of evaluating implants for treatment appropriateness according to the full set of RTOG criteria as compared with the manufacturer's guidelines. We describe our methods to improve MammoSite balloon implants that would otherwise not comply with the protocol. The initially acquired computed tomography (CT) images are evaluated for tissue conformance, balloon surface–to–skin distance, and balloon symmetry. If the implant fails to meet the foregoing criteria, corrective action such as delay in the CT scan, balloon manipulation, or fluid volume adjustment is taken, and the patient is re‐scanned. If the corrective action appears to be successful, three dimensional treatment planning and dose–volume histogram analysis is performed to evaluate the geometric and dosimetric parameters with regard to the RTOG 0413 protocol. The evaluated parameters include• volume ratio of the lumpectomy cavity to the ipsilateral breast,• target volume coverage,• tissue–balloon conformance,• balloon symmetry,• minimal balloon surface–to–skin distance,• maximum skin dose, and• normal breast tissue dose–volume parameters V150 and V200.Among our implants, 21.7% did not initially meet the RTOG 0413 acceptance criteria. Asymmetry and poor conformance values reduce the target volume coverage, and so an implant with moderate conformance and asymmetry can be within the manufacturer's guidelines, but still not meet the RTOG criteria. Our intervention corrected all but one of the implants that failed to meet the criteria. Manipulating the cavity and adjusting the balloon volume may salvage an implant and meet the strict geometric and dosimetric criteria imposed by the RTOG 0413 protocol.PACS number: 7.53.Jw